Blocking is not 'pure' cue competition: Renewal-like effects in forward and backward blocking indicate contributions by associative cue interference

Abstract

Blocking (i.e., reduced responding to cue X following YX-outcome pairings in Phase 2 as a consequence of cue Y having been paired with the outcome in Phase 1) is one of the signature phenomena in Pavlovian conditioning. Its discovery promoted the development of multiple associative models, most of which viewed blocking as an instance of pure cue competition (i.e., a decrease in responding attributable to training two conditioned stimuli in compound). Two experiments are reported in which rats were examined in a fear conditioning paradigm (i.e., lick suppression), and context dependency of retrieval at test was used as an index of associative cue interference (i.e., a decrease in responding to a target cue as a result of training a second cue with the same outcome but without concurrent presentation of the two cues). Specifically, we observed renewal of forward-blocking which parallels renewal of proactive interference, and renewal of backward-blocking which parallels renewal of retroactive interference. Thus, both backward-blocking (Experiment 1, embedded in a sensory preconditioning design) and forward-blocking (Experiment 2, conducted in first-order conditioning) appear to be influenced by retroactive and proactive interference, respectively, as well as cue competition. Consequently, blocking, long regarded as a benchmark example of pure cue competition, is sometimes a hybrid of cue competition and associative interference. Finally, the Discussion considers whether stimulus competition and associative interference are two independent phenomena or products of a single underlying process. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Figure 1:

Results of Experiment 1. Mean times to complete 5 cumulative s of drinking in the presence of the target CS X. Therefore, 0.7 log s is the lowest possible score. Higher scores represent stronger responding to the target CS. B-Block = Backward Blocking, R-Inter = Retroactive Interference, P = paired (i.e., Y signaled footshock [+] in Phase 2), Unp = Outcome unsignaled in Phase 2. Error bars represent standard error of the means. See text and Table 1 for details.

Figure 2:

Results of Experiment 2. Mean times to complete 5 cumulative s of drinking in the presence of the target CS X. Therefore, 0.7 log s is the lowest possible score. Higher scores represent stronger responding to the target CS. F-Block = Forward Blocking, P-Inter = Proactive Interference, P = paired (i.e., Y signaled footshock [+] in Phase 1), Unp = footshock unsignaled in Phase 1. Error bars represent standard error of the means. See text and Table 2 for details.