Conditional and unconditional components of post-shock freezing

Rats received shocks in one apparatus, and post-shock “freezing” was then assessed in that apparatus or in a different one. The assessment of freezing was made immediately after shock or after a 24-hour delay. Post-shock freezing was reduced when the animals were tested in a different apparatus from that in which shocks had been administered. No reduction in freezing was caused by the 24-hour delay. All the post-shock freezing was therefore attributable to contextual cues and to generalization between contexts. This pattern of results suggests that post-shock freezing is entirely produced by conditioned fear elicited by cues associated with shock and that no part of post-shock freezing is an unconditional response (UR) directly elicited by shock.