The Comparator Hypothesis: A Response Rule for The Expression of Associations

Spontaneous Recovery From Forward and Backward Blocking.

“…As previously mentioned, the comparator hypothesis (R. R. Miller & Matzel, 1988) could explain the recovery of suppression to X observed in the delay condition as a decrease in the effectiveness of A as a comparator stimulus. This decreased effectiveness of A as a comparator stimulus could have been due to CS A having lost its potential to control behavior during the retention interval (i.e., a weakening of the A-O association).…”

“…Experiment 2 also included a test of CS A. Testing A is theoretically relevant in the framework of the comparator hypothesis (R. R. Miller & Matzel, 1988) because the recovery of responding to the blocked CS observed after the retention interval in Experiment 1 could have been due either to a weakened activation of the indirect O representation during testing (i.e., due to the effective weakening of either the X-A association or the A-O association or both) or to an impairment of the comparator process per se (i.e., both the X-A and A-O associations may have been functional, but the impact of the indirect O representation on the direct O representation may wane with time). According to the comparator hypothesis, the activation of the indirect O representation during testing of X is a function of the product of the strengths of the X-A and A-O associations (i.e., Links 2 and 3, respectively, in Figure 1).…”

“…Experiment 3, also in sensory preconditioning, suggested that spontaneous recovery following both forward and backward blocking in Experiment 2 was due to impaired associative activation of the blocking stimulus' representation during testing with the blocked stimulus. Although no contemporary model of associative learning can explain these results, a modification of R. R. Miller and L. D. Matzel's (1988) comparator hypothesis is proposed to do so.Few findings in the associative learning literature have encouraged as much research as Kamin's (1968) report of the blocking effect. Blocking refers to impaired responding to a conditioned stimulus (CS), X, as a result of its being paired with an unconditioned stimulus (US) in the presence of another CS, A, which receives additional pairings with the US without CS X, relative to a control group that does not receive the additional A-US pairings.…”

“…Although this general view of forward blocking as a learning deficit was incorporated in most models of associative learning (e.g., Mackintosh, 1975;Pearce & Hall, 1980;Rescorla & Wagner, 1972;Wagner, 1981), it was rejected by R. R. Miller and Matzel's (1988; see also R. R. Miller & Schachtman, 1985) comparator hypothesis (see Figure 1). According to the comparator hypothesis, forward (as well as backward) blocking is due to a failure to express the X-US association during the presentation of CS X at test.…”

“…Experiment 1 as- Figure 1. The original comparator hypothesis (after R. R. Miller & Matzel, 1988). US ϭ unconditioned stimulus.…”