The Perceptual
Organization of Point
Constellations
ANSHUL VARMA
[email protected]
Paper Details
 Dry, M., Navarro, D., Preiss, K., and Lee, M. (2009). “The
Perceptual Organization of Point Constellations.” COGSCI
2009: The annual meeting of the Cognitive Science Society.
Clustering Constellation (or constellation like)
 We will be looking how humans cluster constellation or
constellation like points.
 What patterns humans tend to make?
 Are these clustering generally valid?
Researchers From The Gestalt School
 Koffka, 1935; Köhler, 1929; Wertheimer, 1938
 Visual stimuli is dictated by some simple principles:
◦ Relative proximity
◦ Similarity
◦ Good continuation
◦ Common fate
Principle #1: Relative Proximity
 Elements with greater relative proximity are grouped
together.
Principle #1: Relative Proximity Example
Principle #1: Relative Proximity Example
Principle #2: Similarity
 Elements that are similar are perceived to be more related
than things that are dissimilar.
Principle #2: Similarity Example
Principle #2: Similarity Example
Principle #2: Similarity Example
Principle #3: Good Continuation
 Elements arranged on a line or a curve are perceived to be
more related than elements that are not.
Principle #3: Good Continuation Example
Scores
Scores
4.5
4.5
4
4
3.5
3.5
3
3
2.5
2.5
2
2
1.5
1.5
1
1
0.5
0.5
0
0
GPA
Alice
Bob
Mike
GPA
Dan
Mike
Alice
Dan
Bob
Principle #4: Common Fate
 Elements that tend to move in same direction are more
related then elements that are stationary or that move in
different directions.
Principle #4: Common Fate Example
 Driving a car.
Research Aims
 First, testing if Gestalt principles hold in general for
majority of people when they perceive constellation or
constellation like point clustering.
 Second, what structures do we get when we perform
clustering on constellation or constellation like points?
Constellation: Scorpio
Experiment Method
 Participants: 12 observers.
 Stimuli: 30 constellations.
◦ Taken from RS3 (Redshift 3 Desktop Planetarium).
◦ Criteria > 8 stars.
◦ Flipped across horizontal access.
 Procedure: Connect points at free will using a PC.
Clustering Constellation Like Points
Clustering Constellation Like Points
Clustering Constellation Like Points
Experiment
Experiment
Spanning Tree & Minimum Spanning Tree
 A spanning tree is a structure that connects all of the
points in a set with n-1 edges and contains no circuits.
 The minimum spanning tree is the structure that
minimizes the total length of the edges connecting points
(Zahn, 1971).
Results
 First, more than 90% of the people perceive constellation
like structures similarly.
 Second, people seem to form minimum spanning tree like
structure while they clustering constellation like points.
Single Linkage Clustering
 It looks like humans tend to do single linkage clustering
when they are merging constellation or constellation like
points.
Single Linkage: Probably not in general!