The informational properties of S1, S2, and the S1–S2 sequence on conditioned suppression

Abstract

The Egger-Miller information hypothesis was tested in a nonoverlapping compound stimulus CER situation. During CER training, S2, the so-called redundant stimulus, acquired greater suppression qualities than SI. However, following CER training, subjects were exposed to test situations in which the independent suppression qualities of SI and S2 were assessed. SI was followed by a trace interval, S2 was presented alone, or the SI-S2 sequence was reversed. Results of all test conditions showed minimal suppression to S2, whi1e suppression to SI was maintained or facilitated. It was suggested that S2, a1though a redundant predictor of shock occurrence, provides information as to "when" shock is due.The present study attempted to extend the Egger-Miller information hypothesis (Egger & Miller, 1962) to a classical aversive situation as well as resolve some of the inconsistent results obtained in previous studies which employed aversive stirnulation, According to the information hypothesis, if two or more successive stimuli precede primary reinforcement, the first stimulus to occur, provided it is reliab1e, should become the more effective conditioned reinforcer. Normally, the second stimulus, because it is a redundant predictor of rein forcement, should not acquire conditioned reinforcing properties. The hypothesis was derived from studies investigating conditioned positive reinforcers in instrumental appetitive situations (Egger & Miller, 1962; 1963), and supported by McCausland, Menser, Dernpsey, and Birkimer (1967).The results obtained in aversive situations, however, have failed to show consistent support for the hypothesis. In a punishment situation, Seligman (1966) obtained support for the "weak" form of the hypothesis, showing greater suppression of the punished operant during the first stimulus than during the second stimulus. The second stimulus, however, did suppress behavior more than an event not explicitly paired with shock. Seligman suggested that the punishing power of the second stimulus resuIted from its temporal contiguity with shock rather than its informational properties. Ayers (1967), using a conditioned suppression paradigm, demonstrated that redundant stimuli produced as much suppression as their more informative counterparts. Scheuer and Keeter (1969) confirmed Ayers' resuIts using nonoverlapping rather than the overlapping compounds as Ayers had used. However, Reprints may be obtained from Dr. Cynthia Scheuer, Department of Psychology, Florida Atlantic University, Boca Raton, Florida 33431. 39both Ayers and Scheuer and Keeter utilized the ongoing suppression ratios as indices of the conditioned reinforcing properties of each stimulus within the compound. Thus, the suppression obtained during the second stimulus could have been a result of a number of factors other than its informational qualities. The S2 suppression may have resulted from (1) its temporal eontiguity to shock as Seligman suggests, (2) the informational properties of SI termination independently of S2 presentation, or (3) th...

Temporal primacy overrides prior training in serial compound conditioning of the rabbit’s nictitating membrane response

“…Previous findings have indicated that the impairment of responding seen when CSB is tested by itself does not seem to appear inside the context of the compound. First, considerable responding during CSB has been observed when assessed inside the context of the serial compound (Gaioni, 1982;Kehoe, 1979;Seger & Scheuer, 1977). Similarly, in the present experiments, responding during the serial compound occurred largely during CSB.…”

The conditioned suppression and enhancement of avoidance during a serial compound CS

“…However, the suppressive influence found for S2 in the stimulus sequence also extinguished when the US was removed in Phase 5 (although, in contrast to S1, an enhancement capability did not develop). These data support a view that a CS must predict an imminent US for conditioned avoidance suppression to be maintained (for a similar view, see Seger & Scheuer, 1977).…”

Serial order of conditional stimuli as a discriminative cue for Pavlovian conditioning

“…The highest rates of responding were found when B was preceded by A (i.e., the reinforced sequence), but there was also strong responding whenever B occurred as the second stimulus, regardless of the preceding element (B → B, X → B). This pattern might suggest a strong association between the element B and the US particularly if it occurred later in the trial pair, much like the account described earlier for the experiment by Seger and Scheuer (1977). There was further evidence that response rates were high to the specific reversal of the A-B sequence (i.e., when B was followed by A).…”

“…The work that has been conducted has yielded results consistent with the hypothesis that animals can acquire temporal order information during Pavlovian conditioning. Seger and Scheuer (1977) showed that responding was greater to the second CS of two successively presented CSs that preceded a US (A → B → US) than to that same stimulus when it was presented at the beginning of the extinguished trial (B → A → no US). The solution of this simple discrimination, however, does not provide convincing evidence that the animals have encoded or represented the temporal order of the two cues.…”