Acquisition and maintenance of autoshaped key pecking by pigeons were studied as a function of the duration of trial and intertrial intervals'. In Experiment 1, trial durations were fixed and intertrial durations were variable. Twenty-five groups of birds were studied at trial durations ranging from 1 to 64 sec and mean intertrial interval durations ranging from 6 to 768 sec. Values were chosen so as to obtain several groups with the same ratio of intertrial interval to trial duration. Ratios ranged from 2:1 to 96:1. Over most durations studied, constant values of the ratio produced an approximately constant number of trials to acquisition. High ratios resulted in faster acquisition than did low ratios. Following acquisition, response rate varied inversely with absolute trial duration. In Experiment 2, intertrial interval as well as trial durations were fixed. Intertrial intervals ranged from 48 to 384 sec, and trial durations ranged from 8 to 32 sec. Trials to acquisition again varied inversely with the ratio of intertrial interval to trial duration. In both experiments, this relationship was well approximated by a single power function. These results are shown to strain several current accounts of the classical conditioning process.

The study of animal personality has attracted considerable attention, as it has revealed a number of similarities in personality between humans and several nonhuman species. At the same time the adaptive value and evolutionary maintenance of different personalities are the subject of debate. Since Pavlov’s work on dogs, students of comparative cognition have been aware that animals display vast individual differences on cognitive tasks, and that these differences may not be entirely accounted for differences in cognitive abilities. Here, we argue that personality is an important source of variation that may affect cognitive performance and we hypothesise mutual influences between personality and cognition across an individual’s lifespan. In particular, we suggest that: 1) personality profiles may be markers of different cognitive styles; 2) success or failure in cognitive tasks could affect different personalities differently; 3) ontogenetic changes of personality profiles could be reflected in changes in cognitive performance. The study of such interplay has implications in animal welfare as well as in neuroscience and in translational medicine.

The acquisition, maintenance, and extinction of autoshaped responding in pigeons were studied under partial and continuous reinforcement. Five values of probability of reinforcement, ranging from .1 to 1.0, were combined factorially with five values of intertrial interval ranging from 15 to 250 sec for different groups. The number of trials required before autoshaped responding emerged varied inversely with the duration of the intertrial interval and probability of reinforcment, but partial reinforcement did not increase the number of reinforcers before acquisition. During maintained training, partial reinforcement increased the overall rate of responding. A temporal gradient of accelerated responding over the trial duration emerged during maintenance training for partial reinforcement groups, and was evident for all groups in extinction. Partial reinforcement groups responded more than continuous reinforcement groups over an equivalent number of trials in extinction. However, this partialreinforcment extinction effect disappeared when examined in terms of the omission of "expected" reinforcers.

Sixty Heterogeneous Stock (HS) mice received a battery of six problem‐solving tasks and three control procedures. The problem‐solving tasks included Hebb‐Williams, a place learning task conducted in a plus maze, radial maze, a working memory test following the radial maze, a set of detour problems and a visual non‐matching to sample task. The control procedures consisted of land and water activity measures and a light‐dark test. The correlation matrix derived from these tasks did not exhibit positive manifold, that is, positive correlations across all problem‐solving tasks. Principal components analysis reduced the correlation matrix to four components with eigenvalues exceeding 1.0. Instead of the general factor solution common in the study of human problem‐solving, this component structure appeared more congenial to a modular interpretation, with the four components each explaining approximately the same magnitude of matrix variance.

The role of the stimulus-reinforcer contingency in the development and maintenance of lever contact responding was studied in hooded rats. In Experiment I, three groups of experimentally naive rats were trained either on autoshaping, omission training, or a random-control procedure. Subjects trained by the autoshaping procedure responded more consistently than did either random-control or omission-trained subjects. The probability of at least one lever contact per trial was slightly higher in subjects trained by the omission procedure than by the random-control procedure. However, these differences were not maintained during extended training, nor were they evident in total lever-contact frequencies. When omission and random-control subjects were switched to the autoshaping condition, lever contacts increased in all animals, but a pronounced retardation was observed in omission subjects relative to the random-control subjects. In addition, subjects originally exposed to the random-control procedure, and later switched to autoshaping, acquired more rapidly than naive subjects that were exposed only on the autoshaping procedure. In Experiment II, subjects originally trained by an autoshaping procedure were exposed either to an omission, a random-control, or an extinction procedure. No differences were observed among the groups either in the rate at which lever contacts decreased or in the frequency of lever contacts at the end of training. These data implicate prior experience in the interpretation of omission-training effects and suggest limitations in the influence of stimulus-reinforcer relations in autoshaping.

Current theoretical approaches to animal intelligence either in the form of adaptive specializations or general processes make no explicit predictions nor do they provide substantial evidence concerning individual differences in problem solving. Two strains of mice (Mus musculus) were run through a battery of water escape tasks consisting of 4 spatial learning tasks, a visual discrimination task, and an activity control. The 2 strains were the second filial generation (F 2) from a cross between C57BL/6 and DBA/2Js inbred strains and a CD-I outbred strain. Results indicated positive correlations across all learning tasks in both strains for latency and error measures. Factor analysis revealed a significant first factor for these measures in both strains. These results suggest that at least some spatial and visual tasks in mice under this motivational condition share common properties.

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Two experiments examined the structure of individual differences in mice by means of tasks that produced significant acquisition within 1 session. In Experiment 1, 5 cognitive tasks-detour, winshift, olfactory discrimination, fear conditioning, and operant acquisition-were used in conjunction with two control procedures: an open field and a light- dark test. In Experiment 2, some modifications were made to the tasks used in the 1st experiment, and 3 new tasks were used in conjunction with the same control procedures. The battery consisted of 5 learning tasks: detour, Hebb-Williams, radial maze, olfactory foraging, and fear conditioning. Results of both experiments indicate that when cognitive tasks and control procedures were included in principal-components analyses most of the variance attached principally to individual tasks rather than to a general component as is found typically in human cognitive batteries. When control procedures were eliminated, there was better evidence for the presence of a general cognitive factor, particularly in Experiment 2.