Computation of mean size is based on perceived size

Area of Science:

• Visual perception
• Cognitive psychology
• Computational neuroscience

Background:

• Understanding how the brain processes visual information is crucial for cognitive science.
• The Ebbinghaus illusion is a well-known phenomenon that alters the perceived size of objects based on surrounding context.

Purpose of the Study:

• To determine if the computation of mean object size relies on perceived or physical dimensions.
• To investigate the role of the Ebbinghaus illusion in the averaging of visual size information.

Main Methods:

• Utilized the Ebbinghaus illusion to create discrepancies between perceived and physical circle sizes.
• Presented four Ebbinghaus configurations simultaneously or sequentially to each visual field.
• Instructed participants to focus solely on the central circles for size judgments.

Main Results:

• Judgments of the mean central circle size were significantly influenced by the Ebbinghaus illusion.
• The illusion affected the coding of individual circle sizes, not the averaging process itself.
• Evidence suggests perceived size, not physical size, is used in computing mean size.

Conclusions:

• The brain uses perceived size, not physical size, when calculating the average size of objects.
• This finding has implications for understanding visual perception and cognitive averaging mechanisms.