Interference and auditory short-term memory in the bottlenosed dolphin

Interference in auditory short-term memory in the bottlenosed dolphin,Tursiops truncatus (Montagu), was studied using a delayed matching-to-sample task. At each trial, one of two sample sounds, chosen randomly, was projected underwater for 4 sec and then, after a variable delay interval, both sounds were presented. A response to the sound matching the initial sample was reinforced. Correct matching was significantly reduced following short intervals between trials in combination with long delays after the sample (proactive interference), or when a near continuous irrelevant sound was inserted into the delay interval (retroactive interference). There was rapid habituation to interference if the irrelevant sound was short in duration relative to the delay interval. For both proactive and retroactive interference, the errors were predominantly responses to the sample sound appropriate to the prior trial rather than to the current trial, indicating that memory for the relative recency of events (temporal memory) was degraded by interference. When interference was deleted or minimized, temporal memory remained nearly perfect over 30-sec delay intervals, the longest tested. The importance of distinguishing between temporal memory and nontemporal, or event, memory in different forms of the delayed matching task was emphasized.     

Perseveration of associative strength in rabbit nictitating membrane response conditioning following ISI shifts

The present experiment determined whether associative strength based upon 15 CS-US pairings at various interstimulus intervals (ISIs) could survive shifts of the ISI to influence the subsequent acquisition of the nictitating membrane (NM) CR. The choice of 15 preshift pairings was based upon previous work, which had shown that this training level produced substantial associative strength without NM CR acquisition. Consequently, this experiment, by shifting the ISI before the beginning of CR acquisition, served as an extension to traditional ISI-shift studies that have imposed the manipulation after CR acquisition. The findings of the experiment indicated that 15 preshift pairings in Stage 1 at ISIs from 250 to 4,000 msec were as effective as 15 pairings at a 500-msec ISI in determining the number of trials to the first NM CR in Stage 2 in which the training ISI was 500 msec. Moreover, 15 pairings in Stage 1 at ISIs from 250 to 2,000 msec were equivalent to 15 pairings at 500 msec in controlling the number of trials to 10 successive NM CRs in Stage 2. These outcomes demonstrate that, within a large ISI range, the associative strength based upon relatively few pairings is preserved despite various shifts of the ISI. Therefore, these results suggest that the reductions in CR performance, which have been consistently observed in traditional studies following ISI shifts, are not due to the loss of associative strength.     

Genetic influences in different aspects of language development: the etiology of language skills in 4.5-year-old twins

The genetic and environmental etiologies of diverse aspects of language ability and disability, including articulation, phonology, grammar, vocabulary, and verbal memory, were investigated in a U.K. sample of 787 pairs of 4.5-year-old same-sex and opposite-sex twins. Moderate genetic influence was found for all aspects of language in the normal range. A similar pattern was found at the low end of the distribution with the exception of two receptive measures. Environmental influence was mainly due to nonshared factors, unique to the individual, with little influence from shared environment for most measures. Genetic and environmental influences on language ability and disability are quantitatively and qualitatively similar for males and females.     

Certainty of Punishment and Criminal Thinking: Do the Rational and Non-rational Parameters of a Student’s Decision to Cheat on an Exam Interact?

The purpose of this study was to determine whether criminal thinking interacts with the rational requirements of human decision-making in a group of college students. A convenience sample of 315 undergraduates (114 males, 201 females) completed self-report measures of criminal thinking and estimated their likelihood of cheating on an exam given different levels of certainty of apprehension. A repeated-measures analysis of covariance revealed that students were significantly more likely to seize on the opportunity to cheat when the certainty of getting caught was 10% than when it was 50% and that students with higher levels of criminal thinking were more likely to take the opportunity to cheat than students with lower levels of criminal thinking. In addition, students exhibiting moderate proactive criminal thinking and moderate to high reactive criminal thinking were significantly less likely to be deterred from cheating when the odds of getting caught were low.     

Adjunctive drinking during variable and random-interval food reinforcement schedules

Rats were trained to leverpress for food and subsequently exposed to either arithmetic series or random variable-interval reinforcement schedules. Adjunctive drinking developed in all subjects exposed to arithmetic variable-interval reinforcement, but did not develop in six of the eight animals trained on the random schedule. The results suggest that adjunctive drinking is the result of an interaction between the tendency of rats to drink after eating and the ability of locally low probabilities of reinforcement within schedules to induce conditioned behavioral states.     

Practicum Placement in a Counseling-Employment Agency for Disadvantaged Youth

In order to emphasize the development of skills in helping the culturally disadvantaged, graduate students were given practicum placement in a Department of Labor-financed agency which gave counseling and employment training to disadvantaged youth. Students attended staff meetings, interviewed staff members concerning the work they performed, and discussed client contacts with caseworkers, in addition to interviewing agency clients. Increased awareness of problems, broadened conceptualizations, and expansion of interpersonal skills were seen as advantages of the practicum. Limitations included some lack of goal clarity and inefficiency of time use in dealing with this clientele.