Substitution and pooling in crowding.

Area of Science:

• Visual perception
• Cognitive psychology

Background:

• Crowding is a phenomenon that impairs object recognition in peripheral vision.
• The severity of crowding increases with object similarity.
• Flanker reports during crowding have been interpreted as evidence of target substitution.

Purpose of the Study:

• To investigate the mechanisms underlying object recognition breakdown in crowding.
• To differentiate between substitution and pooling models of crowding.
• To determine the contribution of pooling to crowding errors.

Main Methods:

• Presenting observers with a target letter flanked by one similar and one dissimilar letter.
• Analyzing observer reports of target and flanker identities.
• Employing mixture modeling to assess the contributions of different perceptual models.

Main Results:

• Similar flankers were reported significantly more often than dissimilar flankers, challenging the simple substitution model.
• Mixture modeling indicated that simple substitution accounts for at most half of the crowding errors.
• Pooling, which involves combining information from multiple items, underlies at least half of the reported crowding instances.

Conclusions:

• Simple substitution alone cannot explain the majority of flanker reports in crowding.
• Pooling of information from target and flanker items is a dominant mechanism in crowding.
• Understanding crowding requires considering both pooling and non-pooling (substitution) processes.