Spatial clustering and its effect on perceived clustering, numerosity, and dispersion.

Area of Science:

• Cognitive Psychology
• Computational Neuroscience
• Visual Perception

Background:

• Human observers can estimate the numerosity of visual elements.
• The occupancy model explains perceived numerosity based on overlapping regions of influence and item proximity.
• Spatial properties beyond simple counts, like element grouping, can affect perceived numerosity.

Purpose of the Study:

• To investigate how spatial configuration influences perceived numerosity.
• To explore alternative spatial properties (e.g., convex hull area, occupancy area, connectivity, clustering) affecting numerosity perception.
• To determine if perceived dispersion and clustering rely on the same spatial information as numerosity.

Main Methods:

• Participants compared visual patterns with a fixed number of elements (22-40) to judge perceived numerosity.
• Observers also performed separate tasks to judge pattern dispersion and clustering.
• Various spatial indices were quantified, including convex hull area, occupancy area, connectivity, and local clustering, with neighbor radius varied for most indices.

Main Results:

• Perceived numerosity, dispersion, and clustering appear to be based on distinct spatial information.
• Clustering of elements consistently led to a decrease in perceived numerosity.
• Alternative methods for quantifying clustering were explored, each with different properties.

Conclusions:

• Spatial configuration significantly impacts perceived numerosity, independent of the actual element count.
• Clustering is a key spatial factor that reduces perceived numerosity.
• Understanding these spatial influences is crucial for models of visual perception and quantity estimation.