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An earlier informal experiment by Hudson (1950) in which rats learned to avoid a bundle of pipe cleaners presented only following shock is replica.ted and extended. Five groups of 20 Ss each received a single shock each while taking a sucrose pellet from a novel striped panel, A black-out period ranging from 1 to 40 sec. began with the onset of the 3/4 sec. shock. During the black-out the striped panel (forward-order CS) was removed; immediately following the black-out, a rubber toy hedgehog descended into the apparatus, Following a short exposure to the toy hedgehog and an intervening 24 hr. in the home cage, S was observed in the apparatus with the toy hedgehog at one end and the striped panel at the other. Control groups received either shock without the toy hedgehog or the toy hedgehog without the shock. All behavior was video recorded. Significant differential avoidance of the toy hedgehog occurred in the short inter stimulus interval groups (1, 5, and 10 sec.), but not in the 40 seCc group or in the control groups. In further analyses, individual’s were classified as differentially avoiding either the toy hedgehog, the striped panel, the shock location, the opposite end of the apparatus or no identifiable stimulus, according to two schemes. In the first, the basis of classification was differences in time spent in a normal posture at the two ends of the apparatus relative to a distribution of such differences in the unshocked control group. In the other, a combined score derived from differences in four other classes of behavior was the basis of classification. In both analyses, significant numbers of Ss from the 1, 5, and 10 sec. groups were identified as avoiding the toy hedgehog, while insignificant numbers of Ss from the 40 sec. and control groups did so. Only insignificant numbers of Ss avoided the striped panel. The results demonstrate that the "backward" association of the toy hedgehog with the shock is a reliable and robust phenomenon that can occur despite a 10 sec. UCS-CS delay, a single trial procedure, a 24-hr. delay between shock and testing, and the availability of a potential forward - order CS. The results cannot readily be explained either in terms of an unconditioned response to the toy hedgehog or simple sensitization. Both logical considerations and experimental results in backward conditioning preclude describing these results in terms of stimulus cuing. The results are interpreted as a. demonstration of the ability of rats to perceive causal agent-effect relationships in certain specific situations. Support for conclusions drawn from the inference that rats can make causal agent-effect connections is taken from the areas of belongingness, stimulus selection in avoidance learning, delayed taste -avoidance learning, novelty, reflexive aggression, and species-specific defense reactions. Theoretical literature relevant to this inference and the broader question of what is learned is discussed. / This thesis was digitized as part of a project begun in 2014 to increase the number of Duke psychology theses available online. The digitization project was spearheaded by Ciara Healy.

The first experiment sought specifically to determine whether variations in rats' overall run time in the alleyway reflect variations in the vigor of a single response, running (Hullian S-R view), or variations in the frequency of running relative to other, competing, behaviors, and not in the vigor of running ("response-competition" view). More broadly, the goal was a detailed descriptive account of the alleyway behavior of individual rats under a variety of typical experimental conditions. Six 23-hr. hungry rats were run for 75 trials in an alleyway to various amounts of reward, and the amount was shifted at several stages of training. Also, an environmental stimulus change was introduced during training. Six 23-hr. thirsty rats were run under comparable conditions. Overall run time was recorded and each trial was video-taped. Each run was then classified as a competing behavior trial (subject ceases forward progress after entering alleyway), an accessory behavior trial(subject shows some additional behavior while running forward, but no full competing behavior), or a direct run trial (only running occurs). The primary results were: (1) the decrease in run time in acquisition for each subject was due mainly to an orderly decrease in the amount of competing and accessory behavior, but the vigor of running also increased; (2) large changes in run time with other manipulations (differences in amount of reward in acquisition, shifts in amount of reward, extra stimulus, and proximity to reward) also reflected changes in amount of competing and accessory behavior, and smaller changes in the vigor of running; (3) the behavior of the thirsty rats was qualitatively the same as the behavior of the hungry rats, but was less affected by reward. The thirsty rats ran slower and showed more overall variability and more competing and accessory behavior than the hungry ones. The main implication of these results is that the alleyway is a multiple-response, selective-learning situation in which running both increases in vigor and gradually replaces other behaviors. The second experiment examined the structure of behavior in extinction to determine whether the increase in run time with non-reward reflects a return of competing and accessory behavior in the absence of selection for running. Secondary questions, not critical to a selective-learning view of the alleyway, were: (1) Would the addition of extra stimuli in acquisition which encourages competing behavior delay the return of high levels of competing behavior in extinction? (2) Does partial reinforcement in acquisition, which does retard extinction, do so through an increase in competing behavior in acquisition? Ten 23-hr, hungry rats were run in the alleyway to continuous reward (CRF), continuous reward with extra stimuli (CRF-S), or partial reward (PRF), for 59 trials. All were then run for at least 18 non-rewarded trials in extinction. The primary results were: (1) extinction following continuously rewarded acquisition did reflect a great return of competing and accessory behavior, of the same form as early in acquisition, consistent with the view of the alleyway as a selective-learning situation; (2) CRF-S rats showed slightly greater resistance to extinction than CRF rats; (3) the great resistance to extinction of the PRF rats was not a function of high levels of competing and accessory behavior in acquisition; (4) the PRF subjects showed much competing and accessory behavior and slow running in latter parts of the alleyway, and some continuously rewarded subjects showed similar behavior. This, plus observations in both experiments of recurrent behavior sequences across subjects and periods of atypically long run times for several subjects, suggests that an individual rat's behavior is not entirely independent of the behavior of other subjects run concurrently, though the mechanism underlying these interactions is not understood. / This thesis was digitized as part of a project begun in 2014 to increase the number of Duke psychology theses available online. The digitization project was spearheaded by Ciara Healy.