Associative structure of second-order conditioning in humans

Area of Science:

• Cognitive Psychology
• Behavioral Neuroscience
• Learning and Memory

Background:

• Second-order conditioning (SOC) explains conditioned responding to a second stimulus (S2) following pairings of a first stimulus (S1) with an unconditioned stimulus (US), then S2 with S1.
• Existing theories propose either a direct S2→US association or an associative chain (S2→S1→US) to explain SOC.
• Prior research suggests S2-S1 pairing methods (sequential vs. simultaneous) influence responses to S2 after S1 extinction.

Purpose of the Study:

• To investigate whether S1 evoking S2 during S1 extinction explains differential responding to S2.
• To test if S1-evoked S2 paired with the absence of an outcome mediates extinction of S2.
• To evaluate the associative-chain account of SOC using human participants in two experiments.

Main Methods:

• Two experiments were conducted with human participants to examine second-order conditioning.
• Experiment 1 involved extinguishing S1 and S2 separately after SOC training, assessing effects on responding.
• Experiment 2 manipulated the timing of S2-S1 pairings relative to S1-alone exposures to prevent S2 evocation during S1 nonreinforcement.

Main Results:

• Extinguishing S1 reduced responding to S2 in both experiments, contradicting the S1-evocation hypothesis.
• Extinguishing S2 had minimal impact on S1 responding, despite S1 evocation during S2 extinction.
• Experiment 2 demonstrated that S2 responding mimicked S1 responding, varying with S1 reinforcement history, irrespective of S2 evocation.

Conclusions:

• The findings do not support the account that S1 evoking S2 during extinction mediates S2 extinction.
• Results provide additional evidence supporting the associative-chain (S2→S1→US) model of second-order conditioning.
• The study highlights the importance of the associative chain in understanding how learned associations are maintained and extinguished.