Functional equivalence classes in rats: Repeated olfactory discrimination reversals and delayed stimulus probes

Area of Science:

• Animal behavior
• Cognitive psychology
• Neuroscience

Background:

• Simultaneous matching-to-sample procedures are standard for studying stimulus equivalence in humans but have proven difficult in animals.
• Functional equivalence classes have been previously shown in pigeons and sea lions via concurrent repeated reversal discrimination.

Purpose of the Study:

• To investigate the feasibility of demonstrating functional equivalence classes in rats.
• To adapt and evaluate a concurrent repeated reversal discrimination procedure for rodent research.

Main Methods:

• Rats were trained on two sets of olfactory stimuli with reinforcement contingencies that were repeatedly reversed.
• Probe reversal sessions assessed transfer of function when novel stimuli within each set were introduced.
• Procedural modifications were implemented between Experiment 1 and Experiment 2.

Main Results:

• Experiment 1 showed weak and variable evidence of transfer of function.
• Experiment 2, with procedural changes, yielded strong evidence of transfer of function.
• Results indicate the formation of functional equivalence classes in rats.

Conclusions:

• The adapted concurrent repeated reversal discrimination procedure is effective for demonstrating functional equivalence classes in rats.
• This technique offers a viable strategy for investigating symbolic behavior in rodents.
• The findings advance the study of animal cognition and equivalence formation.