Electrodermal activity and extraversion: Caffeine,preparatory signal and stimulus intensity effects

The Eysenck hypothesis that introverts are more and extraverts less cortically aroused has been supported by the results of most electrodermal studies, though there is some inconsistency in the literature. Further tests of the hypothesis can be carried out using arousal-manipulation paradigms. Some studies have used caffeine or stimulus intensity to increase arousal, as was also the case in the present study. The latter, however, also introduced a preparatory signal, which may be expected under certain conditions, to reduce responses to the stimulus which follows it. Extraverts and introverts were randomly assigned to receive low, medium or high doses of caffeine or a placebo. Each S then heard two sets of tones with the tones in one set preceded by a preparatory signal. Results showed that the preparatory signal reduced phasic amplitudes only at the highest levels of stimulus intensity. Introverts had higher overall SCLs and response magnitudes. In addition, the preparatory signal had little effect on extraverts, but reversed dosage-related response patterns in introverts. Results were supportive of the basic Eysenck arousal hypothesis and also showed that the arousal difference leads to attentional variability between the two groups.     

Analysis of treatments to alleviate forgetting in rats

Two experiments with rats investigated the effectiveness of prior-cuing treatments for alleviating forgetting of aversive conditioning. The aim was to see which retrieval cues would be most effective within different contexts. Experiment 1 examined the contexts of classical fear conditioning and instrumental avoidance training. The results indicated that the response components were sufficient to reinstate avoidance training, whereas the unconditioned stimulus (US) was most effective for classical fear conditioning. In Experiment 1, the reinforcer per se was ineffective in reinstating instrumental avoidance training. Experiment 2 manipulated the training context and found that the US could be made an effective prior-cuing treatment for instrumental training if classical conditioning components were more prevalent during training. These results are interpreted to mean that a "critical context" must be reinstated by the cuing treatment if this treatment is to promote retrieval of the memory.     

Ontogeny of cholinergic mediation of behaviors in the rat.

In a series of six experiments, cholinergic mediation of behavior was studied in immature rats. It was found that although scopolamine disrupted discriminative choice behavior in both 15- and 23-day-old rat pups, it increased latency to choice in 15-day-olds and decreased latency to choice in 23-day-olds. This disruption of discriminated choice behavior was not due to differential shock thresholds or differences in locomotor activity between drug-treated and control animals, nor was it specific to a T-maze shock-escape discrimination task. These results suggest that central cholinergic mediation of different behaviors may mature at different rates.     

Relationship between sex, age, education and field-dependence: a cross-cultural comparison

Past examination of the relationship between field-independence and age has indicated a developmental trend of increased field-independence up to 17 yr., with a movement toward greater field-dependence after this point. However, discrepancies between longitudinal and cross-sectional findings suggest that this relationship may be confounded by socioeconomic variables. The present study examined the age/field-dependence relationship in a sample of Northern Italians controlling for educational background. Results for females indicated statistical control of educational variables modified the age/field-dependence relationship, but did not for the male sample.     

Levels of experienced dimensionality in children and adults

This work presents a new conceptualization of the contrast between holistic and differentiated perception of multidimensional stimuli. Specifically, two hypotheses about the experiential status of dimensions within holistic perception are proposed and tested as explanations of young children's general perceptual mode and adults' integral mode. The major result is that three levels of dimensional status are realized: (1) the hypothesis of nonprimary axes characterizes adult “integral” perception of saturation and brightness relations, (2) the hypothesis of primary but not mandatory axes characterizes kindergarteners' “integral” perception of size and shade relations, and (3) the notion of mandatory axes characterizes adults' separable perception of size and shade relations. These results indicate a new interpretation of the integrality-separability distinction and the derivative developmental hypothesis. It is specifically hypothesized that the developmental history of most dimensional combinations includes these three levels.     

Effects of 6-hydroxydopamine lesions of the nucleus accumbens septi and olfactory tubercle on feeding, locomotor activity, and amphetamine anorexia in the rat.

Bilateral 6-hydroxydopamine lesions of the nucleus accumbens septi (NAS) and olfactory tubercle (OT) caused enhanced intake of wet mash in 23-hr-food-deprived rats tested in photocell activity cages during restricted 30-min sessions. This mild hyperphagia was accompanied by a significant hypoactivity in the group with NAS/OT lesions. No hyperphagia was observed during a prolonged 120-min test session or in free-feeding tests conducted in the home cage. Anorexia induced by d-amphetamine (.5 and 1.5 mg/kg) was unaltered by the lesion, although the locomotor stimulant action of the drug was attenuated. A second experiment showed that the NAS/OT lesion also enhanced food intake in the photocell cages during 30-min sessions with dry food pellets but that food-associated drinking was concomitantly reduced. The results are consistent with the hypothesis that the behavioral changes caused by mesolimbic neuron destruction result in part from an inability to switch from one behavioral activity to another.     

Is there a developmental trend from integrality to separability in perception?

Some previous literature suggests that young children perceive in an integral, holistic fashion stimuli that older children perceive in a separable, dimensionalized mode. A prediction from a strong form of this position is that younger children actually may perform more rapidly a speeded classification task that requires “condensation” than a task that requires “filtering” (if the similarity relations among the wholes favor the former task). Older children should be able to take advantage of the simple unidimensional basis of the filtering task and thus accomplish it much more rapidly than the condensation task. The results are only partially in accord with the predictions. Kindergarteners (5 years of age), on size-and-brightness stimuli, show no speed advantage on either task, while second (8 years) and fifth (11 years) graders clearly show more rapid filtering. Therefore, the developmental hypothesis is in need of some revision and elaboration. Some stimuli are less separable for younger than for older children, but even five year olds can access their dimensional structure under some conditions.     

The genesis and use of exemplar vs. prototype knowledge in abstract category learning

Accurate classification of new exemplars in an abstraction paradigm may be due to their similarity to old exemplars rather than to abstract category (or prototype) knowledge. In the present study, subjects received initial training on a two-category problem before being transferred to a task in which half of the exemplar-response pairs had their responses reversed while the remaining half of the pairs were unchanged. When transfer occurred with no delay and involved old exemplars, more errors occurred for changed than for unchanged pairs. This result implies the use of exemplar-specific rather than abstract category knowledge. However, when transfer was delayed by 24 or 72 h, errors occurred equally often for changed and unchanged pairs. This result suggests that exemplar-specific knowledge is no longer used. Since subjects were still able to accurately classify exemplars prior to the transfer task at these delays, some form of abstract category knowledge is implicated.