Abstract: Eight crows were taught to discriminate overlapping pairs of visual stimuli (A+ B-, B+ C-, C+ D-, and D+ E-). For 4 birds, the stimuli were colored cards with a circle of the same color on the reverse side whose diameter decreased from A to E (ordered feedback group). These circles were made available for comparison to potentially help the crows order the stimuli along a physical dimension. For the other 4 birds, the circles corresponding to the colored cards had the same diameter (constant feedback group). In later testing, a novel choice pair (BD) was presented. Reinforcement history involving stimuli B and D was controlled so that the reinforcement/nonreinforcement ratios for the latter would be greater than for the former. If, during the BD test, the crows chose between stimuli according to these reinforcement/nonreinforcement ratios, then they should prefer D; if they chose according to the diameter of the feedback stimuli, then they should prefer B. In the ordered feedback group, the crows strongly preferred B over D; in the constant feedback group, the crows' choice did not differ significantly from chance. These results, plus simulations using associative models, suggest that the orderability of the postchoice feedback stimuli is important for crows' transitive responding.

Abstract: Using horses, we investigated three aspects of the stimulus control of lever-pressing behavior: stimulus generalization, discrimination learning, and peak shift. Nine solid black circles, ranging in size from 0.5 in. to 4.5 in. (1.3 cm to 11.4 cm) served as stimuli. Each horse was shaped, using successive approximations, to press a rat lever with its lip in the presence of a positive stimulus, the 2.5-in. (6.4-cm) circle. Shaping proceeded quickly and was comparable to that of other laboratory organisms. After responding was maintained on a variable-interval 30-s schedule, stimulus generalization gradients were collected from 2 horses prior to discrimination training. During discrimination training, grain followed lever presses in the presence of a positive stimulus (a 2.5-in circle) and never followed lever presses in the presence of a negative stimulus (a 1.5-in. [3.8-cm] circle). Three horses met a criterion of zero responses to the negative stimulus in fewer than 15 sessions. Horses given stimulus generalization testing prior to discrimination training produced symmetrical gradients; horses given discrimination training prior to generalization testing produced asymmetrical gradients. The peak of these gradients shifted away from the negative stimulus. These results are consistent with discrimination, stimulus generalization, and peak-shift phenomena observed in other organisms.

Abstract: Ten patients with semantic dementia resulting from bilateral anterior temporal lobe atrophy, and 10 matched controls, were tested on an object recognition task in which they were invited to choose (from a four-item array) the picture representing “the same thing” as an object picture that they had just inspected and attempted to name. The target in the response array was never physically identical to the studied picture but differed from it – in the various conditions – in size, angle of view, colour or exemplar (e.g. a different breed of dog). In one test block for each patient, the response array was presented immediately after the studied picture was removed; in another block, a 2 min filled delay was inserted between study and test. The patients performed relatively well when the studied object and target response differed only in the size of the picture on the page, but were significantly impaired as a group in the other three type-of-change conditions, even with no delay between study and test. The five patients whose structural brain imaging revealed major right-temporal atrophy were more impaired overall, and also more affected by the 2 min delay, than the five patients with an asymmetric pattern characterised by predominant left-sided atrophy. These results are interpreted in terms of a hypothesis that successful classification of an object token as an object type is not a pre-semantic ability but rather results from interaction of perceptual and conceptual processing.

Abstract: The landmark discrimination learning test can be used to assess the ability to utilize allocentric spatial information to locate targets. The present experiments examined the role of various factors on performance of a landmark discrimination learning task in beagle dogs. Experiments 1 and 2 looked at the effects of age and food composition. Experiments 3 and 4 were aimed at characterizing the cognitive strategies used in performance on this task and in long-term retention. Cognitively equivalent groups of old and young dogs were placed into either a test group maintained on food enriched with a broad-spectrum of antioxidants and mitochondrial cofactors, or a control group maintained on a complete and balanced food formulated for adult dogs. Following a wash-in period, the dogs were tested on a series of problems, in which reward was obtained when the animal responded selectively to the object closest to a thin wooden block, which served as a landmark. In Experiment 1, dogs were first trained to respond to a landmark placed directly on top of coaster, landmark 0 (L0). In the next phase of testing, the landmark was moved at successively greater distances (1, 4 or 10 cm) away from the reward object. Learning varied as a function of age group, food group, and task. The young dogs learned all of the tasks more quickly than the old dogs. The aged dogs on the enriched food learned L0 significantly more rapidly than aged dogs on control food. A higher proportion of dogs on the enriched food learned the task, when the distance was increased to 1cm. Experiment 2 showed that accuracy decreased with increased distance between the reward object and landmark, and this effect was greater in old animals. Experiment 3 showed stability of performance, despite using a novel landmark, and new locations, indicating that dogs learned the landmark concept. Experiment 4 found age impaired long-term retention of the landmark task. These results indicate that allocentric spatial learning is impaired in an age-dependent manner in dogs, and that age also affects performance when the distance between the landmark and target is increased. In addition, these results both support a role of oxidative damage in the development of age-associated cognitive dysfunction and indicate that short-term administration of a food enriched with supplemental antioxidants and mitochondrial cofactors can partially reverse the deleterious effects of aging on cognition.

Abstract: This study investigated chimpanzees' spontaneous spatial constructions with objects and especially their ability to repeat inter-object spatial relations, which is basic to understanding spatial relations at a higher level than perception or recognition. Subjects were six chimpanzees-four chimpanzees and two bonobos-aged 6-21 years, all raised in a human environment from an early age. Only minor species differences, but considerable individual differences were found. The effect of different object samples was assessed through a comparison with a previous study. A common overall chimpanzee pattern was also found. Chimpanzees repeated different types of inter-object spatial relations such as insertion (I), or vertical (V), or next-to (H) relations. However chimpanzees repeated I or V relations with more advanced procedures than when repeating H relations. Moreover, chimpanzees never repeated combined HV relations. Compared with children, chimpanzees showed a specific difficulty in repeating H relations. Repeating H relations is crucial for representing and understanding multiple reciprocal spatial relations between detached elements and for coordinating independent positions in space. Therefore, the chimpanzees' difficulty indicates a fundamental difference in constructive space in comparison to humans. The findings are discussed in relation to issues of spatial cognition and tool use.