1. Evaluation of Current and Newly Proposed Measures of
Intoxication and Impairment
Stuart Maclachlan
submitted in partial fulfillment of the requirements
for the award of Bachelor of Psychology (Honours)
School of Psychology
November 2014

2. ii
Deakin University
School of Psychology
I am the author of the thesis
entitled: Evaluation of Current and Newly Proposed Measures of Intoxication
and Impairment
submitted for the degree
of: Bachelor of Psychology (Honours)
and I agree to grant the Directors of Fourth Year in the School of Psychology
permission to make this thesis available for consultation, loan and limited copying in
accordance with Copyright Act 1968.
Signed: Date: 21 / 11 / 2014

3. iii
Deakin University
School of Psychology
Ethics Summary Statement
Project Number: DUHREC-H 2012-286
Project Title: PRAXIS: Pupillary Response Assessment of Intoxication Symptoms
We the undersigned declare that the above-named research project has been completed
as described in the Application for Ethics Approval and in accordance with the ethics
guidelines of Deakin University.
Researcher’s Name: Stuart Maclachlan
Signed: Date: 21 / 11 / 2014
Supervisor’s Name: A/Prof. Peter Miller
Signed: Date: 21 / 11 / 2014

4. iv
ACKNOWLEDGEMENTS
As author of this thesis I would like to thank both Peter Miller and Nic Droste for
their constant support and supervision throughout the project. Their advice and
limitless patience was greatly appreciated.
I would also like to acknowledge the research assistant team who worked into the
early hours of the morning collecting data across various night life venues; without
you this project would not have been possible.

5. v
TABLE OF CONTENTS
Chapter 1 Literature Review 1
1.1 Abstract 2
1.2 Introduction 3
1.3 Method 6
1.4 Results 7
1.5 Discussion 18
1.5.1 Alcohol and Current Measures of Intoxication 18
1.5.2 Alcohol and Pupilometry 20
1.5.3 Alcohol and the Colour-word Stroop Task 21
1.6 Conclusion 23
1.7 References 24
Chapter 2 Empirical Report 27
2.1 Abstract 28
2.2 Introduction 29
2.2.2 Current Measures of Intoxication and Impairment 29
2.2.3 Newly Proposed Measures of Intoxication and Impairment 31
2.2.4 Aim and Hypotheses of the Present Study 32
2.3 Method 33
2.3.1 Design and Procedure 33
2.3.2 Materials and Measures 33
2.3.3 Participants 36
2.4 Results 36
2.4.1 Preliminary Analyses 36
2.4.2 Influence of Alcohol Consumption over time 39
2.4.3 Effects of Alcohol on Measures of Intox & Impairment 39
2.5 Discussion 42
2.5.2 Number of Standard Drinks as a Predictor of Alcohol 43
Consumption
2.5.3 Influence of Alcohol Consumption over time 43
2.5.4 Alcohol Consumption of Pupillary Response 44
2.5.5 Stroop task Performance as a Measure of Impairment 44
2.5.6 Implications and Future Research 45
2.6 References 47

6. vi
LIST OF FIGURES
Figure 1.1: Search Results (PRISMA) 8
vii

7. LIST OF TABLES
Table 1.1: Summary of Reviewed Articles on the Effects of Alcohol on Various 9
Measures of Intoxication and Impairment
Table 2.1: Description of Pupil Functions 35
Table 2.2: Alcohol Consumption Frequencies of Participants by BAC and Number 37
of Standard Drinks
Table 2.3: Bivariate Correlation Matrix of Alcohol Consumption and Measures of 38
Intoxication & Impairment by Single time Point
Table 2.4: Descriptive Statistics and t-test Results for Measures of Intox/Impairment 39
and BAC over Pre-post Testing
Table 2.5: Univariate Analysis of Variance for Current/Newly Proposed Measures 41
of Intoxication & Impairment by BAC

8. CURRENT MEASURES OF
INTOXICATION 1
Chapter 1
The Effect of Alcohol on Pupillary Response and Performance on Stroop Colour-Word
Task: A Systematic Reivew of Current Meaures of Intoxication
Stuart Maclachlan
Student ID: 210706466
Supervisor: A/Prof Peter Miller
Campus: Waterfront, Geelong
Word Count: 3992
“I, the undersigned, declare that this Literature Review is less than the specified word
limit, and that it comprises original work and writing by me, and that due
acknowledgement has been made to all other material used.”
Signed: Date: 23 / 06 / 2014

9. CURRENT MEASURES OF
INTOXICATION 2
1.1 Abstract
Introduction: Alcohol abuse and missuse is a significant issue in the Australian
community, with severe health, psychological, and finanical implications.. The following
literature review critically evaluates current measures used to examine intoxication and
impairment, as well as newly proposed methods such as pupillary repsonse and the colour-
word Stroop test.
Methods: This paper is a systematic review of the following databases: Health Source-
Consumer edition; Health Source-Nursing/Academic edition; PsycARTICLES;
PsycEXTRA; Psychology and Behavioral Sciences Collection; PsycINFO; SOC Index;
MEDLINE; MEDLINE complete; PubMed; and Web of Science.
Results:A total of 1697 results were screened and 22 articles met the selection critera and
screening process. The articles obtained were published between 1978 and 2013, with half
of the studies having been published in the last ten years. Of the 22 articles found, three
related specifically to pupilometry and prolonged alcohol use, while one study examined
alcohol use and performance on the colour-word Stroop task specifically.
Conclusions: There is an underlying need to validate an observable measure of intoxication
which can be utilzed in licenced venues. Findings suggest that current measures of
intoxication are limited in their application within natural settings. Pupillary response and
Stroop testing show increasing potential, however more extensive research into these
measures is required.

10. CURRENT MEASURES OF
INTOXICATION 3
1.2 Introduction
Alcohol is one of the most used and readily available drugs in Australia, with the
National Health Survey (NHS) of 2007-08 finding that 2.1 million persons consumed
alcohol at what is considered risky or high levels in the longer term, 13.4% of those being
18 years or older (Australian Bureau of Statistics [ABS], 2012). There are severe economic
implications associated with such dangerous levels of consumption, the cost of alcohol to
Australian society in 2004-05 (e.g. health and hospital systems, lost workplace
productivity, road accidents, and crime) being estimated at $15.3 billion (Australian
Institute of Health and Welfare [AIHW], 2011). Even at small doses, alcohol has been
shown to impact on executive functioning, such as judgement of performance,
expectancies, attention, and reaction time (Guillot, Fanning, Bullock & McCloskey,
2010). In regards to patrons of licenced premises, this cognitive impairment has
consequences for particular decisions such as whether to drive whilst under the influence
of alcohol (Cromer, Cromer, Maruff & Synder, 2010) and also enhances the likelihood of
engaging in aggressive behaviour (Miller, Wells, Hobbs, Zinkiewicz, Curtis & Graham,
2014). In Australia, drink driving continues to be a leading cause of road fatalities and
injuries, contributing to 28% of fatalities on our roads (Transport Acident Commision
[TAC], 2012). Furthermore, research suggests that a significant proportion of assaults and
alcohol-related violence occur in or within close proximity to bars and nightclubs, higher
than any other setting (Haines & Graham, 2005).
To begin to address the various issues associated with alcohol consumption in the
night-time economy, there is a need for a standardised, validated measure for clearly
defining intoxication which can be effectively applied within licenced premises (Graham et
al. 2013). Enforcement of responsible service of alochol (RSA) and liquor licencing laws
is currently restricted by the difficulty involved in making accurate and reliable
assessments of intoxication through observation. Numerous studies suggest that observers
relying on limited, subjective signs of drunkeness are generally poor at predicting blood
alcohol concentration (BAC), even for professions which might be expected to possess a
greater ability in doing so, such as law enforcement officers or bartenders (Langenbucher
& Nathan, 1983; Brick & Carpenter, 2001). This is complicated primarily due to reliable
signs of drunkenness not typically being visible until considerably high BAC’s,
particularly if the person has a developed tolerance to alcohol which may mask the
physical identifiers of intoxication (Brick & Erickson, 2001). Slurred speech, staggering

11. CURRENT MEASURES OF
INTOXICATION 4
gait, and glazed eyes consist of the only reliable subjective predictors of higher
intoxication, however even these more obvious signs may be unoticed depending on the
environmental factors of the venue such as noise and subdued lighting (Perham, Moore,
Sheperd & Cusens, 2007). Consequently, there remains a substantial risk of bar staff
failing to identify and refuse service to already intoxicated and cognitively impaired
patrons.
A challenge facing the implementation of more accurate measures of intoxication is
that its likely unfeasible to introduce the majority of common sobriety testing into night
life settings (Graham et al. 2013). For instance, breathalyser tests which act as the basis for
roadside interventions would ultimately be impractical, as they require a minimum time
from the participant’s last drink in order to provide an accurate reading, hence relying on
the prolonged voluntary cooperation of the patron. Another disadvantage of breathalyser
testing is that it ignores important factors unique to the invidual such as tolerance and
fatigue, which are known to infleunce accuracy of intoxication assessment. Therefore,
what is required is a measure of impairment based on observation, which can be
administered quickly and consistently. Furthermore, if this measure can be found to also
correlate with objective measures such as BAC, this may provide a more validated
definition of intoxication (Graham et al. 2013).
Of the various standardised field sobriety tests (SFST), horizontal gaze nystagmus
(HGN) displays perhaps the most promise to meet this role, being regularly utilized by law
enforcement officers in the United States (Citek, Ball & Rutledge, 2003). An influential
study by Rubenzer (2011), which evaluated a battery of field sobriety tests regularly used
by officers in the field, found HGN to be the most reliable measure of identifying
intoxication. This method of testing functions as alcohol effects ocular movement via
neural pathways, inhibiting the smooth pursuit system and ability to maintain gaze,
resulting in involuntary jerking movements of the eye (Goding & Dobie, 1986). Research
suggests that HGN correlates highly with both BAC and cognitive impairment, and has
been demonstrated to be accurate at predicting BAC in experimental and natural settings
(Citek, Ball & Rutledge, 2003; Dixon, Clark & Tiplady, 2009). A drawback of HGN is that
it is ultimately a subjective measure which relies heavily on the ability and training of the
person conducting the test to be effective (Booker, 2001).

12. CURRENT MEASURES OF
INTOXICATION 5
A more recent measure with growing research to support its usefulness in
predicting alcohol-induced impairment is pupillary response. By examining differences in
pupil size at rest and when exposured to stress (i.e light), it has been found that notable
differences exist between alcoholics and non-alcoholics and the way their pupils respond
both when sober and intoxicated (Rubin, Gottheil, Roberts, Alterman & Holstine, 1978).
Impairment may possibly be derived from these observable changes in pupil behaviour, as
it is a function of the autonomic nervous system which regulates normal pupillary
response, which is consequently being disrupted by the presense of alcohol (Rubin,
Gottheil, Roberts, Alterman & Holstine, 1980). Pupilometry has the potential to improve
the accuracy of predicting impairment from BAC, as it is an objective measure of an
involuntary response, and through use of a pupilometer device there is less room for error
and missinterpretation of observation.
Much like BAC however, pupillary response is limited in the way that it can only
provide proportional inferences regarding the level of impairment experienced (Brick &
Carpenter, 2001). Therefore, the need exists to develop a measure which may draw specific
conclusions in regards to the cognitive impairment unique to the individual under
examination. One proposed measure which has little research dedicated to its use in
sobreity testing is the colour-word Stroop task. This test is used commonly to measure
executive functions such as concentration effectiveness, inhibitory control, and mental
flexibility, and has been used to assist in diagnosis of certain mental disorders such as
dementia and schizophrenia (Penner, Kobel, Stocklin, Weber, Opwis and Calabrese, 2012).
If the Stroop effect could be found to also relate to BAC, then it would mark a significant
step towards measuring rather than simply predicting alcohol-induced impairment. This
has been made possible to examine within the context of licened premises due to the
development of computersied Stroop tests, making it more realistic for patrons to complete
given the environment (Penner et al. 2012).
The aim of this present literature review is to synthesise the evidence surrounding
intoxication, alcohol-induced impairment, and the various measures used in examining
these factors. A critical analysis of currently used and newly proposed measures will be
conducted to evaluate their usefulness in determining intoxication and cognitive
impairment specific to the context of the night-time economy.

13. CURRENT MEASURES OF
INTOXICATION 6
1.3 Method
A systematic search of the following databases was conducted: Health Source-
Consumer edition; Health Source-Nursing/Academic edition; PsycARTICLES;
PsycEXTRA; Psychology and Behavioral Sciences Collection; PsycINFO; SOC Index;
MEDLINE; MEDLINE complete; PubMed; and Web of Science. A search of grey
literature was not included.
Four searches were conducted across each database, resulting in a total of twelve
searches. Due to the number of measures examined, various search terms were used to
provide each distinct topic its own search.
1. For examining self-rated intoxication: self-rated, OR self-assessed.
2. For examining observer-rated intoxication: physical symptoms, OR behavioural
symptoms, OR behavioural signs, OR observer rated, OR recognising
intoxication, OR identifying drunkenness, OR predicting intoxication, OR
judging intoxication.
3. For examining pupillary response: end-position nystagmus, OR nystagmus, OR
pupil reaction, OR pupil response, OR pupil automatic response to alcohol, OR
pupil dilation, OR pupil restriction, OR uncontrollable pupil response to
alcohol, OR pupillometr*, OR horizontal-gaze-nystagmus, OR horizontal gaze
nystagmus, OR HGN, OR automated standardised pupilometry, OR automatic
reactivity, OR pupil size, OR pupillary.
4. For examining the colour-word Stroop test: Stroop test, OR Stroop test color &
word test, OR stroop* AND validity, OR accurately, OR reliability, OR stand*,
OR norm*.
Each of these four searches was conducted in conjunction with a combination of
various search terms relating to alcohol and intoxication, which included: alcohol, OR
intoxicat*, OR impair*, OR drunk*, OR alcohol intoxication assessment, OR level of
intoxication, OR measuring intoxication, blood alcohol content, OR blood alcohol
concentration, OR blood alcohol level, OR "BAC.

14. CURRENT MEASURES OF
INTOXICATION 7
The inclusion criteria for articles included:
1. Full text available
2. Published between 1970 - 2014
3. Participants were aged 18 or older
4. Peer-reviewed, from academic journals
The exclusion criteria included:
1. Articles not directly relevant and abiding to the above inclusion criteria
2. Articles that did not refer specifically to either a) impairment caused by alcohol, b)
evaluation of current measures used for intoxication and impairment, c) the use of
pupilometry, or d) the use of the colour-word Stroop task.
3. Alcohol was consumed and measured in conjunction with other drugs
4. Participants who had a neurological or psychological condition
1.4 Results
The twelve searches conducted returned a total of 25,913 results. The initial
screening of abstracts for relevance found 46 potential articles (full-text, excluding
duplicates), from which 22 met the selection criteria (see Figure 1 for a PRISMA diagram
of the search process). The selected articles are summarised below in Table 1.

15. CURRENT MEASURES OF
INTOXICATION 8
Figure 1.1
Search Results (PRISMA)
Initial records identified through
database searching:
(n =25,913)
Records screened:
(n =1697)
Records excluded:
(n =1651)
Full-text articles
assessed for eligibility:
(n =46)
Records after inclusion
criteria applied:
(n =24,262)
Full-text articles excluded,
with reasons:
(n =24)
 Impairment not
alcohol induced (e.g.
schizophrenia) = 2
 Measuring other than
self-rated intoxication
(e.g. mood) 13
 Variations of Stroop
task, measuring other
than impairment= 3
 Unrelated eye tests
(e.g. vertical-gaze
nystagmus)= 3
 Review articles= 3
Studies included in
quantitative synthesis
(meta-analysis)
(n =22)

16. CURRENT MEASURES OF INTOXICATION 9
Table 1.1
Summary of Reviewed Articles on the Effects of Alcohol on Various Measures of Intoxication and Impairment
Author(s)
(Year)
Country Details of Study
Design
Research Question Sample
Characteristics
Measures used
(Independent
variable(s) [IV]
and Dependent
variable(s) [DV])
Findings Limitations
Current Measures of Intoxication
 Self-Reported
Kerr, Greenfield
and Midanik,
(2006)
California, USA Trend analyses,
three cross-
sectional surveys
To describe and
model the sources
of the variation
and trends in the
meaning of
subjective
drunkenness
N= 3707, (n=
1497 females, n=
2210 males)
IV: Quantity of
drinks, frequency
of drinking,
subjective rating
of drunkenness.
DV: Reported
number of drinks
The mean reported
number of drinks
to feel drunk
declined
significantly
between each
survey. Volume of
alcohol and heavy
drinking occasions
were associated
positively with the
number of drinks
to feel drunk.
Important factors
such as family
history of alcohol
dependence, body
weight, and
income not
included in
analyses.
Grant, LaBrie,
Hummer and Lac,
(2012)
California, USA Field study,
within-subjects,
repeated measures
To evaluate the
accuracy of
college student’s
guesstimates of
their BAC level
and drinking
behaviours within
social settings
N= 305, (n= 98
females, n= 127
males) Mean age=
20.2 years (SD=
1.26)
IV: Level of BAC
DV: BAC
misperception
Participants at
lower levels of
intoxication tended
to slightly
overestimate their
BAC level.
Non-
representative of
general college
population.

17. CURRENT MEASURES OF INTOXICATION 10
Gengo, Gabos,
Straley and
Manning, (1990)
New York, USA Randomized,
double-blind,
placebo-
controlled, four-
way crossover
design
To assess the
effects of alcohol
on objective test
performance and
self-rated
impairment
N= 20, (males
only)
IV: Placebo or
alcohol group
DV: Estimated
BAC (Est.BAC),
digit symbol
substitution
(DSS), simulated
driving reaction
time (SDRT),
choice reaction
time (CRT), and
self-assessment of
impairment (SRI)
Subjective
impairment ratings
were greater while
alcohol
concentrations
were increasing,
compared to when
falling. Disparities
between SRI and
reduction in test
performance were
greatest at an hour
after peak
Est.BAC.
Only males tested.
Cromer et al.
(2010)
Connecticut, USA Single-blind,
randomized,
placebo-
controlled,
crossover within-
subjects design
To investigate
effects of alcohol
on subjective
intoxication and
executive
functions through
declining BAC
N= 20, (n= 11
females, n= 9
males) Mean age=
22.8 years (SD=
1.10)
IV: Placebo or
alcohol group
DV: Subjective
intoxication
rating,
computerized
maze task
(GMLT), BAC
Executive
functions and short
term memory
showed no
recovery from
alcohol impairment
when comparing
results from
ascending and
descending limbs
of the BAC curve.
Not double-blind.
 Observer-Reported
Perham et al.
(2007)
United Kingdom Field survey,
random sample,
control group,
within-subjects
To examine the
relationship
between BAC and
predictors of
impairment from
sobriety testing
N= 893, (n=314
females, n=579
males)
IV: intoxicated or
non- intoxicated
respondents
DV: BAC,
surveyors scores
on gait
Slurred speech,
staggering gait and
glazed eyes, in
combination,
predicted levels of
BAC significantly.
No blinding, field
study.

18. CURRENT MEASURES OF INTOXICATION 11
Olson, Smith,
Kloss, Ho and
Apple, (2013)
Minneapolis, USA Field study,
convenience
sample, within-
subjects
To assess the
accuracy of health
care personnel’s
ability to estimate
BAC from
physical signs and
symptoms of
intoxication
N= 384, (n= 77
females, n= 307
males) Mean age=
41 years
IV: NOT
REPORTED
DV: Estimated
BAC, actual BAC
Measured BAC
does not correlate
well with the
outward physical
signs of
intoxication,
especially for
chronic drinkers.
No control group.
Bellis, Hughes,
Quigg, Morleo and
Lisboa, (2010)
United Kingdom Cross-sectional
field survey,
random sample,
within-subjects
To examine the
relationship
between drinking
behaviour,
observable signs
of intoxication,
and BAC
N= 214 IV: NOT
REPORTED
DV: Breath
alcohol test
(BrAT)
Higher levels of
BAC strongly
correlate to
observational
sobriety measures
and self-assessed
drunkenness.
Higher blood
alcohol levels were
related to drink
later into the night.
No participant
gender
information
provided.
Rosenberg and
Nevis (2000)
Ohio, USA Experimental with
control group,
single blind,
between-subjects,
pre-post test
Effect of training
on assessing and
recognition of
intoxication by
university students
N= 45, (n= 33
females, n= 12
males) Mean age=
20.6 years
IV: Training or
placebo group
DV: Correct
identification of
target status
Participants in the
training program
had a higher mean
number of accurate
ratings of target
status compared
with the attention-
placebo control
group.
Not double-blind.
 Horizontal Gaze Nystagmus (HGN)
Goding and Dobie
(1986)
Washington, USA Field study,
convenience
sample, within-
subjects
To determine if
HGN can be used
to accurately
predict the BAC
N= 46, (n= 9
females, n= 37
males)
IV: NOT
REPORTED
DV: Angle of
onset horizontal
There were no
cases in which
BAC was
incorrectly
No control group.

19. CURRENT MEASURES OF INTOXICATION 12
of patients at an
emergency room
gaze nystagmus
(AON), BAC
estimated to be
>.10 in the absence
of other drugs
using HGN. A
correlation of .878
was found between
estimated and
actual BAC in DUI
suspects.
Citek et al. (2003) Oregon, USA Experimental pre-
post test,
convenience
sample, within-
subjects
To assess the use
of HGN testing
under various
conditions by law
enforcement
officers
N= 96, (n= 37
females, n= 59
males)
IV : Alcohol
dosage
DV : HGN and
VGN in various
positions
The HGN test
administered in the
standing, seated,
and supine
postures is able to
discriminate
impairment at
criterion BACs of
0.08% and 0.10%,
making it an
accurate test of
impairment
regardless of the
driver’s position.
Not replicated
under real-life
settings.
Booker (2001) Houston, USA Experimental,
random sample,
within-subjects,
repeated measures
To examine the
validity of the
HGN test when
administered by
police officers
under real life
conditions
N= 89 (n= 10
females, n= 79
males) Mean age
= 34 years
IV: Alcohol
dosage
DV: HGN, BAC
HGN has a high
baseline error and
a dose/response
relationship which
varies greatly
depending on
whether subjects
BAC is rising or
falling.
No control group.
Dixon et al. (2009) United Kingdom Two-period
crossover design,
placebo
controlled, double
To compare a
portable
impairment testing
N=122, (n= 60
males, n= 62
females)
IV: Placebo or
alcohol group
DV: Accuracy of
both test batteries
RITA had an
accuracy of
between 66 and
70%. This was
Only tested at a
BAC above the
legal driving limit.

20. CURRENT MEASURES OF INTOXICATION 13
blind and
randomised
device (RITA) to
field testing (FIT)
comparable to the
accuracy of the
FIT which was
62.7%. HGN had
an accuracy of
74% and was
found to be the
most accurate.
Pupilometry and Intoxication
Fotiou,
Fountoulakis,
Goulas,
Alexopoulos and
Palikaras, (2000)
Greece Standardisation of
two experimental
conditions for
pupilometry,
repeated measures
To identify the
usefulness of two
different methods
of pupilometry in
a clinical setting
N=50, (n=29
females, n=21
males)
IV: One flash or
repeated flash
method
DV: Ratio of pupil
to iris, ratio of
pupil radius to
baseline pupil
radius, iris
diameter, latency
for constriction,
amplitude and
latency of largest
deviation, latency
and amplitude of
plateau, duration
of constriction,
number of
oscillations
Able to determine
means and
standard deviations
of variables
characterising
normal pupil
response. The
combined use of
both types of
pupilometry
methods may be a
useful tool in
medical research,
by comparing
baseline of healthy
pupil response to
that of someone
suffering
alcoholism.
Since these
comparisons were
not actually made,
difficult to
comment with
certainty how
effective these
methods are as
diagnostic tools
for disease –
further research is
needed.
Richman,
McAndrew, Decker
and Mullaney,
(2004)
Massachusetts,
USA
Comparative
design,
randomized,
within-subjects
To evaluate the
current pupil
range criteria as
an indicator of
impairment in
N=250, Mean
age= 29.2 years
(SD=6.1)
IV: Lighting level
of room during
testing
DV: Pupil
measurements
The DEC pupil
range currently
used (3.0 to
6.5mm) may be too
sensitive, as results
Sample non-
representative of
the general
population.

21. CURRENT MEASURES OF INTOXICATION 14
Drug evaluation
and classification
(DEC) program
from non-impaired
participants fell
within a similar
range (3.86 to
6.41mm), making
it difficult to
discriminate
between normal
and impaired.
Rubin (1980) Pennsylvania,
USA
Experimental with
control group,
randomised,
between-subjects
To examine if
pupillary
measurements are
indicative of
sympathetic and
parasympathetic
activity in
alcoholic patients
N=35, (n=4
females, n=31
males)
IV: alcohol
dependent or
control group
DV: Pupillary
light and dark
reflexes
Alcoholics who
chose to drink
during the session
had the slowest
slower pupil
reactions and
highest attenuation
compared to
alcoholics who
chose not drink,
and non-alcoholics.
Women only used
in control group.
Rubin et al. (1980) Pennsylvania,
USA
Experimental,
randomised,
between-subjects
To examine
pupillary activity
in recovering
alcoholics and
non-alcoholics, in
various conditions
N=16, (n= 4
females, n=12
males)
IV: Alcoholic or
non-alcoholic,
abstained or had
not abstained,
during rest or
stress
DV: Pupillary
dilatation and
constriction
There was an
insignificant
difference between
alcoholics and non-
alcoholics at rest
for pupil response.
Alcohol
significantly
affected the light
reflex in alcoholics
and non-alcoholics
(p<.05). Alcohol
increased
sympathetic
response to stress
and recovery in
alcoholics.
Women only
included in the
non-alcoholic
condition, small
sample.

22. CURRENT MEASURES OF INTOXICATION 15
Rubin et al. (1978) Philadelphia, USA Experimental with
control group,
randomised,
between-subjects
Effects of stress
on autonomic
activity in
alcoholics
N=35, (n= 10
controls, n= 25
alcoholics) Mean
age= 28.5 years
IV: Alcohol
dependent or
control, rest or
stress
DV: Pupillary
dilatation and
constriction
Alcoholics with no
alcohol in their
system have
deficient reactivity
from their
autonomic nervous
system.
Alcoholics’
response to stress
was attenuated and
recovery was faster
than for non-
alcoholics.
No information
given regarding
gender.
Colour-Word Stroop Task and Impairment
Curtin and
Fairchild (2002)
Wisconsin, USA Experimental with
control group,
randomized,
within-subjects
To determine if
impaired
executive
attention is
responsible for
observed
behaviour deficits
when intoxicated
N= 48, (n= 24
females, n= 24
males)
IV: Alcohol
dosage or control
DV: Stroop task
performance
(accuracy and
response time), P3
magnitude
Alcohol produced
the largest increase
in error rate and
response time in
colour naming of
incongruent
stimuli. Also,
alcohol did not
affect P3
magnitude,
indicating that
timing of stimulus
evaluation
remained intact.
No blinding.
Gustafson and
Kallmen (1990)
Sweden Single-blind,
randomized,
placebo-
To examine
impairing effects
of alcohol on
performance of a
N= 48, (n= 24
females, n= 24
males) Mean age=
IV: Alcohol,
placebo, or control
group
Alcohol group
made more errors
and needed longer
to complete the
Highest BAC
recorded <.10 and
only social
drinkers were used

23. CURRENT MEASURES OF INTOXICATION 16
controlled, within-
subjects
complex cognitive
task, measured
using Stroop’s
Colour Word Test
27.7 years (SD=
7.6)
DV: total time
needed to
complete test,
number of
incorrect
responses, number
of hesitations
task. There was a
significant
interaction
between alcohol
dose by sex and
these two
measures,
indicating the
detrimental effect
of alcohol over
time was restricted
to women.
in sample, making
this study
unrepresentative
of the intoxication
reached in
licenced venues.
McKinney, Coyle
and Verster, (2012)
United Kingdom Repeated
measures,
counterbalanced,
random sample,
between-subjects
To compare
performance
measures after
acute alcohol
consumption
(intoxication) with
the performance
the day after a
normal night’s
drinking
(hangover).
N=84, (n= 51
females, n= 33
males
IV: Alcohol
consumption or no
alcohol
consumption
DV: Free recall
task, reaction time
task, divided
attention task,
selective attention
test, the Stroop
test, spatial
attention task.
Alcohol
consumption,
either acute or the
next day,
significantly
affected reaction
time, divided
attention, selective
attention and
Stroop
interference.
Use of
standardized
psychological
tasks that may not
translate to the
real world.
Penner et al. (2012) Switzerland Experimental,
randomized,
cross-over design
To assess the
validity of
computerised
Stroop tasks when
compared to the
original task
performance
N= 40, (n= 33
females, n= 7
males) Mean age
= 25 years (SD=
5.85)
IV: Original, or
computerised
versions of Stroop
task.
DV: Performance
on Stroop task
All three versions
show high test–
retest reliability
and are able to
elicit interference
effects, but to
varying degrees.
However,
performances in
the computerized
versions and in the
original task do not
correlate.
Sample size of the
two groups are not
equal.

24. CURRENT MEASURES OF INTOXICATION 17
Gualtieri and
Johnson, (2006)
New York, USA Longitudinal
study, random
sample, between-
subjects
To examine the
reliability and
validity of CNS
vital signs battery
(CNSVS), which
includes the
colour-word
Stroop task.
N= 1069 IV: NOT
REPORTED
DV: Verbal and
visual memory,
finger tapping,
symbol digit
coding, the Stroop
test, shifting
attention test,
continuous
performance test
The CNSVS test
battery achieved
high test-retest
reliability,
concurrent, and
discriminant
validity, proving
its usefulness in
screening, but not
diagnosis of
neuropsychological
disorders.
No gender or
specific age
information
regarding
participants.

25. CURRENT MEASURES OF
INTOXICATION 18
1.5 Discussion
1.5.1 Alcohol and Current Measures of Intoxication and Impairment
Twelve of the studies retrieved examined intoxication and alcohol-induced
impairment in relation to a number of common measures used within night time settings by
patrons, licenced alcohol servers, and law enforcement officers. Specifically, key findings of
these studies pertain to the limitations associated with making accurate judgements of self-
intoxication and observing the drunkenness of others, as well as an evaluation of the
reliability of HGN as a sobriety test in practical settings.
Evidence suggests that individuals are generally poor at making self-reported
assessments of their own level of intoxication. Typically, a person who falls within low levels
of intoxication (i.e. a BAC between 0 - .08) is slightly more likely to overestimate their actual
BAC, whilst someone at a higher level (i.e. .16+) is more likely to sizeably underestimate
their BAC (Grant et al. 2012). This finding is in line with current trends in alcohol
consumption observed by Kerr et al. (2006), indicating that volume of alcohol intake and
heavy drinking occasions are associated with the subjective perception of needing to drink
larger amounts to achieve a feeling of inebriation. Self-ratings of cognitive impairment are
influenced by the direction of the persons BAC level, with greater impairment reported by
those as BAC increased, and lesser as it decreased (Gengo et al. 1990). Despite how drunk or
sober a person may feel, there is contradictory evidence to suggest that actual executive
functioning including short-term memory and judgement remains impaired and shows no
recovery, regardless of the direction of BAC level (Cromer et al. 2010). In other words,
cognitive impairment caused by intoxication does not improve at the equivalent rate of
sobering up, despite this being a regular belief amongst patrons. These findings have a range
of implications for individuals who intend on a late night of drinking. Firstly, if a patron who
is already highly intoxicated perceives their drunkenness as lower than it already is, then it is
likely that they will continue to consume alcohol at what is considered risky or dangerous
levels. Secondly, as alcohol induced impairment maintains regardless of decreasing BAC,
this has severe consequences in that the person is unable to acknowledge that their decision
making is still inhibited. This is likely to influence poor choices such as acting out in
unwarranted aggressive behaviour. With this in mind, there is an underlying need for greater
responsibility of service of alcohol in licenced venues. This could be achieved by facilitating

26. CURRENT MEASURES OF
INTOXICATION 19
capable assessment and decision-making in bar staff and security through implementing new
and improved measures of intoxication.
Making outward observations of another person’s intoxication and impairment carries
more mixed findings across the retrieved studies. As BAC increases, so is the likelihood of
correctly assessing an individual’s level of impairment (Bellis et al. 2010). This is due to
certain physical symptoms which are considerably easy to identify and are consistently
associated with a certain level of BAC. Combinations of slurred speech, staggering gait, and
glazed eyes usually occur in over 50% of drinkers with a BAC of around .15, while almost all
(>84%) will show these physical signs at BAC of .20 or greater (Brick & Erickson, 2009;
Perham et al. 2007). However, contradictory findings in a study by Olson, Smith, Kioss, Ho
and Apple (2013) found that the predictive value of estimating BAC from alcohol-related
physical symptoms decreased from 93% accuracy at .10, to only 37% accuracy once a
participant’s BAC reached .30, demonstrating that measured BAC does not correlate well
with physical signs of intoxication. Tolerance is likely to have influenced this result, as it
possesses an ability to mask physical symptoms which are usually observable, therefore
making a chronic drinker appear far less impaired than they actually are. (Olson et al. 2013).
This leads to underlying issue being that a vast majority of intoxication is not visible, and
occurs at stages well before reliable physical symptoms begin to emerge. (Brick & Erickson,
2009) With the legal driving BAC limit at .05, this has drastic consequences for someone
needing to assess whether another person is capable of driving. These implications carry over
to bartenders in licensed venues, who may fail to identify a person who is already highly
intoxicated and continue service to them. Evidence from one particular study demonstrated
that with sufficient training, recognition ability can be improved to better assess BAC’s
between .05-.09, however this effect did not carry over in the long term at follow up
(Rosenberg & Nevis, 2000). This suggests the need for not only a re-evaluation of RSA
training and improved on-going education regarding tolerance and its effects, but for better
measures which may be utilized by bar staff and security to assist in accurate detection of
patron intoxication.
HGN has already demonstrated its usefulness in identifying intoxication across a
range of settings, being part of a recognised field sobriety test battery in the United States
since the 1980s. When compared against a field impairment test (FIT) battery consisting of
five individual tests, and a newly proposed measures known as the roadside impairment
testing apparatus (RITA), HGN still held the highest accuracy of 74%, and was found to be

27. CURRENT MEASURES OF
INTOXICATION 20
the most reliable (Dixon, Clark & Tiplady, 2009). Evidence shows that HGN testing when
conducted by police officers is able to discriminate impairment from BAC levels as low as
.08, regardless of the participant’s position, being standing, seated, or lying down (Citek, Ball
& Rutledge, 2003). A similar effect was found when conducted on patients in a hospital
setting, in which there was not a single case of BAC being incorrectly estimated to be greater
than .10 (Goding & Dobie, 1986). Ultimtately, there are a number of key issus which prevent
HGN from otherwise being an effective measure of improving detection of intoixcation
within licened venues. A reported limitation is that response from HGN can vary depending
on the direction of the person’s BAC and whether it is increasing or decreasing, making it
difficult to draw accurate conclusions of current impairment (Booker, 2001). Further,
considering that HGN is also a symptom of fatigue, and that testing would be conducted late
at night, there is an increased chance of false positive reportings if implemented into the
night-time economy (Rubezner, 2008). HGN still remains vulnerable to a multitude of
confounding variables likely to be present in real-world testing scenarios, such as the quality
of lighting in the venue, and the skills and training of the person conducting the test. If
bartenders or venue security were to be responsible for conducting this test on patrons, then
interpretation of results would be further confounded by personal drinking paterns, economic
motivation of the establishment, and management policies and practice (Reiling &
Nusbsumer, 2006). Therefore, a more objective measure based on observation is required to
be sucessful in predicting intoxication and impairment, particularly in licenced venues.
1.5.2 Alcohol and Pupilometry
Five of the studies obtained related to pupil response and how it is effected by alcohol
consumption, both immeadiately and in the long term. More specifically, the validity and
reliablity of pupil response as a measure of impairment is assessed, leading to an evaluation
of pupilometry and whether it could function as a newly proposed test within licenced venues
for validating intoxication observations.
A sizeable amount of the current research that exists surrounding pupilometry in
relation to alcohol has been conducted by Rubin and colleagues. Their research has helped
uncover key differences between alcoholics and non-alcoholics in pupil response. Firstly,
alcoholics who have not consumed alcohol recently show deficient pupil reactivity, with
slower reaction time than non-alcoholics (Rubin et al. 1978). Secondly, alcoholics response
to stress (i.e. light reflex) is attenuated and their pupil recovery is faster, with these effects

28. CURRENT MEASURES OF
INTOXICATION 21
exacerbated if the participant has been drinking recently (Rubin et al. 1980). What makes
these noted differences important is that research suggests that pupillary response is related to
the autonomic nervous system, with pupil dilation and contraction indicative of sympathetic
and parasympathetic outflow (Rubin, 1980). Furthermore, as alcohol causes notable
differences and degeneration in the functioning of a natural response, which is controlled and
maintained by the nervous system, pupilometry could therefore be utilized as a representative
measure of alcohol-induced impairment. Being able to detect a person who is an alcoholic is
also a considerably valuable feature of pupilometry, as it takes into account the effects of
tolerance a heavy drinker may possess, which would otherwise diminish the chances of
making a reliable observation. When considering the parallels between HGN and pupillary
response, such as the shared ability to measure the effect of alcohol consumption upon
occulomotor function, pupilometry appears to be the next logical step in adapting measures
suitable for use in night life environments. This is due to the potential to remove the element
of subjectivity and other confounding variables present in HGN through use of a hand-held
pupilometer device to measure pupil response rather than relying directly on observation. A
hurdle facing this implementation, is that there is little research to support the reliability of
pupil response specific to measuring alcohol-induced impairment. For instance, a study by
Fotiou and colleagues (2000) examined two different methods of pupilometry, finding that
both were reliable and effective means of measuring pupil response to stress. On the other
hand, this study was conducted in clinical settings, only included participants who had not
consumed alcohol, and was not seeking to examine pupil response as a measure of
impairment, making it difficult to generalize the findings obtained. Only one study retrieved
specifically focused on the effectiveness of pupillary response for detecting drug and alcohol
intoxication, however it concluded that the current pupil range they used for determining a
sober participant was most likely too sensitive, and a non-automated pupilometer was used to
measure pupil response, relying more on subjective judgement (Richman, McAndrew,
Decker & Mullaney, 2004). Although pupillary response holds growing potential for being a
useful measure in evaluating alcohol intoxication, there is a need for further validating
research to support this claim.
1.5.3 Alcohol and the Colour-word Stroop Task
The final five studies retrieved related to the use of the colour-word Stroop task as a
measure of alcohol-induced impairment, examining the validity and reliability of both the

29. CURRENT MEASURES OF
INTOXICATION 22
paper and newly developed electronic form. Again, this led to an evaluation of the measure
and its potential use within natural settings.
A key study obtained focused primarily at how the effects of alcohol-induced
impairment translate to the colour-word Stroop task, finding that individuals who had
consumed alcohol made more errors and needed a longer duration to complete the task than a
person who is sober (Gustafson & Kallmen, 1990). A limitation however, is that the amount
of alcohol consumed during testing (BAC of .9 the highest recorded) is not representative of
intoxication levels reached voluntarily in licenced venues, suggesting a direction for future
research. There is evidence of cognitive impairment also carrying over to next day hangover
after acute alcohol consumption, significantly interfering with Stroop performance
(McKinney, Coyle & Verster, 2012). Furthermore, the effect of alcohol over the duration
needed to complete the task was significant for women but not for men, with women
generally taking more time yet remaining unable to compensate for the number of errors. A
study by Curtin & Fairchild (2002) obtained similar results, with alcohol producing the
largest increase in error rate and response time, whilst also examining how impaired
cognitive functioning produces the behavioural impairment observed. Interestingly, alcohol
intoxication was discovered not to interfere with encoding and evaluation of colour
information, and only selectively disrupted colour naming and word reading functions (Curtin
& Fairchild, 2002). Instead, an intoxicated individual’s behaviour appears to become
stimulus-driven rather than being influenced by top-down cognitive processing, meaning that
when faced with an incongruent task (i.e. the Stroop task) they are unable to adapt and
resolve the conflict with usual higher cognition such as existing beliefs and expectations.
These findings carry broad implications, particularly for alcoholics, as there are various
conflicts that often exist within drinking contexts which influence the inability to regulate
alcohol consumption. What makes this measure promising for use in practical settings is its
potential to obtain a more specific and individualised perspective of impairment, as the
outcome is related to the performance of the actual patron. Implementing this task outside of
experimental environments has only recently become practical, with the rise of electronic
variations of the colour-word Stroop Task. These versions have been demonstrated to
function efficiently and maintain high test-retest reliability to the original paper version,
however task performance examined was not related to or impacted by alcohol impairment
(Penner et al. 2012). Furthermore, similar findings of validity and reliability were supported
in a study by Gualtieri and Johnson (2006) however this was conducted in experimental

30. CURRENT MEASURES OF
INTOXICATION 23
settings, the Stroop task was examined as a component of an extensive battery rather than
individually, and this was also not in relation to detecting alcohol-induced impairment.
Therefore, more extensive research surrounding intoxication and the Stroop task is currently
needed.
1.6 Conclusion
The articles retrieved in the present literature review highlight a number of shared
findings and implications associated with intoxication and the current measures used to assess
it within practical settings. Alcohol has been demonstrated to possess a severe affect on
cognitive functioning, which consequently influences drink-driving and aggressive behaviour
observed in and around licened venues. Various studies support that an intoxicated person
cannot rely on their own subjective ratings of drunkenness, as they are likely to sizeably over
or underestimate their BAC level. Furthermore, observer-ratings of intoxication are also
generally inaccurate, making it difficult to conduct RSA. Sobriety testing serves an important
purpose in experimental or law enforcement settings, however still provides an on-going
challenge to effectively implement in licenced venues. Studies suggest that HGN testing
could act as a valadating measure of intoxication, yet it still remains flawed as it is ultimately
a subjective-driven measure. Pupillary response as a measure of alcohol-induced impairment
has growing support from research, as it is an autonomic process which can be objectively
measured. Another newly proposed direction is to examine the performance of intoxicated
individuals in the colour-word Stroop task, which may provide a more refined and specific
perspective of individual impairment. In conclusion, this review demonstrates the critical
need for a validated measure of intoxication which can be utilzed effectively within practical
drinking settings. Current measures used to assess intoxication remain questionable for this
task, hence further research is warranted for examining the validity of newly proposed
measures which may assist in identifying and predicting intoxication and impairment in the
night-time economy.

31. CURRENT MEASURES OF
INTOXICATION 24
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Citek, K., Ball, B., & Rutledge, D. A. (2003). Nystagmus testing in intoxicated individuals.
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Cromer, J. R., Cromer, J. A., Maruff, P., & Snyder, P. J. (2010). Perception of alcohol
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Olson, K. N., Smith, S. W., Kioss, J. S., Ho, J. D., & Apple, F. S. (2013). Relationship
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pupil size standards used by police officers for detecting drug impairment. Optometry,
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34. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 27
Chapter 2
Evaluation of Current and Newly Proposed Measures of Intoxication and Impairment:
Pupillary Response and Colour-word Stroop Task Performance
Stuart Maclachlan
Student ID: 210706466
Supervisor: A/Prof Peter Miller
Associate Supervisor: Nic Droste
Campus: Waterfront, Geelong
Word Count: 4,998
“I, the undersigned, declare that this Empirical Report is less than the specified word limit,
and that it comprises original work and writing by me, and that due acknowledgement has
been made to all other material used.”
Signed: Date: 27 / 10 / 2014

35. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 28
2.1 Abstract
Introduction: Alcohol-related violence and drunk driving continue to present major issues
within Australia. Limited research however currently exists as to improving measures of
detecting intoxication and impairment within licenced venues. The present study aimed to
address this by evaluating the relationships between various measures of alcohol intoxication
and cognitive impairment (both current and newly proposed) at increasing levels of alcohol
consumption.
Methods: 194 participants (103 males (53.1%), and 91 females), aged between 18 and 33
years old (M = 19.49, SD = 1.99) from across various nightclubs in Geelong completed an
initial questionaire, followed by various intoxication and impairment testing (Stroop task,
breathalyser, and pupilometer).
Results: Preliminary bivariate correlations identified strong associations with alcohol
consumption and current measures, while moderate effect sizes were obtained for BAC level
and Stroop task performance, and the majority of pupil functions. A series of paired-sample t-
tests revealed current measures were sensitive to alcohol consumption as BAC increased,
with participants and interviewers rating themselves and others significantly higher on
intoxication at follow up testing. MANCOVA results indicated that whilst controlling for
demographics: (1) participants who had consumed more alcohol scored higher on
self/observer-reported intoxication, and (2) heavily intoxicated participants had significantly
slower pupil constriction speed compared to when sober. Results for Stroop task performance
were not found to be significant.
Conclusions: Current measures used in licenced premises were able to significantly detect
intoxication, however results obtained were generally inconsistent, highlighting the difficulty
in relying on subjective, self or observer accounts of drunkenness. Pupilometry has the
potential to be an accurate and reliable measure for detecting impairment within licenced
venues. Further research is needed however to investigate this finding under controlled
experimental settings, and to explore pupil functions under different conditions by modifying
the parameters of the pupilometer.

36. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 29
Evaluation of Current and Newly Proposed Measures of Intoxication and Impairment:
Pupillary Response and Colour-word Stroop Task Performance
Alcohol is one of the most used and readily available drugs in Australia, being
frequently consumed at levels considered risky or harmful for long term health and well-
being (ABS, 2012). More specifically, alcohol has been demonstrated to impact on a range of
executive functioning, such as judgement of performance, expectancies, attention, and
reaction time (Guillot, Fanning, Bullock & McCloskey, 2010). In the context of nightlife and
licensed venue patrons, this marked impairment of cognitive functioning has been associated
with factors such as driving under the influence (Cromer, Cromer, Maruff & Synder, 2010),
and engaging in aggressive behaviour (Haines & Graham, 2005; Miller, Wells, Hobbs,
Zinkiewicz, Curtis & Graham, 2014). A major barrier facing effective measurement of
intoxication within licenced premises is that breathalysers (the primary tool for sobriety
testing in roadside interventions) are ultimately impractical for adaption to night life settings
due to a number of issues surrounding accurate interpretation. For instance, residual mouth
alcohol is likely to influence false positive readings, and cannot be controlled for without
prolonged cooperation of patrons. Asides from enforcement issues, blood alcohol
concentration (BAC) is susceptible to various unique individual factors such as tolerance and
fatigue, which may further complicate interpretation and consistent application. Therefore, in
order to address these growing concerns there is an underlying need to develop a
standardised, validated measure of intoxication and impairment which can be quickly, and
consistently applied wtihin licenced premises and field applications (Graham et al. 2013).
2.2.2 Current Measures of Intoxication and Impairment
Previous research suggests that the measures commonly used to assess intoxication
and alcohol-induced impairment are either limited, or difficult to apply within night life
settings (Miller et al. 2014). For instance, an individual’s ability to self-monitor their
drunkeness and subsequently infer their cognitive impairment is often unreliable, as this is
influenced by both the amount of alcohol consumed (Grant, LaBrie, Hummer & Lac, 2012),
and whether their BAC is either accending or decending (Gengo, Gabos, Straley & Manning,
1990). For instance, a person at a higher level of intoxication is more likely to underestimate
their BAC by a sizable amount, whilst reporting lesser impairment as they become sober.
However, contrary evidence suggests that impairment to executive functioning (e.g. short-

37. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 30
term memory, judgement etc.) remains relatively stable across a period of drinking, and does
not recover in proportion to BAC (Cromer, Cromer, Maruff & Synder, 2010). This noted
discrepancy between self-report and BAC demonstrates both the unreliability of BAC as an
impairment measure, and self-report alone as an accurate measure of intoxication.
Furthermore, observing intoxication in others is just as likely to be inaccurate due to
the lack of reliable physical signs and symptoms, making it difficult to discriminate between
levels of drunkeness. This is complicated primarily by an individual’s tolerance to alcohol
which may mask physical identifiers of intoxication, and consequently make a person who is
a chronic drinker appear almost sober in comparison to someone with lesser developed
tolerance (Olson, Smith, Kioss, Ho & Apple, 2013). Although there are behaviours
consistently associated with intoxication (e.g. slurred speech, staggered gait etc.) these
patterns do not generally occur until a considerably high BAC is obtained (typically between
.15 and .20) at which point cognitive function is already heavily impaired (Brick &
Carpenter, 2001). The challenge therefore lies in that an overwhelming percentage of
intoxication is not visible, leaving observations to be based on limited subjective signs which
act as poor, unreliable predictors of drunkenness (Perham, Moore, Sheperd & Cusens, 2007).
This has implications for staff at licenced venues who are likely to permit entry or continue
service of highly intoxicated patrons.
Horizontal gaze nystagmus (HGN) is a physiological response which has been
effectively implemented as a standardised field sobriety test (SFST) by law enforcement in
the United States (Citek, Ball & Rutledge, 2003). This method of testing functions as alcohol
effects ocular movement via neural pathways, inhibiting the smooth pursuit system and
ability to maintain gaze, resulting in involuntary jerking movements of the eye (Goding &
Dobie, 1986). HGN testing has proven to be both a reliable and accurate measure of
identifying intoxication within experimental and natural settings, with evidence supporting
that it is able to discriminate impairment from BAC levels as low as .08 (Citek, Ball &
Rutledge, 2003; Dixon, Clark & Tiplady, 2009). The difficulty with adopting HGN testing
within licened venues however, is that it is vulnerable to a multitude of confounding variables
such as the quality of lighting in the venue, and the skills and training of the person
conducting the test (Rubenzer, 2008). Despite these findings, HGN testing importantly
demonstrates the value of further examining occulomotor function as an indicator of alcohol-
related impairment.

38. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 31
2.2.3 Newly Proposed Measures of Intoxication and Impairment
Despite the established link between occulomotor function and intoxication, few
measures have been proposed for predicting alcohol-induced impairment. One method which
has shown potential through previous research is pupilometry, the measurement of pupil
diameter across various conditions. Furthermore, previous studies by Rubin and collegues
have so far identified various differences which exist between alcoholics and non-alcoholics
in terms of pupillary response. Firstly, alcoholics who have not consumed alcohol recently
show deficient pupil reactivity, with slower reaction time than non-alcoholics (Rubin et al.
1978). Secondly, alcoholics responses to stress (i.e. light reflex) are attenuated and their
pupil recovery is faster, with these effects exacerbated if the person has been drinking
recently (Rubin et al. 1980). With the ability to observe the degenerative effect of alcohol
consumption upon occulomotor function, pupilometry appears to be the next logical step in
adapting a measure suitable for use in night life environments for a number of reasons.
Firstly, unlike HGN testing, pupilometry can be conducted in an objective manner through
use of a hand-held device which automatically measures various pupil functions before and
after exposure to light. Furthermore, by using a pupilometer, bar and security staff at venues
would be able to measure patrons quickly and efficiently, alleviating the need for prolonged
cooperation. Before this can be achieved however, there is a need for further research into the
connection between pupillary response and intoxication, specific to measuring within natural
settings.
A limitation of common sobriety testing (such as BAC) is that it can usually only
provide proportional inferences, rather than specific conclusions in terms of impairment
unique to the individual being tested (Brick & Carpenter, 2001). That is, only predictions of
impairment can be made based on what would be expected from an average person at a
particular BAC level. One cognitive task which may prove useful in addressing this issue is
the colour-word Stroop task, which has been used to measure various executive functions
such as concerntration effectiveness, inhibitory control, and mental flexibility. (Penner, et al.
2012). It involves presenting a series of incongruent stimuli (e.g. the name of a colour is
printed in a colour not denoted by the name), causing interferences with reaction time and
number of correct responses. Previous research surrounding intoxication and the Stroop task
is limited, however there is evidence suggesting that individuals who have consumed alcohol
make more errors and need a longer duration to complete the task than those who are sober

39. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 32
(Gustafson & Kallmen, 1990; Curtin & Fairchild, 2002). To date, there are no studies which
have examined how alcohol-induced impairment translates to the colour-word Stroop task
using participants outside of controlled, experimental settings. With the recent adaption of the
Stroop task to electronic form, and evidence of strong test-retest reliability compared to the
original paper version (Penner, et al. 2012), research examining the Stroop effect within
natural environments has only since become feasible. This is due to the reduced time need,
ease of operation, and consistency which the electronic version provides, making it suitable
for use in licenced venues.
2.2.4 Aim and Hypotheses of the Present Study
Currently, there is a gap in existing knowledge surrounding how to best approach
detecting intoxication and impairment within licenced venues. The present study aimed to
address this by evaluating the relationships between various measures of alcohol intoxication
and cognitive impairment (both current and newly proposed) at increasing levels of alcohol
consumption, which was measured by number of standard drinks consumed, and BAC level.
Based on the literature reviewed, the following hypotheses were proposed:
H1: There will be significant differences in measures of self-reported and observer-reported
intoxication as BAC increases.
H2: There will be significant differences across the various pupil functions in response to
light as BAC increases.
H3: There will be a significant difference in performance on the colour-word Stroop task as
BAC increases.
H4: Controlling for age and gender, alcohol consumption will have a significant positive
effect on current measures of intoxication (i.e. self-reported and observer-reported)
H5: Controlling for age and gender, alcohol consumption will have a significant negative
effect on recorded pupil function/s
H6: Controlling for age and gender, alcohol consumption will have a significant negative
effect on colour-word Stroop task performance

40. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 33
2.3 Method
2.3.1 Design and Procedure
An event-level repeated measures survey was used. Ethics approval was obtained
from the Deakin University Human Ethics Advisory Group – Health prior to conducting the
study. Participants were recruited by interviewers across three separate university organised
social events. Permission to attend and conduct the study at each event was obtained by both
the event organisers, and the venue staff. Data collection was divded into two stages; the
initial questionaire, followed by intoxication/impairment testing (Stroop task, breathalyser,
and pupilometer). This process overall took each participant approximately 5 minutes to
complete. Participants were provided a card with contact information, and an ID number so
that they could return for repeat testing after 1-2 hours. An incentive of entry to a lottery for a
cash voucher prize ($100 Westfield card) was offered to encourage participants to return for
post-testing
2.3.2 Materials and Measures
Demographics. Participant age and gender were recorded.
Alcoholic drinks. Participants’ amount of alcohol consumed was measured by the
number of standard drinks they reported to have finished in the last 12 hours. Standard drinks
were assessed using the basic guideline of 0.6 standard drinks for a pot of light beer (2.7%
alc./vol), 1.1 for a pot of full strength beer (4.8% alc./vol), 1 standard drink for a bottle of
pre-mixed spirits (5.0% alc./vol), 1.4 standard drinks for an average glass of wine (12%
alc./vol), and 1 standard drink for a shot of spirits (40% alc./vol) (Australian Drug
Foundation, 2009). Interviewers attempted to standardise this by asking participants about
what size glass or container their drinks were served in.
Energy drinks (ED) and mixed alcohol/energy drinks (AED). Participants were
asked to report on the number of ED’s or AED’s they had consumed in the previous 12 hours.
Self-reported Intoxication (SRI) and observer-reported intoxication (ORI). Both
participants and research assistants were asked to indicate on a scale of 0-10 (where 0 =
sober, and 10 = heavily intoxicated) either how drunk they currently felt, or how drunk they
believed the participant to be at the time of the interview.

41. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 34
Behavioural signs of intoxication. Participants were assessed on a number of
behavioural signs and symptoms commonly experienced at higher levels of intoxication (e.g.,
loss of coordination, slurred speech, spilling drinks, staggering gait, glassy/red eyes, or other
signs). Each instance of one of these behaviours were summed, so that the higher the score,
the higher number of intoxicated behaviour a participant displayed.
Fatigue. Participant’s fatigue was assessed by various questions relating to the
number of hours sleep per average night, whether their sleep patterns had been disturbed
throughout the week and whether they had consumed any coffee in the last 12 hours.
Illicit/other drugs. Participants were asked if they were willing to disclose any use of
illicit or pharmaceutical drugs in the last 12 hours, and if so, specifying which drug they had
taken. Participants were first reminded that they did not have to answer this question, and that
any information provided would be strictly confidential.
Colour-word Stroop task (CWST). Participants performance on the Stroop task was
assessed by examining if they passed (and if so, how long it took to complete), or if they
failed (and if so, how many correct responses they achieved). Participants were allowed a
practice test on their first time to ensure adequate understanding of the task. The number of
correct responses was used as the variable for assessing cognitive impairment, with the lower
the score, the greater the alcohol-induced impairment expected.
BAC. Participants BAC level was assessed using an Anadatech Alcosense Prodigy
breathalyser (error margin ± -0.02) calibrated, and meeting Australian standards. Participants
were required to blow one continuous breath into the mouthpiece for five to ten seconds. To
increase the accuracy of measurement, participants were instructed to wait 10 to 15 minutes
after finishing their last drink, the time expected for residual alcohol to dissipate from the
mouth. To remove bias, interviewers were required to have made their observations of
participant intoxication before learning their BAC level.
For the purpose of analysis, BAC was operationalised into five levels: sober (defined
as 0), slight (defined as 0.001-.05), moderate (defined as .05 - .08), intoxicated (defined as
.08 - .10) and heavily intoxicated (defined as .12 +). Similarly, number of standard drinks was
operationalised into four levels: none (defined as 0), low (defined as 1 – 4) moderate (defined
as 5 – 9), and high (defined as 10+).

42. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 35
Pupillary response. Participant’s pupillary response to light was assessed using a
hand-held pupilometer. The device was held to the participant’s eye, administering a single
flash, throughout which they had to refrain from blinking. The device then automatically
recorded output for a number of pupil functions, which are summarised below:
Table 2.1
Description of Pupil Functions
Function Measures and Purpose
INIT Represent the diameter of the pupil before the
reflex. Recorded in millimeters (mm)
END Represent the diameter of the pupil just at the
peak of the reflex. Recorded in mms.
DELTA Amount of the constriction. Recorded as a
percentage of initial diameter.
LAT Refers to the latency and represents the time
of the onset of the reflex. Recorded in
seconds.
ACV Average constriction velocity. Refers to the
constricting movement of the pupil diameter
responding to the flash of light. Recorded as
millimeters/second
MCV Maximum constriction velocity. Refers to the
constricting movement of the pupil diameter
responding to the flash of light. Recorded as
millimeters/second.
ADV Dilation velocity. Represents the average
pupillary velocity after having reached the
peak of the constriction, the pupil tends to
recover and dilate back to its initial pupil
diameter. Recorded in millimeters/second.
T75 Total time taken by the pupil to recover 75%
of the initial resting pupil size after it reach
the peak of constriction.
The pulse duration (i.e. how long the light flashed for) of the pupilometers used was set to
216ms. The measurement duration (i.e. how long the pupilometer measured the pupil after

43. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 36
the flash) was set to 4 seconds. The pulse strength (i.e. the strength of the light pulse) was set
to 50 microwatts, and the background level (i.e. the amount of background light that the
pupilometer produces before/after the flash) was set to 0 microwatts.
2.3.3 Participants
A convenience sample of Deakin University students were recruited by research
assistants, who attended a number of university organised social events. Participation was
voluntary, and entry into a lottery for a cash voucher prize was offered as an incentive to
return for post-testing.
Initally, 205 participants (54.1% male) completed the survey (90.2% acceptance rate).
After cleaning the data of incomplete cases, 194 participants remained (103 males (53.1%),
and 91 females), Participants were aged between 18 and 33 years old (M = 19.49, SD = 1.99).
An a priori power analysis showed a minimum of 167 participants were required to replicate
an expected moderate effect size (f = 0.148) with 95% statistical power.
2.4 Results
2.4.1 Preliminary Analyses
Data was cleaned in order to meet assumptions of normality. The variable
behavioural signs was not included due to being non-normally distributed, with skewness of
1.92 (SE = .14) and kurtosis of 4.96 (SE = .29). Furthermore, two pupil functions ADV and
T75 were removed due to missing data greater than 5%. This could be potentially explained
by the measurement duration set on the pupilometers not being calibrated long enough to
reliably detect these functions.

44. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 37
Table 2.2
Alcohol Consumption Frequencies of Participants by BAC and Number of Standard Drinks
Variable N %
BAC level
Sober 51 26.3%
Slight 39 20.1%
Moderate 29 14.9%
Intoxicated 37 19.1%
Heavily intoxicated 38 19.6%
Standard drinks
None 37 19.3%
Low 44 22.9%
Moderate 64 33.3%
High 47 24.5%
Pearson correlations between the two alcohol consumption variables, and the
numerous measures of intoxication and impairment were assessed to explore the direction
and strength of bivariate associations (Table 3). Results indicated that BAC was associated
with almost all measures of intoxication/impairment, with only two pupil functions (i.e.
PUPINIT and PUPEND) not being significantly correlated. On the other hand, the number of
standard drinks consumed only correlated significantly with PUPMCV (r = .15, p <.05), self-
reported intoxication (r = .66, p = <.01), and observer-reported intoxication (r = .71, p <.01).
To avoid the risk of multicollinearity between pupil functions PUPACV and PUPMCV (r =
.90, p <.01), PUPACV was removed from exploratory analyses due to having a weaker
association with alcohol consumption.

45. EVALUATING MEASURES OF INTOX/IMPAIRMENT 38
Table 2.3
Bivariate Correlation Matrix of Alcohol Consumption and Measures of Intoxication & Impairment by Single time Point
Variable 1 2 3 4 5 6 7 8 9 10 11
1. PUPINIT
2. PUPEND .88
3. PUPDELTA .51**
.80**
4. PUPLAT .16**
.27**
.36**
5. PUPACV .13*
.42**
.70**
.37**
6. PUPMCV .09 .40**
.72**
.30**
.90**
7. SRI -.04 .02 .10 .19**
.07 .11
8. ORI -.13*
-.08 .02 .05 .11 .14*
.74**
9. BAC .00 .09 .22**
.20**
.25**
.29**
.70**
.75**
10. Std. Drinks .00 .04 .08 .06 .11 .15*
.66**
.71**
.70**
11. CWST -.02 -.09 -.12 .05 -.05 -.04 -.10 -.13*
-.16**
-.11
Note. *
p <.05, two-tailed. **
p <.001. two-tailed.

46. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 39
2.4.2 Influence of Alcohol Consumption over time
A series of paired-samples t-tests were conducted to determine which measures of
intoxication and impairment were sensitive to alcohol consumption as BAC increased.
Results indicated that BAC readings increased on average by .05 across initial and follow up
testing (Table 4). Participants on average waited just under 2 hours (M = 1.85, SD = 1.42)
before returning for post-testing. A significant difference was obtained in the scores across
pre-post testing for SRI, with participants rating themselves on average 2.70 higher on
intoxication during post-testing. Similar results were obtained for ORI, with interviewers
rating participants on average 2.46 higher on intoxication at post-testing, overall supporting
the assumptions of H1. However, no other measures of impairment (including all recorded
pupil functions and performance on CWST) were found to have a significant difference
across pre-post testing, with minimal variance recorded between testing. Subsequently, H2
and H3 were only partially supported by the previous bivariate correlation findings.
Table 2.4
Descriptive Statistics and t-test Results for Measures of Intox/Impairment and BAC over Pre-
post Testing
Pretest Posttest 95% CI for Mean
DifferenceOutcome M SD M SD n r t df
PUPINIT 6.92 .75 6.80 .68 54 -0.01, 0.25 .76 1.80 53
PUPEND 5.15 .81 5.08 .80 54 -0.07, 0.20 .79 .92 53
PUPDELTA -24.85 5.31 -25.26 6.01 54 -0.61, 1.42 .78 .79 53
PUPLAT .22 .02 .23 .02 54 -0.01, 0.00 .17 -1.09 53
PUPMCV -4.94 .89 -4.92 1.03 54 -0.21, 0.17 .73 -.20 53
SRI 2.48 2.60 5.19 2.45 54 -3.59, -1.81 .16 -6.09**
53
ORI 2.35 2.50 4.81 2.36 54 -3.31, -1.60 .17 -5.77**
53
CWST 8.27 2.63 7.96 2.69 54 -0.57, 1.20 .25 .71 53
BAC 0.04 0.04 0.09 0.08 54 -0.07, -0.02 .16 -4.43 53
Note. *
p <.05, two-tailed. **
p <.001. two-tailed
2.4.3 Effects of Alcohol Consumption on Measures of Intoxication & Impairment

47. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 40
Two separate exploratory one-way MANCOVA’s were performed to examine the
effects of alcohol consumption (while controlling for age and gender differences) on current,
and newly proposed measures of intoxication and impairment. Levene’s tests on SRI and
ORI, were both found to be significant across the analyses conducted (p <.01). However,
there is evidence to suggest univariate analyses are robust to violations of Levene’s test,
particularly if group sizes are relatively equal (Field, 2013) which is true of this sample (refer
to Table 2). As Box’s M was found to be violated for both analyses, Phillai’s trace was used
for interpretation due to being considered the most robust of the four statistics.
A MANCOVA was conducted where BAC acted as the fixed factor. Due to PUPINIT
and PUPEND being determined as not significantly associated with BAC (refer to Table 3),
they were excluded from the analysis. Findings revealed a significant multivariate main effect
of BAC on intoxication and impairment measures, F (24, 648) = 6.47; p <.001; Pillai’s trace
= .74, ηp
2
= .194. Univariate analyses (Table 5) showed a large, significant main effect of
BAC on SRI, with heavily intoxicated participants (.12+) rating themselves on average 2.7
higher compared to someone only slightly intoxicated (0.001-.05) A large, significant main
effect of BAC on ORI was also found, with interviewers rating heavily intoxicated
participants on average 3.67 higher than someone only slightly intoxicated. Finally, a
moderate, significant main effect of BAC on PUPMCV was found, with heavily intoxicated
participant’s pupil constriction in response to light being approximately 1mm per second
slower compared to someone sober. No significant effect of BAC towards PUPLAT,
PUPDELTA or number of correct CWST responses was found.
For the second MANCOVA, number of standard drinks consumed acted as the fixed
factor. Only SRI, ORI, and PUPMCV were included as DV’s, being the only measures
determined significantly sensitive to the IV (refer to Table 3), hence H6 was not supported.
Findings revealed a significant multivariate main effect of number of standard drinks
consumed on intoxication and impairment measures, F (18, 474) = 7.36; p = <.001; Pillai’s
trace = .65, ηp
2
= .219. Furthermore, significant univariate main effects were obtained for
SRI, F (3, 462) = 63.87; p <.001; ηp
2
= .543; and ORI, F (3, 616) = 47.64; p = .001; ηp
2
=
.470. Pairwise differences in SRI between low (M = 2.55) and high (M = 5.73) consumption,
and ORI between low (M = 2.39) and high (M = 5.81) consumption, revealed significantly
higher ratings of intoxication on average as number of standard drinks consumed increased
(satisfying H4). Finally, no main effect of number of standard drinks on PUPMCV was
found, meaning H5 was only partially satisfied.

48. EVALUATING MEASURES OF INTOX/IMPAIRMENT 41
Table 2.5
Univariate Analysis of Variance for Current/Newly Proposed Measures of Intoxication & Impairment by BAC
Note. Bonferroni adjusted alpha levels were used for significance testing, with BAC difference significant where b = p < .008.
Dependent
Variable
F df df
error
P η2
partial Sober Slight Moderate Intoxicated Heavy intox.
M(SD) 95%CI M(SD) 95%CI M(SD) 95%CI M(SD) 95%CI M(SD) 95%CI
Current measures
SRI 47.97 4 479 .000b
.028 .73(.28) [.17,
1.28]
3.07(.28) [2.52,
3.62]
4.75(.32) [4.10,
5.40]
5.44(.31) [4.82,
6.06]
5.77(.29) [5.19,
6.35]
ORI 51.57 4 164 .000b
.557 .47(.29) [-.10,
1.05]
2.69(.29) [2.11,
3.27]
4.03(.34) [3.35,
4.71]
4.99(.32) [4.34,
5.64]
6.36(.30) [5.76,
6.97]
Newly proposed measures
PUPMCV 6.55 4 164 .000b
.138 -5.11(.14) [-5.40,
-4.83]
-5.46(.14) [-5.75,
-5.18]
-5.24(.16) [-5.57,
-4.91]
-4.74(.16) [-5.06,
-4.43]
-4.48(.16) [-4.78,
-4.19]
PUPLAT 1.68 4 164 .15 .039 .22(.00) [.21,
.23]
.22(.00) [.22,
.23]
.22(.00) [.21,
.23]
.23(.00) [.22,
.24]
.23(.00) [.22,
.24]
PUPDELTA 2.67 4 164 .03 .061 -25.10(.90) [-26.89,
-23.32]
-26.71(.90) [-28.50,
-24.93]
-26.10(1.06) [-28.20,
-24.93]
-23.96(1.01) [-25.95,
-21.96]
-22.79(.94) [-24.66,
-20.93]
CWST 1.20 4 164 .31 .539 8.35(.46) [7.43,
9.27]
8.23(.46) [7.32,
9.15]
7.77(.54) [6.63,
8.78]
7.44(.51) [6.41,
8.46]
7.04(.48) [6.08,
7.99]

49. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 42
2.5 Discussion
The purpose of this study was to evaluate the relationships between various
measures of alcohol intoxication and cognitive impairment at increasing levels of alcohol
consumption, which was operationalised by both BAC level, and number of standard
drinks consumed. The study aimed to address the issues surrounding intoxication
measurement within licenced venues in two ways: by critically examining the
effectiveness of measures currently relied upon (e.g. SRI and ORI), and by exploring
newly proposed measures supported by previous literature (e.g. pupillary response and
CWST performance).
Differences in SRI, and ORI were significant as BAC increased, suggesting both
measures were sensitive to alcohol consumption, and supporting H1. On average,
participants and interviewers rated themselves and others significantly more intoxicated as
the night progressed, supported by previous research (Gengo, Gabos, Straley & Manning,
1990). There was however no significant difference between any of the pupillary response
measures, as well as performance on the CWST, hence H2 and H3 were only partially
supported by bivariate correlational findings. Furthermore, BAC and number of standard
drinks consumed both had significant associations with various intoxication and
impairment measures, including SRI, ORI, and PUPMCV. Intoxicated participants rated
themselves higher than someone only slightly drunk, whilst interviewers rated intoxicated
participants in an identical manner, supporting H4. Interestingly, participants considered
heavily intoxicated (.12+) only reported themselves on average as 6 out of 10, suggesting
the difficulty in accurate self-rating intoxication, and supporting past research (Grant,
LaBrie, Hummer and Lac, 2012; Bellis, Hughes, Quigg, Morleo and Lisboa, 2010).
Similarly, interviewers on average rated heavily intoxicated participants even less (5 out of
10), which is inconsistent with research suggesting that obvious physical signs of
intoxication occurring within these BAC ranges (e.g. slurred speech) tend to assist in
assessment of intoxication (Perham et al. 2007). This finding has implications in terms of
patron service in licenced venues, suggesting staff are more likely to continue service to
someone already intoxicated. BAC had a moderate effect on PUPMCV (explaining 13% of
the variance), with heavily intoxicated participant’s pupil constriction in response to light
being significantly slower, compared to someone sober. This finding builds upon past
research by Rubin et al. (1978) and Rubin, (1980), which significantly linked alcohol
consumption amongst participants with slower pupil reflex to light. Furthermore, no

50. EVALUATING MEASURES OF
INTOX/IMPAIRMENT 43
significant effect of number of standard drinks on PUPMCV was found, meaning H5 was
only partially satisfied. Finally, there was no significant effect of alcohol consumption
(both BAC and number of standard drinks) on CWST performance, meaning therefore H6
was not supported.
2.5.1 Number of Standard Drinks as a Predictor of Alcohol Consumption
Despite categorising number of standard drinks based on levels suggested by
previous research (Graham et al. 2013), it correlated with fewer measures of intoxication
and impairment than BAC, and was found to only be associated with SRI and ORI.
Difficulty in applying number of standard drinks as a predictor of alcohol consumption
could be attributed to a number of reasons present in the procedure of the study. For
instance, standard drinks was assessed based on a time frame of the previous twelve hours,
meaning it is possible for a participant to have a substantial gap since their last drink. The
underlying problem is that number of drinks consumed is not necessarily indicative of how
intoxicated or impaired a person is. Another explanation for the discrepancy is that
standard drinks is dependent on the participant providing the information, rather than
being objectively measured, meaning there is greater potential for bias or error (Rubenzer,
2008). For example, more intoxicated participants are more likely to exaggerate the
amount they had consumed, or have difficulty recalling due to impaired executive
functioning (Guillot, Fanning, Bullock & McCloskey, 2010). Another challenge related to
accurately converting the quantity of alcohol reportably consumed by the participant to
standard drinks (e.g. whether it was light/heavy beer, pot or pint, etc.). Although this
conversion was performed by the interviewer in an attempt to increase the reliability of the
measure, it is still vulnerable to self-report biases.
2.5.2 Influence of Alcohol Consumption over time
Of all reported differences as BAC increased for the various measures of
intoxication and impairment, only those observed for SRI and ORI were found significant.
An explanation as to why many of these measures were not sensitive to alcohol over time
may be due to a range of confounding variables present in the environment which could
not be controlled. For example, fatigue effects are likely to have been present between
testing which in turn would have influenced pupillary behaviour (Rubenzer, 2008).
Furthermore, polydrug use was also an issue, with a number of participants reporting use
of illicit substances likely to alter pupil function during testing (Goding & Dobie, 1986). A

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different explanation relates to the relatively short duration observed between testing, with
some participants returning far closer to their original testing than others. Similarly, BAC
increases observed between testing were also relatively low, with a number of participants
actually sobering up across time rather than getting more intoxicated. These findings
suggest the need to perform testing at high intoxication levels within a controlled,
experimental design.
2.5.3 Alcohol Consumption on Pupillary Response
Interpreting the influence of alcohol consumption on pupillary response is less
clear, due to the exploratory nature of this investigation. Two pupil functions which acted
in accordance with previous research were PUPINIT and PUPMCV, with no significant
difference found between sober and intoxicated participants in terms of the diameter of the
pupil prior to the reflex (Rubin et al. 1980), but a significant difference in the maximum
constricting movement prior to the flash (Rubin et al. 1978). Although correlational
analyses suggested significant relationships between BAC and various other pupil
functions (e.g. PUPLAT, PUPDELTA), these effects were not significant when the
analyses were run. This is inconsistent with previous research by Fotiou et al. (2000),
which suggested pupil latency and constriction as useful measures for identifying
alcoholism. However, it is important to note that the study by Fotiou and colleagues was
conducted in a laboratory setting, utilised dynamic pupilometry, and was assessing chronic
alcoholism rather than acute alcohol intoxication. Another explanation is that it still
remains relatively unclear as to what particular level of intoxication is required before
certain pupil functions become noticeably impaired due to alcohol. It could perhaps be that
functions such as PUPLAT or PUPDELTA do not become sensitive to alcohol until
substantially high levels of intoxication, beyond what is generally replicated within
experimental settings. This was demonstrated particularly for PUPMCV, which fluctuated
around the same level until a participant reached the top two BAC stages (.08+). Finally,
pupil functions ADV and T75 were both excluded from analyses due to missing data,
which was potentially attributed to a setting on the pupilometer. This presents a correction
for future research, by modifying the measurement duration to determine if these functions
can be better detected with longer recording of pupil recovery, or whether this type of
measurement is useful at detecting low levels of intoxication.
2.5.4 Stroop task Performance as a Measure of Alcohol-induced Impairment

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Performance on the CWST was proposed as an exploratory method of gaining a
more specific understanding of a participant’s impairment. Despite a weak correlational
analysis suggesting a relationship between BAC and number of correct CWST responses,
no significant effect was observed either directly, or over time. Again, it is difficult to
interpret as to why CWST performance was not sufficiently sensitive to alcohol
consumption due to the relatively new direction of this study. This is particularly true
considering that what few previous studies exist surrounding CWST at various levels of
intoxication, all suggested that number of correct responses should significantly decrease
over testing (Curtin and Fairchild (2002; Gustafson and Kallmen, 1990). A possible
explanation as to the inconsistency lies in the differences of test procedures. For instance,
the study by Gustafson and Kallmen (1990) was conducted in clinical settings, at
considerably lower levels of intoxication not reflective of alcohol use in night life settings
(.09 was highest BAC recorded). Furthermore, the length of the CWST used across these
studies was substantially longer (up to 300 words), suggesting that perhaps the length of
the CWST used for the present study was not long enough to detect a significant effect.
However, this duration of testing is certainly unfeasible in a nightlife context. Time taken
to complete is another indicator of Stroop task performance which although was recorded,
it was not used in analyses due to being more difficult to clearly interpret impairment (for
instance, a sober person who believes performance is measured solely on correct
responses, may actively choose to take their time in responding). Finally, there is a
potential for a practice effect, as participants were repeating this task across relatively
short duration.
2.5.5 Implications and Future Research
The outcomes of this study provided a broad range of implications. Firstly,
although current measures used in licenced premises were able to significantly detect
intoxication, results obtained were generally inconsistent (i.e. heavily intoxicated patrons
rating themselves only as a 6 out of 10 on a scale of drunkenness), and supported the vast
previous research highlighting the difficulty in relying on subjective, self or observer
accounts of drunkenness. Secondly, BAC was observed to be a far superior predictor of
alcohol impairment than number of standard drinks consumed, suggesting that further
investigation into measures which relate to BAC will assist in the validation of an
intoxication measure for night life settings. Thirdly, one possible measure for this role is
pupillary response, with findings supporting a significant difference in participant’s

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maximum constricting movement of their pupil in response to light (PUPMCV) across
increasing intoxication. This result warrants further exploration into pupillary functioning
as a measure of impairment in licenced venues, particularly to expand the research
surrounding monocular pupilometer devices, and strengthen the understanding of pupil
functioning in intoxicated patrons. Fourthly, although performance on the CWST was not
sensitive to alcohol-induced impairment within the parameters of this study, further
research would benefit in addressing particular issues such as appropriate length of testing
for detecting alcohol-induced impairment. Finally, there are a number of potential future
directions identified from this study, such as performing within a controlled environment
at high intoxication levels reflective of night life settings, and modifying the pupilometer
to better examine missing functions ADV and T75. Overall, pupilometry has the potential
to be an accurate and reliable measure for detecting impairment within licenced settings.

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