Abstract: Pigeons prefer signals for reinforcement that require greater effort (or time) to obtain over those that require less effort to obtain (T. S. Clement, J. Feltus, D. H. Kaiser, & T. R. Zentall, 2000). Preference was attributed to contrast (or to the relatively greater improvement in conditions) produced by the appearance of the signal when it was preceded by greater effort. In Experiment 1, the authors of the present study demonstrated that the expectation of greater effort was sufficient to produce such a preference (a second-order contrast effect). In Experiments 2 and 3, low versus high probability of reinforcement was substituted for high versus low effort, respectively, with similar results. In Experiment 3, the authors found that the stimulus preference could be attributed to positive contrast (when the discriminative stimuli represented an improvement in the probability of reinforcement) and perhaps also negative contrast (when the discriminative stimuli represented reduction in the probability of reinforcement).

Abstract: Three-year-old children were tested on three categorization tasks of increasing levels of abstraction (used with adult baboons in an earlier study): the first was a conceptual categorization task (food vs toys), the second a perceptual matching task (same vs different objects), and the third a relational matching task in which the children had to sort pairs according to whether or not the two items belonged to the same or different categories. The children were tested using two different procedures, the first a replication of the procedure used with the baboons (pulling one rope for a category or a relationship between two objects, and another rope for the other category or relationship), the second a task based upon children's prior experiences with sorting objects (putting in the same box objects belonging to the same category or a pair of objects exemplifying the same relation). The children were able to solve the first task (conceptual categorization) when tested with the sorting into boxes procedure, and the second task (perceptual matching) when tested with both procedures. The children were able to master the third task (relational matching) only when the rules were clearly explained to them, but not when they could only watch sorting examples. In fact, the relational matching task without explanation requires analogy abilities that do not seem to be fully developed at 3 years of age. The discrepancies in performances between children tested with the two procedures, with the task explained or not, and the discrepancies observed between children and baboons are discussed in relation to differences between species and/or problem-solving strategies.

Abstract: In 2 experiments, pigeons were trained on, and then transferred to, delayed simple discriminations in which the initial stimuli signalled reinforcement versus extinction following a retention interval. Experiment 1 showed that discriminative responding on the retention test transferred to novel test stimuli that had appeared in another delayed simple discrimination but not to stimuli having the same reinforcement history off-baseline. By contrast, Experiment 2 showed that performances transferred to novel initial stimuli whether they had been trained on-baseline or off-baseline. These results suggest that the test stimuli in delayed simple discriminations acquire control over responding only in the memory task itself. On the other hand, control by the initial stimuli, if coded as outcome expectancies, does not require such task-specific training.

Abstract: The traditional approach to the study of selective attention in animal discrimination learning has been to ask if animals are capable of the central selective processing of stimuli, such that certain aspects of the discriminative stimuli are partially or wholly ignored while their relationships to each other, or other relevant stimuli, are processed. A notable characteristic of this research has been that procedures involve the acquisition of discriminations, and the issue of concern is whether learning is selectively determined by the stimulus dimension defined by the discriminative stimuli. Although there is support for this kind of selective attention, in many cases, simpler nonattentional accounts are sufficient to explain the results. An alternative approach involves procedures more similar to those used in human information-processing research. When selective attention is studied in humans, it generally involves the steady state performance of tasks for which there is limited time allowed for stimulus input and a relatively large amount of relevant information to be processed; thus, attention must be selective or divided. When this approach is applied to animals and alternative accounts have been ruled out, stronger evidence for selective or divided attention in animals has been found. Similar processes are thought to be involved when animals search more natural environments for targets. Finally, an attempt is made to distinguish these top-down attentional processes from more automatic preattentional processes that have been studied in humans and other animals.

Abstract: Scotopic vision in horses (Equus caballus) was investigated using behavioral measurements for the first time. Four horses were tested for the ability to make simple visual discriminations of geometric figures (circles and triangles) under various brightness levels within an enclosed building. Measurements of brightness ranging from 10.37 to 24.12 magnitudes per square arcsecond (mag/arcsec2; in candelas per square meter--7.70 to 2.43E-05 cd/m2) were taken using a Sky Quality Meter. These values approximated outdoor conditions ranging from twilight in open country to a dark moonless night in dense forest. The horses were able to solve the discrimination problems in all brightness settings up to 23.77 mag/arcsec2 (3.35E-05 cd/m2). Moreover, they easily navigated their way around obstacles located within the testing area in extremely dim light (>23.50 mag/arcsec2; 4.30E-05 cd/m2), which were in conditions too dark for the human experimenters to see. These findings support physiological data that reveal a rod-dominated visual system as well as observations of equine activity at night.