This study examined auditory and visual perception of gap size at both the microscale (specific body parts) and macroscale (full body) levels. Participants judged whether their head, hand, foot, shoulders, or stance width could fit through gaps of varying sizes presented either visually or auditorily. Results found participants accurately judged gap size across conditions with some differences in critical values between microscale body parts and between modalities. Visual judgments showed similar performance for microscale and macroscale, while auditory microscale judgments differed more from macroscale, indicating modality and scale affect affordance perception.

1. AUDITORY VERSUS VISUAL PERCEPTION OF GAP SIZE ON A MICROSCALE
AND MACROSCALE LEVEL
SKYLER GENTRY
DEPARTMENT OF PSYCHOLOGY
WASHBURN UNIVERSITY
Affordances (Gibson, 1979/1986):
• “What the it [environment] offers the individual, what it provides or furnishes, either
for good or ill.”
•All the possible (suffix “-able”) actions that can be done with an object or piece of an
environment.
•Kickable
•Hitable
•Stand on-able
•Gibson proposed the idea of affordances to contrast the idea of Euclidean judgments
of the furniture of the earth.
Visual Affordance Judgments
Warren and Whang (1987)
• Gap passibility
• Yes or no task
• Can you walk through this gap assuming walking at a comfortable
pace without rotating or pivoting your body?
• Πc = 1.16 (shoulder width)
• “Πc” reflects the perceptual boundary separating affording from
nonaffording.
Carello et el. (1989)
• Reachability
• Yes or no task
• Can you grab this target assuming only maximal arm extension?
• Can you grab this target assuming maximal arm extension plus
bending forward at the hips.
• 16 R df, yet affordance judgments highly commensurate with actual reachability.
Warren (1984)
• Stair Climbability
• Yes or no task
• Can you step onto this surface in a normal way without using your
hands or knees?
• Πc = .88 (leg length)
Auditory Affordance Judgments
Russell and Turvey (1999)
• Gap passability
• “Can you walk between a duck and a wall with your eyes closed?”
• Same task and instructions as Warren & Whang (1987)
• Πc = 1.11
Rosenblum, Wuestefeld, and Anderson (1996)
• Reachability
• Yes or no task
• Can you grab this target assuming only maximal arm extension?
• Can you grab this target assuming maximal arm extension plus
bending forward at the hips.
• Πc = .92 (arm length)
PRESENT STUDY
Previous studies have focused purely on affordance judgments in terms of the full body, the
macroscale level. In contrast, the present study focused on affordance judgments in relation
to a portion of the body, the microscale level versus judgments in relation to the full body
appendage, the macroscale level.
• All participants had the gap fitable task for each of the 3 body parts
• Head
• Foot
• Hand
• Shoulder width
• Stance width
METHOD
Participants.
• Undergraduates
• Self-reported normal, unaided hearing.
Materials.
Sound:
• 770 Hz square wave pure tones, 330 msec in duration
• 3 notes, separated by 660 msec of silence
• Broadcast in echoic setting using iPad
Procedure.
• Participants randomly assigned to head, foot, and head condition.
•Between-subjects variable
•Task:
•Participants completed 48 trials for one of the three conditions.
• Affordance task: “yes” or “no” could they fit the desired body part between
two loudspeakers.
•Modality a within-subjects variable
•Auditory (Half of the trials)
•Visual (Half of the trials)
• Gap sizes is a within-subject variable
•Head: 8 - 58 cm with 10 cm increments
•Hand: 4 - 24 cm with 4 cm increments
•Foot: 5 - 35 cm with 6 cm increments
•Shoulder Width: 20 – 70 cm with 10 cm increments
•Stance Width: 20 – 70 cm with 10 cm increments
RESULTS
% “Yes” Judgments
Head: Modality, n.s. Gap size, p = .0001
Modality*Gap size, n.s.
Shoulders: Modality, n.s. Gap size, p=
.0001
Modality*Gap size, p=.0229
Hand: Modality, n.s. Gap size, p = .0001
Modality*Gap size, n.s.
Stance: Modality, n.s. Gap size, p=
.0001
Modailty*Gap size, p=.0351
Foot: Modality, n.s. Gap size, p = .0001
Modality*Gap size, p = .0462
Critical pi values
Modality, p= 0590 Body part, p = .0216
Modality*Body part, p = .0119
DISCUSSION
• Can participants perceive gap size?
• Does modality matters?
•No with the exception of the foot.
• Does microscale matter?
•% “yes”: No
•Critical pi values: Yes
• How do microscale judgments compare to macroscale judgments?
•With vision, about the same
•With audition, notably different
• Implications
• Participants can perform the task with a high degree of accuracy, but
microscale & modality have an influence
• Macroscale vs. Microscale
• No significant difference
Head Shoulder Hand Foot Stance
0.0
0.5
1.0
1.5
2.0
1.361
1.015
0.951
1.113
0.976
Body Part
CriticalPiValue
Head Shoulder Hand Foot Stance
0.0
0.5
1.0
1.5
2.0
1.16
1.028
1.084
0.988
0.873
1.562
1.002
0.819
1.238
1.078
Vision
Audition
Body Part
CriticalPiValue
20 30 40 50 60 70 80
0
20
40
60
80
100
Vision
Audition
Gap Size (cm)
%“Yes”
20 30 40 50 60 70 80
0
20
40
60
80
100
Vision
Audition
Gap Size (cm)
%“Yes”