The branch of psychological science that study relationship between psychological phenomenon and physical properties of a stimulus.

1. Problems of Psychophysics
Dr Rajesh Verma
Assistant Professor in Psychology
Govt. College Adampur, Hisar (Haryana)

2. Meaning
The word Psychophysics is made up of Psychology
+ Physics.
Psychology = Psychological variables (Specially
Sensation and Perception) of an individual.
Physics = Physical Properties of Stimulus.
Means studying the
relationship between
psychological phenomenon
and physical properties of
stimulus.

3. Definition
The branch of psychological science that study
relationship between psychological phenomenon and physical
properties of a stimulus.
The relationship between stimuli and the
sensations they evoke has been studied
in a discipline, called psychophysics
(NCERT, XI).
“The analysis of perceptual processes by
studying the effect on a subject's experience
or behaviour of systematically varying the
properties of a stimulus along one or more
physical dimensions” (Bruce et. Al 1996
quoted by Wikipedia).

4. Problems of Psychophysics
(i) Quantification of Psychic State – Psychic state is
qualitative and subjective variable that needs to
converted into a quantitative variable for testing. It is
achieved through the expression of sum total of
characteristics of a variable in objective form.
(ii) Measurement
of Psychic State –
Assessment of a
variable for its
magnitude as well
as intensity.

5. (iii) Scaling – Determining the location of an object on
a scale or continuum means to allot a numerical value.
These are helpful in establishing cause-effect
relationships between variables.
(iv) Determination of functional relationships and
their mathematical expression – Because mathematical
expressions or models are helpful in estimating the
quantitative behaviour of any system. They help to
explain known
physical
phenomena and
are helpful in
predicting their
behaviour in
time.

6. (v) Manipulation of Psychological Variables –
Quantitative change in the magnitude or intensity of a
variable in order to have pure outcomes i.e. external
interference free inferences.
(vi) Objective Measurement of Magnitude of Sensation –
Strength of sensory experience. Fechner’s law (1860) states
that the intensity of sensation (perception) is proportional to
the logarithm of the intensity of stimulation, therefore the
stimuli that are more
relevant in intensity,
quality, rarity, etc.
will be best received
by individuals and
produce fewer
errors (Liutsko &
Ral, 2014).

7. (vii) Measurement of Sense Experience – Assessment
of their level.
(viii) Minimizing Human
errors which are of three
types i.e.
(a) Errors in perception,
(b) Errors in decision and
(c) Errors in sensation.
(x) Observational Errors.

8. References:
1. NCERT, XI Psychology Text book.
2. Bruce. V., Green, P. R. & Georgeson, M. A. (1996). Visual
perception (3rd ed.). Psychology Press.
3. Ral, J. M. T. & Liutsko, L. (2014). Human errors: Their
psychophysical bases and the Proprioceptive Diagnosis of
Temperament and Character (DP-TC) as a tool for measuring.
Psychology in Russia: State of the Art 7(2), 48-63.

9. Next Discussion
Classical Methods of Psychophysics

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