Quantity judgments of sequentially presented food items by capuchin monkeys (Cebus apella)

Recent assessments have shown that capuchin monkeys, like chimpanzees and other Old World primate species, are sensitive to quantitative differences between sets of visible stimuli. In the present study, we examined capuchins’ performance in a more sophisticated quantity judgment task that required the ability to form representations of food quantities while viewing the quantities only one piece at a time. In three experiments, we presented monkeys with the choice between two sets of discrete homogeneous food items and allowed the monkeys to consume the set of their choice. In Experiments 1 and 2, monkeys compared an entirely visible food set to a second set, presented item-by-item into an opaque container. All monkeys exhibited high accuracy in choosing the larger set, even when the entirely visible set was presented last, preventing the use of one-to-one item correspondence to compare quantities. In Experiment 3, monkeys compared two sets that were each presented item-by-item into opaque containers, but at different rates to control for temporal cues. Some monkeys performed well in this experiment, though others exhibited near-chance performance, suggesting that this species’ ability to form representations of food quantities may be limited compared to previously tested species such as chimpanzees. Overall, these findings support the analog magnitude model of quantity representation as an explanation for capuchin monkeys’ quantification of sequentially presented food items.

Reported prevalence of attentional difficulties in a general sample of college students

The present study investigated the self-reported prevalence of attention-deficit hyperactivity disorder (ADHD)symptoms in 770 college students using the Adult Rating Scale and the Wender Utah Rating Scale. Psychometric properties of these scales were explored. The study also investigated the performance of students with ADHD symptoms, relative to students without ADHD symptoms, on a battery of neuropsychological tasks. Results revealed that 7 and 8% of the students reported significant symptoms (i.e., 1.5 SD above the mean) on the Adult Rating Scale and the Wender Utah Rating scale, respectively, and 2.5% reported significant symptoms on both the Adult Rating Scale and the Wender Utah Rating Scale. Using more stringent criteria (two standard deviations), fewer (i.e, 4, 3.8%, and 0.5%) subjects reported significant symptoms associated with ADHD. Between-group differences were found on one of the neuropsychological tasks. The construct validity of the rating scales was supported. Limitations and implications for future research are advanced.Presented at the International Neuropsychological Society's Sixteenth European Conference, Angers, France, June 1994, and the Annual Convention of the American Psychological Association, Los Angeles, CA, August 1994.     

A HULLIAN CONSTANT AS AN INDEX OF INTELLIGENCE: TWO EMPIRICAL INVESTIGATIONS

Following Clark Hull, it is widely considered that the asymptote of the learning curve represents motivational factors, but that rate of approach to asymptote ('i') represents associational factors. The suggestion that i may be a measure of intelligence was tested empirically in two studies. An initial exploratory study yielded a positive correlation between i and IQ. A more rigorous replication did not. The results are discussed briefly.     

Children's language acquisition

Child language acquisition has only recently become an important research topic for developmental psychologists, although the universal appearance of language during the second year of life has long fascinated philosophers. For normally developing children, language emerges spontaneously as a means of talking about what they know so that they can accomplish social goals important to them. Some children, however, need to be taught. This article reviews current issues in child language acquisition and suggests a research agenda for helping those children who have difficulty mastering the fundamentals of language.     

Some evidence in support of a relationship between human auditory signal-detection performance and the phase of the alpha cycle

This study concerned the hypothesis presented by Lindsley in 1961 that human sensorimotor performance should vary with the phase of the alpha cycle. Although there have been a number of studies which have supported this hypothesis, there has been no work from a modality other than the visual modality. Since eye tremor is correlated in phase and frequency with the alpha rhythm, these visual results might be explained by the peripheral eye tremor and not necessarily by the central alpha rhythm. The present study measured human auditory signal-detection performance at four different phases of the temporally (T5-linked mastoids) measured alpha rhythm. These four different phases were defined on an a priori basis by a computer algorithm. Detection performance was significantly better at the negative peak of this alpha cycle than at the positive peak, but there was no significant difference between the positively and negatively going zero cross performances. These results are consistent with the Lindsley hypothesis.     

Response to Requests for Abortion: The Influence of Guilt and Knowledge1

Participants who varied in their levels of sex guilt and sexual knowledge indicated the extent of their approval for abortion in response to 10 case histories of abortion applicants. The case histories were varied in terms of the circumstances under which conception had occurred. Sex guilt was significantly related to abortion decisions while sexual knowledge registered little effect. Low sex guilt students were more favorable toward abortion requests than were high sex guilt students, but both groups were more favorable toward abortion when conception was the result of failure of a contraceptive method than when it was due to the applicant's inconsistent use of the method. In addition, high sex guilt students' abortion decisions were significantly influenced by the relationship of the applicant to her coital partner. When the relationship was “steady,” they approved the request, whereas abortion was denied to the applicant who conceived with a casual partner. The results were discussed within the context of the debate over the morality of abortion and the problem of unwanted adolescent pregnancy. It was suggested that sex guilt may play a larger role in these issues than has been previously recognized, and that presenting the “facts” (sexual knowledge) may have little impact in abortion related decisions.