Visual working memory for letters varies with familiarity but not complexity.

Area of Science:

• Cognitive Psychology
• Neuroscience
• Visual Perception

Background:

• Visual working memory (VWM) has known limitations in information capacity and encoding rate.
• Stimulus complexity is a potential factor influencing these VWM limitations.

Purpose of the Study:

• To investigate the impact of stimulus complexity on the capacity and encoding rate of VWM.
• To determine if VWM limitations are based on the number of items or features processed.

Main Methods:

• Change-detection task using English letters (various fonts) and unfamiliar alphabets.
• Manipulation of stimulus complexity (perimetric complexity, κ) and encoding time.
• Estimation of VWM capacity (K) and encoding rate as a function of time.

Main Results:

• VWM capacity and encoding rate reached an asymptote regardless of stimulus complexity.
• Performance was best explained by item-based limitations (K), not feature-based limitations (K × κ).
• Familiar alphabets showed significantly higher encoding rates and capacities than unfamiliar ones.

Conclusions:

• VWM encoding rate and capacity are independent of stimulus complexity.
• Familiarity with stimuli, specifically familiar feature-integrated object representations, is the key determinant of VWM performance.
• These findings suggest that VWM operates on familiar, object-level representations rather than low-level features.