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REFERENCES
[1] Wagemans, J.(2016). Perceptual Organization. In J.T. Wixted (series Ed) & J. serences (vol. Ed), The Stevens' Handbook of
Experimental Psychology and Cognitive Neuroscience: Vol. 2. Sensation, Perception & Attention. Hoboken, NJ: John Willey & Sons, Inc.
[2]
Van Den Berg, M. C. J. (2006). * Grouping by proximity and grouping by good continuation in the perceptual organization of random dot
patterns. University of Virginia.
[3] Kubovy, M., Holcombe, A. O., & Wagemans, J. (1998). On the lawfulness of grouping by proximity. Cognitive psychology, 35(1), 71-98.
[4] Sarami, A., & Afhami, R. (2019, April). Induced Perceptual Organization in Ordered Dot-Lattices: The Effect of an Inclined Line. In
PERCEPTION (Vol. 48,pp.126-126). ENGLAND: SAGE PUBLICATIONS LTD.
[5] Sarami, A, & Afhami,R. (2017). Visual Perception of a Lattice of Dots Surrounded by a Tilted Frame: A Gestalt Approach. Visual
science of Art conference (VSAC 2017), 25-27.08.2017. Berlin
Arefe Sarami1, Johan Wagemans2, Reza Afhami1
1Department of Art, Tarbiat Modares University, Tehran, Iran; 2University of Leuven (KU Leuven), Leuven, Belgium
Proximity-induced perceptual grouping of random
dot patterns in the presence of a tilting frame
Introduction
Subject and Method
Random dot patterns and grouping task
Results
Perceptual organization consists of a variety of processes involved in
establishing organized percepts from disjoint elements [1]. such as
perceptual grouping and figure-ground organization. Perceptual
grouping itself also consists of several different processes, like
clustering, segregating, linking, layering, and configuring. Here we
study perceptual grouping of dot patterns, often used to establish
grouping principles such as proximity [1-3, 5].
Our study asks participants to explicitly mark dots that are
perceived to be grouped. We focus on the consistency within and
between observers in the presence of a variable frame around the
dot patterns, asking whether the combination of adot pattern and
the frame could generate an integrated shape [4].
Random dot patterns
Grouping task
The positions of each
dot, (X,Y) coordinates,
are random realizations
of Gaussian
distributions.
(Dot size = 0.02* Frame
size)
Afhami’s Lab of Visual
Perception and Art
- Clicking task
- The assignments of dots to groups was not
restricted to a single group per dot.
Results
Subjects: Ten graduate art students (6 female, 4 male, Age =
27.2±4.8 years, range = 21-36 years).
Stimuli: Ten random patterns of nine dots were generated. For
each pattern, a rectangular frame was tilted at 7 angles around the
dots. For each of these 70 stimuli, ten observers indicated the
groups of dots, and each observer completed four blocks of the
same stimuli, in a different random order.
Task:
- Participants could assign dots to groups by clicking on them (a) and (b).
- When a single group was generated and saved (c), a copy of the stimulus, which
indicated the grouped dots, was displayed alongside of the screen.
- When all dots were assigned to groups (d), the “Next”button lead participants
to the next trial (e).
Analysis and Statistics:
The experiment resulted in 28 grouping reports per dot pattern per
observer. We randomly split the reports in two report sets and
within each report set, we calculated the frequencies with which
each dot-pair was placed in the same group. Correlation
independence tests between frequencies from the two sets of
reports were used to measure the within-subject consistency of
grouping. For all the 28 reports and for each pattern, we also
calculated the correlation independence tests between frequencies
from each participant to those from other participants.
Independence tests between frequencies from each participant and
those from other participants were used to measure the between-
subject consistency of grouping.
For all 70 stimuli
Conclusion
Median
Mean
SEM
SD
Figure1. Within-subject consistency. Twenty-eight grouping repotrs were randomly split
in two report sets. For each dot pattern within each set, the frequency with which each dot-
pair has been placed in the same group was calculated. Figure1 indicates the correlation
between the obtained integrated frequencies in the two sets (Pearson’s r > 0.9, p < 0.05).
Figure 2. Effect of the rotation angle on the grouping done by all participants. All mean
correlation coefficients are greater than 0.9 and correlations are all significant (p< 0.05).
Figure 3. Between-subject consistency. For each participant, the correlation between
the obtained frequencies was calculated against other participants.
Participants were highly consistent in reporting the dots they
perceived as belonging to the same group.
Regardless of the angle of orientation, high between- and within-
subject consistencies show that grouping by proximity remained
unaffected by the tilt of a frame around the patterns.
In an ongoing study, we are investigating the effect of point density
on the above results by repeating the experiments with patterns of
18 dots.
The application used to perform the groupings was
developed in MATLAB GUI 2018.
