Is Categorization in Visual Working Memory a Way to Reduce Mental Effort? A Pupillometry Study.

Area of Science:

• Cognitive Psychology
• Neuroscience

Background:

• Visual working memory (VWM) stores information as continuous (e.g., specific shade) or categorical (e.g., general color) representations.
• It is assumed continuous representations are more effortful than categorical ones, but this has not been directly tested.

Purpose of the Study:

• To investigate the mental effort associated with continuous versus categorical representations in VWM.
• To determine how VWM capacity affects the effort and precision of different representation types.

Main Methods:

• A delayed estimation task was used, measuring pupil size as an indicator of mental effort.
• Participants memorized 1-4 ambiguous (encouraging continuous) or prototypical (encouraging categorical) colors.
• Memory precision was assessed after a delay using a probe.

Main Results:

• At low memory load (1 item), maintaining ambiguous colors (continuous) increased pupil size (effort) without reducing precision.
• At high memory load (4 items), pupil size decreased for ambiguous colors, and precision was significantly reduced.
• This suggests a shift towards less effortful, but less precise, categorical representations for ambiguous colors under high load.

Conclusions:

• Continuous representations in VWM are more mentally effortful than categorical ones.
• VWM capacity is limited, with potentially only one continuous representation being maintainable simultaneously.
• The brain flexibly adjusts representation strategies based on memory load and item ambiguity.