Selective Attention in Animal Discrimination Learning

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.     

Preference for the outcome that follows a relatively aversive event: Contrast or delay reduction?

Pigeons prefer a positive discriminative (S+) stimulus that follows a less preferred event (a large number of required responses, a longer delay, or the absence of food) over a different S+ with a similar history of reinforcement that follows a more preferred event (a single required response, no delay, or food). We proposed that this phenomenon results from contrast (referred to as within-trial contrast) between the less preferred initial event and the signal for reinforcement. Delay reduction theory (Fantino, 1969) can account for these results by proposing that the less preferred initial event lengthens the duration of the trial, thereby allowing the S+ stimulus to occur later in the trial and thus become a better predictor of reinforcement. In the present experiments, we further explored this effect. In Experiment 1, we controlled for trial duration by using a fixed ratio response (30 pecks) as one initial event and the absence of pecking for the same duration as the other initial event (0 pecks). The pigeons showed a reliable preference for the positive stimulus that followed the least preferred initial event. In Experiment 2, we controlled for trial duration by using 30 pecks as one initial event and 1 peck followed by a delay that matched the duration of the preceding 30-peck trial. (Group Time Same). For Group Time Different, there was no delay following the 1-peck initial event. For Group Time Same, preference for the initial event negatively predicted the pigeons’ preference for the S+ stimulus that followed, supporting the contrast account. A somewhat greater preference for the discriminative stimulus that followed the least preferred initial event was found for Group Time Different suggesting that in addition to contrast, delay reduction also may play a small role. However, the greater initial-event preference found for Group Time Different suggests that contrast can account for the group difference as well.     

Contrast between what is expected and what occurs increases pigeon’s suboptimal choice

Animal Cognition - When pigeons are given a choice between 50% signaled reinforcement and 100% reinforcement they typically do not choose optimally, sometimes even preferring 50% reinforcement....     

Transitive inference in pigeons: Control for differential value transfer

Transitive inference (TI) effects have been demonstrated in several nonhuman species using a nonverbal version of the task in which A is better than B is represented in a simple simultaneous discrimination, A+B?. Following five-term training (e.g., A+B?, B+C?, C+D?, D+E?), the choice of B over D on test trials is taken as evidence of TI. Recently, differential value transfer from the S+ to the S? in a simultaneous discrimination has been proposed as a noncognitive basis for these effects. Two experiments were conducted to control for differential value transfer. The results suggest that differential value transfer is not the only basis for nonhuman TI performance. An alternative account based on spatial mapping is discussed.     

Rating scales for hyperactivity: Concurrent validity,reliability, and decisions to label for the Conners and Davids abbreviated scales

Rating scales have become the instrument of choice in labeling and assessing change in behavior of hyperactive children. However, several criticisms have recently have levied against their use. The present investigation examined the concurrent validity, and inter- and intrarater reliability for the Abbreviated Teacer Questionnaire (ATQ, Conners, 1973) and the Rating Scales for Hyperkinesis (Davids, 1971). Sixteen teachers from two special and two regular schools (grades 1-4) rated 211 normal and 49 special children using both scales. High correlations were found suggesting excellent predictability between scales and considerable stability across time and rater. Lower scores on a subsequent rating relative to an initial rating were demonstrated, dependent on time between ratings but independent of (a) teacher expectation of treatment gains, (b) bias produced by rating selected children, and (c) whether children were hyperactive or normal. Use of initial and infrequent rating scores versus subsequent, closely spaced ratings was related to the rater's objective (e.g., diagnosis, treatment, or assessment).     

Temporal parameters of the feature positive effect

Trial duration and intertrial interval duration were parametrically varied between groups of pigeons exposed to a discrimination involving the presence vs. the absence of a dot. Half the groups received the dot as the positive stimulus (feature positive groups) and half the groups received the dot as the negative stimulus (feature negative groups). Faster learning by the feature positive birds (feature positive effect) was found when the trial duration was short (5 sec) regardless of whether the intertrial interval was short (5 sec) or long (30 sec). No evidence for a feature positive effect was found when the trial duration was long (30 sec) regardless of the length of the intertrial interval (30 sec or 180 sec). The results suggest that short trial duration is a necessary condition for the occurrence of the feature positive effect, and neither intertrial interval nor trial duration/intertrial interval ratio are important for its occurrence. The suggestion that mechanisms underlying the feature positive effect and autoshaping might be similar was not supported by the present experiment since the trial duration/intertrial interval ration parameter appears to play an important role in autoshaping but not the feature positive effect.     

Interval timing with gaps: gap ambiguity as an alternative to temporal decay

C. V. Buhusi, D. Perera, and W. H. Meck (2005) proposed a hypothesis of timing in rats to account for the results of experiments that have used the peak procedure with gaps. According to this hypothesis, the introduction of a gap causes the animal's memory for the pregap interval to passively decay (subjectively shorten) in direct proportion to the duration and salience of the gap. Thus, animals should pause with short, nonsalient gaps but should reset their clock with longer, salient gaps. The present authors suggest that the ambiguity of the gap (i.e., the similarity between the gap and the intertrial interval in both appearance and relative duration) causes the animal to actively reset the clock and prevents adequate assessments of the fate of timed intervals prior to the gap. Furthermore, when the intertrial interval is discriminable from the gap, the evidence suggests that timed intervals prior to the gap are not lost but are retained in memory.     

Timing in pigeons: The choose-short effect may result from pigeons’ “confusion” between delay and intertrial intervals

In conditional discriminations, when samples differ only in duration, pigeons typically show a choose-short effect (i.e., higher matching accuracy on short-duration-sample than on long-durationsample trials with increasing delay between sample and comparison stimuli). That this effect depends on the similarity of retention interval (RI) and intertrial interval (ITI) houselight illumination conditions has been taken as evidence that pigeons judge duration relative to a temporal background. In the present experiment, pigeons trained with duration samples and with the ITI either illuminated or not showed a choose-short bias only when the RI illumination on test trials was the same as the ITI illumination had been in training. The results support the hypothesis that the choose-short effect results from the pigeons’ confusion between the ITI and the RI.     

Effects of color stimulation and information on the copying performance of attention-problem adolescents

The optimal stimulation theory proposes that hyperactive children are less tolerant of lower levels of arousal than nonhyperactive children and should thus derive greater gains from stimulation added to repetitive copying tasks than do comparisons. To test this hypothesis, 16 adolescents, rating high on attention and behavior problems, were matched on the basis of age and poor handwriting performance to 16 controls. Matched pairs were randomly assigned to treatment order (high-stimulation colored letters followed in 2 weeks by low-stimulation black letters or the reverse order) and to level of information (color added to difficult letter parts or added to randomly selected letters), counterbalanced for treatment order and level of information within each order. Errors and activity were subjected to a mixed-design analysis of covariance, with IQ the covariate. The major findings indicated that attention-problem adolescents performed better with high-stimulation task stimuli than with low, relative to the opposite performance pattern of controls. Different responding was significant for experimental but not for control children.This research was supported by National Institute of Mental Health Grant MH32282 to the first author.