Adaptation biases the parallel perception of subitized numerosities.

Area of Science:

• Cognitive psychology
• Visual perception
• Numerical cognition

Background:

• Numerosity adaptation typically affects perception of moderate quantities (>4).
• Subitizing (rapid estimation of 1-4 items) is considered a distinct, non-adaptive process.
• This study explores adaptation's influence on the subitizing range.

Purpose of the Study:

• To investigate if subitizing (estimation of 1-4 items) is susceptible to numerosity adaptation.
• To determine if adaptation effects differ based on target information timing (before vs. after stimulus presentation).

Main Methods:

• Participants adapted to a 50-dot stimulus.
• Stimuli with 1-5 colored dots were presented.
• Participants estimated numerosities of single sets, total dots, or subsets.
• Target color information was provided either before or after stimulus presentation.

Main Results:

• No adaptation effect was observed for single sets or total dot estimation (CV < 0.05), confirming effective subitizing.
• When estimating parallel subsets, adaptation biased numerosity estimation.
• Subitizing adaptation effects (CV) correlated with moderate numerosity adaptation (5-12 dots).
• Adaptation effects were stronger when target information was revealed after stimulus presentation.

Conclusions:

• Subitizing is not immune to numerosity adaptation when estimating subsets.
• Parallel subset enumeration may override subitizing, engaging general numerosity estimation processes.
• The timing of target information influences adaptation strength, suggesting adaptive weighting of prior stimuli under uncertainty.