Repeated acquisition and discrimination reversal in the squirrel monkey (Saimiri sciureus)

Area of Science:

• Behavioral neuroscience
• Cognitive psychology
• Animal behavior

Background:

• Repeated acquisition and discrimination reversal tasks are crucial for studying learning and cognitive flexibility.
• Variables controlling performance in these tasks are understudied, particularly in nonhuman primates.

Purpose of the Study:

• To investigate the controlling variables in repeated acquisition and discrimination reversal tasks.
• To understand factors influencing learning and cognitive flexibility in nonhuman primates.

Main Methods:

• Squirrel monkeys were trained on a touchscreen repeated acquisition task with daily novel stimulus pairs (S+/S-).
• Subjects performed discrimination acquisition followed by reversal learning with switched contingencies.
• Experimental analysis manipulated stimulus elements (S+ or S-) to assess their impact on learning rates.

Main Results:

• Both acquisition and reversal learning rates improved over sessions, but reversal learning remained slower than acquisition.
• This learning rate difference persisted across multiple days and intervening discriminations.
• Replacing individual stimulus elements (S+ or S-) with novel stimuli accelerated acquisition, suggesting contextual control by the stimulus complex.

Conclusions:

• The slower rate of reversal learning compared to acquisition is a reliable phenomenon.
• Contextual control by the entire stimulus complex, rather than individual stimulus properties, underlies this difference.
• Findings enhance understanding of fundamental aspects of discrimination acquisition and reversal learning.