Causal Induction in the Presence of a Perfect Negative Cue: Contrasting Predictions from Associative and Statistical Models

Two experiments on human causal induction with multiple candidate causes are reported. Experiment 1 investigated the influence of a perfect preventive cause on the ratings of a less contingent cause. Whereas the Rescorla-Wagner model (RWM) and Cheng's probabilistic contrast model predict that the less contingent cause should be completely discounted, the Pearce model predicts, in most cases, an enhancement of that cause's perceived importance. Results corresponded more closely tothe predictions of the Pearce model.The predictions of both the RWM and the Pearce model rely on a constant context cue acquiring associative strength, yet no such cue was explicitly identified in the task scenario employed in Experiment 1. Experiment 2 replicated a number of key conditions of Experiment 1 with a task scenario that afforded ratings of the causal importance of the context in which the effectiveness of the discrete candidate causes was evaluated. In addition, the number of trials was increased to test the possibility that the ratings in Experiment 1 were the product of incomplete learning. The results of the first experiment were replicated and the ratings of the effectiveness of the context cue were anticipated by both the RWM and the Pearce model. Overall, the Pearce model offers a more comprehensive account of the causal inferences recorded in this study.     

The Effects of Prior Processing Episodes on Basic level Superiority

Four experiments were conducted to investigate the effects of prior processing episodes on people's preference for categorizing objects at the basic level (e.g. dog) relative to their preference for categorizing at the superordinate (e.g. animal) and the subordinate (e.g. Dalmation) levels. The prior processing episode in Experiment 1 was designed to induce subjects to activate representations at the superordinate level, and those in the remaining experiments were designed to induce subjects to differentiate objects at the subordinate level. After the prior processing episodes, subjects performed either a free naming or a picture categorization task that required them to decide whether an illustrated object belonged to a specified category. Results showed that prior processing episodes modestly reduced the superiority of basic level to superordinate level and subordinate level in categorization but not in free naming. The results suggest that the basic-level advantage is subject to the effects of context, but the effects are not as strong as the context effects on other aspects of categorization behaviour (e.g. rating typicality of a category member). Hence, the preference for the basic level is a somewhat more stable, invariant aspect of conceptual representation. Possible determinations of this stability are discussed.     

High calcium intake does not prevent stress-salt hypertension in dogs

Avoidance conditioning sessions and isotonic saline (1.3 L/day) were administered to dogs for 12 days under conditions of a low (0.1%) or high (1.5%) calcium diet. Twenty-four-hour mean arterial pressure increased comparably during the stress-salt conditioning periods on both the low (systolic: +16 ± 5 mm Hg; diastolic: +6 ± 2 mm Hg) and high (systolic: +17 ± 4 mm Hg; diastolic: +11 ± 4 mm Hg) calcium diets. Urine volume, sodium excretion, and serum calcium levels on the high calcium diet were not significantly different from those on the low calcium diet. In a second experiment, calcium was infused continuously for six days into the arterial circulation of normotensive or stress-salt hypertensive dogs at a rate of 0.12–0.23 mEq/min. Although serum calcium levels increased by up to 50% under these conditions, there were no significant effects on 24-hour levels of arterial pressure. In contrast to the protective effect of augmented potassium intake, these findings indicate that calcium intake does not influence the development of stress-salt hypertension in dogs.     

Self-monitoring and age

Two adult samples were surveyed to investigate the relation between individuals' levels of self-monitoring and age. A negative relation was predicted as older individuals were seen as most likely to exhibit the low self-monitoring tendency of behaving in accordance with one's own attitudes and feelings, whereas younger individuals appeared most likely to exhibit the high self-monitoring tendency of behaving according to social cues. A significant negative correlation between age and self-monitoring was found in both samples. The self-monitoring construct is discussed in relation to other social-cognitive life-span differences and to the idea of critical periods throughout the life span.     

Social facilitation and inhibition of emotional expression and communication.

Does the presence of others facilitate or inhibit emotional expression? Female "senders" (n = 45) viewed 12 emotionally loaded slides either alone or with another sender while responses were secretly videotaped. In Study 1, 14 "receivers" guessed the type of slide viewed by dyads more accurately (eta = .366). In Study 2, 42 receivers viewed 10 senders with friends, 10 with strangers, and 10 alone. One dyad member was covered so that only 1 sender was visible. Analysis revealed significant effects of condition (alone, friend, or stranger; eta = .456), slide type (sexual, scenic, unpleasant, or unusual; eta = .325), and the Condition x Slide Type interaction (eta = .350). Strangers had overall inhibitory effects on communication accuracy, whereas friends had facilitative effects on some slides and inhibitory effects on others. Thus, both social facilitation and inhibition of expression occurred on the basis of the emotional stimulus and personal relationship involved.     

Induction and category coherence

In studies of category formation, subjects rarely construct family resemblance categories. Instead, they divide objects into categories using a single dimension. This is a puzzling result given the widely accepted view that natural categories are organized in terms of a family resemblance principle. The observation that natural categories support inductive inferences is used here to test the hypothesis that family resemblance categories would be constructed if stimuli were first used to generate inductive inferences. In two experiments, subjects answered either induction questions, which made interproperty relationships more salient, or frequency questions, which required information only about individual properties, before they performed a sorting task. Subjects were likely to produce family resemblance sorts if they had first answered induction questions but not if they had answered frequency questions.     

Heart rate during group flooding therapy for PTSD

The objective of this study was to assess, via heart rate, the arousal levels of participants in group trauma reexposure therapy for posttraumatic stress disorder, and so to better understand this common mode of treatment, particularly in regards to its presumed curative factor, extinction. Six Vietnam combat-related PTSD inpatients participated twice weekly in group trauma reexposure therapy during which their electrocardiograms were recorded. Heart rate was quantified continuously off-line. Heart rates of participantsnot directly engaged in imaginal reexposure to their personal combat traumas consistently exhibited mild linear declines from the beginnings to the ends of the approximately 2.5 hour sessions. Participants actively engaged in personal combat trauma reexposure exhibited higher whole-session heart rates. Most also exhibited more specific elevation extending over the later portions of therapy sessions during which intensive reexposure usually occurred. Surprisingly, no patients exhibitedfocal increases in heart rate concurrent with periods of most intensive traumatic incident review as judged from videotape. Administering imaginal reexposure in a group context does not preclude substantial physiological (sympathetic) arousal, as is preconditional for extinction. Under conditions in which the actively engaged reexposure patient is reliably identified, group trauma reexposure therapy may not provide an opportunity for “vicarious” flooding in nonengaged participants.