When saccharin or a light-tone compound was followed by electric shock, aa acquired aversion could be demonstrated to either cue. However, the optimal interval between conditioned stimulus (CS) and unconditioned stimulus (US) was strikingly different in the 2 cases: with a lighl^tone compound substantial aversion developed at 5 sec., and none at 210 sec.; with saccharin, substantial aversion developed at the longer interval, and none at 5 sec. This interaction is consistent with available data showing that exteroceptive but not gustatory cues are readily made aversive when paired with contiguous electric shook, while gustatory but not exteroceptive cues are readily made aversive when followed by delayed toxicosis. At the same time, it challenges the conventional assumption that such findings are due to a differential "belongingness" of the respective CSs and USs. A tentative account stressing the relative persistence of the stimulus trace generated by different CSs is offered, and its implications concerning the "generality of the laws of learning" are discussed.

A number of predictions derived from Bower's (1981) associative network model of mood and memory were investigated by inducing elated, neutral, or depressed moods in different groups of subjects. A mood-evaluation checklist verified the success of the mood-induction procedure. While in induced moods, subjects performed a lexical decision task in which the target stimuli were positive or negative trait adjectives, neutral nontrait adjectives, or nonwords. As predicted, subjects in elated moods showed facilitated processing of positive target words relative to processing of negative and neutral target words. Contrary to prediction, subjects in depressed moods did not respond faster to negative target words than they did to positive target words. Following the lexical decision task, subjects were administered an incidental free recall test for the words presented during the lexical decision task. Contrary to prediction, the three mood groups recalled similar numbers of words for each type of word target category. The asymmetric effects of elation and depression on memory that were observed in this study and a number of other studies are discussed.Fundamental to the predictive validity of Bower's (1981) associative network model of memory and emotion are two assumptions. The first is that specific emotions are represented as separate nodes in the same associative network as are words, concepts, and propositions of a verbal symbolic nature. The second assumption is that activation of an emotion node, by whatever means, will serve to lower the threshold of excitation of an associatively linked node via the process of spreading activation. This activation should increase the likelihood that related information would become more accessible to consciousness than it otherwise would, or at least become more accessible than information not associatively linked to the emotion node .

In the first experiment extensive hippocampal lesions retarded, but did not prohibit, the conditioning of a strong taste aversion to physiological saline (the conditioned stimulus; CS) when illness (the unconditioned stimulus; UCS) was induced by injecting rats with apomorphine 15 min following ingestion of the saline. In the second experiment hippocampal lesions reduced the aversiveness of novelty in a drinking fluid for the thirsty rat. It was suggested that the mild impairment of taste aversion learning in the rats with hippocampal lesions was not the result of destruction of mnemonic mechanisms that serve to span the long CS-UCS interval but rather that the reduced intensity of the aversion resulted from a lesionaltered neophobic disposition that weakened the saliency of the novel flavor CS.

The types of conditioned properties acquired by novel (i.e., nonpreexposedl or familiar (i.e., preexposedl exteroceptive cues that were paired with toxicosis, in the absence of a flavor CS, were evaluated in four experiments. In Experiment 1, the conditioned properties of novel exteroceptive cues served to block the acquisition of an aversion to a flavor CS during flavor conditioning and to suppress the ingestion response during flavor testing; animals failed to suppress their ingestion of either the flavor CS or a neutral flavor when tested in the absence of the exteroceptive CS, but suppressed their ingestion of both the flavor CS and the neutral flavor when tested in the presence of the exteroceptive CS. In Experiment 2, preexposed exteroceptive cues that had been paired with toxicosis failed to provide evidence of such conditioned properties. Experiment 3 demonstrated that preexposed contextual cues that were reinforced in compound with novel exteroceptive cues failed to acquire the conditioned properties acquired by nonpreexposed contextual cues under the same conditions of reinforcement. Finally, in Experiment 4, the conditioned properties of the novel exteroceptive cues served to evoke a conditioned gastrointestinal response that gradually extinguished as a function of repeated nonreinforced exposures to the exteroceptive cues, and, in the absence of such extinction, the conditioned properties served to block the acquisition of a flavor aversion.

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