Familiarity with visual stimuli boosts recency bias in macaques

Area of Science:

• Cognitive neuroscience
• Animal behavior
• Primate cognition

Background:

• Understanding how non-human primates (NHPs) process dynamic visual information is crucial for comparative cognition.
• Temporal dynamic stimuli present unique challenges for perceptual decision-making.

Purpose of the Study:

• To investigate the strategies NHPs employ when decoding ambiguous temporal dynamic stimuli.
• To examine the influence of stimulus familiarity on decision-making strategies in NHPs.

Main Methods:

• A two-alternative forced choice task (2AFC) using dynamic movie snippets as cues.
• Ambiguous cues, drawn from the middle of animations, were presented in a subset of trials.
• Reward was administered randomly and independently of the animal's choice during ambiguous trials.

Main Results:

• NHPs demonstrated a clear decision strategy even with ambiguous cues, suggesting unawareness of non-differential reward.
• A significant recency effect was observed, with primates relying more on information from the end of the cue.
• This recency bias strengthened in sessions with familiar stimuli, despite offering no prior benefit.

Conclusions:

• NHPs exhibit a robust recency bias in temporal dynamic stimulus decoding.
• Stimulus familiarity can paradoxically amplify non-beneficial decision-making biases in NHPs.
• The observed bias may share mechanisms with human repetition biases, such as the illusory truth effect.