Memory storage and retrieval processes in category learning

The detailed course of learning is studied for categorization tasks defined by independent or contingent probability distributions over the features of category exemplars. College-age subjects viewed sequences of bar charts that simulated symptom patterns and responded to each chart with a recognition and a categorization judgment. Fuzzy, probabilistically defined categories were learned relatively rapidly when individual features were correlated with category assignment, more slowly when only patterns carried category information. Limits of performance were suboptimal, evidently because of capacity limitations on judgmental processes as well as limitations on memory. Categorization proved systematically related to feature and exemplar probabilities, under different circumstances, and to similarity among exemplars of categories. Unique retrieval cues for exemplar patterns facilitated recognition but entered into categorization only at retention intervals within the range of short-term memory. The findings are interpreted within the framework of a general array model that yields both exemplar-similarity and feature-frequency models as special cases and provides quantitative accounts of the course of learning in each of the categorization tasks studied.     

Visual control of step length during running over irregular terrain

Running over uneven ground requires visually regulating step length to secure proper footing. To examine how this is achieved, we studied subjects running on a treadmill on a series of irregularly spaced targets. The movements of their lower limbs and coccyx relative to the targets were monitored opto-electronically by a Selspot system. The results indicated that step length was adjusted to strike the targets primarily by varying the vertical component of impulse applied to the ground during the stance phase. In contrast, horizontal impulse was not varied significantly, and changing the reach forward of the foot on landing contributed little to variation in step length. Changing the vertical impulse simply altered the step time proportionately. Thus the data are consistent with a time-based model in which vertical impulse is modulated by the optic variable delta tau (Lee, 1976) specifying the time gap that has to be bridged by the runner between two targets.     

Multidimensional scaling reveals two dimensions of thermal pain

The Individual Differences Scaling (INDSCAL) model of multidimensional scaling was used to explore the dimensions of thermal pain. The observers made 66 similarity judgments to all pairs of 12 different thermal stimulus intensities ranging from zero to noxious. Analysis of the data revealed a two-dimensional group stimulus space. The major dimension ordered the stimuli with respect to their intensity. This quantitative, strength-of-sensation dimension may be interpreted as indicating how weak or strong a stimulus feels, apart from any secondary qualities of warmth or pain. The second dimension was related to the qualitative aspects of the stimuli. This bipolar dimension contained two attributes: a pain attribute ranging from just detectable warmth to painful, and a warm-hot attribute running from just detectable warmth to hot. This study demonstrates the utility of the INDSCAL approach to the understanding of pain and offers a new technique for answering the age-old question concerning the number and qualities of the dimensions underlying the pain experience.     

Glucose effects on memory: behavioral and pharmacological characteristics

Recent findings indicate that post-training glucose injections can modulate memory storage for inhibitory (passive) avoidance training. Experiment I extended these findings to determine whether glucose, like other memory modulating treatments, enhances memory storage when administered after training with low footshock and impairs memory storage after high footshock training. In Experiment I, male Sprague-Dawley rats were trained in a one-trial inhibitory avoidance task using either a brief footshock (0.5 mA, 0.7 s) or slightly more intense footshock kept on until escape (0.7 mA, mean escape latency = 3.4 s). Immediately after training, each rat received a subcutaneous injection of glucose (100 mg/kg). When tested for retention performance 24 h later, the glucose-injected animals exhibited enhanced retention performance for low footshock training and impaired retention for high footshock training. Experiment II determined whether pretreatment with adrenergic antagonists blocked the effects of glucose on memory. Pretreatment with the alpha- or beta-adrenergic receptor antagonists, phenoxybenzamine, or propranolol, respectively, had no effect on acquisition or retention in animals trained with the brief footshock and did not affect glucose facilitation of that memory. In animals trained to escape footshock, phenoxybenzamine did not attenuate the amnesia produced by glucose. Propranolol-pretreated animals had impaired retention whether or not they received post-training amnestic injections of glucose; glucose had no effect on retention in these amnestic animals. These findings add further support to the view that glucose release after training and treatment may represent a physiological response subsequent to epinephrine release in modulating memory storage processing.     

Sex differences in the effects of gonadectomy on amphetamine-induced rotational behavior in rats

The effects of gonadectomy on amphetamine-induced rotational behavior were studied in male and female rats. Different systemic doses were used to produce equivalent brain concentrations of the drug in each group, thereby controlling for sex differences in the metabolism of amphetamine. Ovariectomy of female rats significantly attenuated amphetamine-induced rotation, whereas castration of males was without effect. The results support the idea that in females, the endogenous gonadal hormones facilitate functional activity in the mesostriatal dopamine system.     

Glucose modulation of memory storage processing

Epinephrine, derived from the adrenal medulla, enhances memory storage for several forms of learning. One physiological action of this hormone is to liberate hepatic glucose stores. This experiment tested the possibility that glucose could itself enhance memory. Rats were water deprived, pretrained to drink, pretrained to drink in the behavioral apparatus, and then trained in a one-trial inhibitory (passive) avoidance task. Immediately after the training footshock, the animals each received an injection of glucose (1.0-500 mg/kg). When tested for retention 24 h later, the animals which received 10 or 100 mg/kg doses of glucose exhibited enhanced retention performance; higher and lower doses had no significant effect on the memory tests. Also, glucose injections (100 mg/kg) delayed by 1 h after training had no effect on the retention tests. These findings suggest that the increase in plasma glucose levels subsequent to epinephrine injection may contribute to the effects of epinephrine on memory. In addition, the results suggest that peripheral glucose levels may exert important influences on memory storage.     

An evaluation of the family adaptability and cohesion evaluation scales and the circumplex model

Two basic assumptions of the Circumplex Model of family systems were evaluated: (1) Healthy families evidence balanced degrees of cohesion and adaptability, whereas problem families evidence extreme degrees, and (2) families with balanced degrees of cohesion and adaptability possess more positive communication skills than families with extreme degrees. Subjects were 58 mother-son dyads from father-absent families. In 29 of the families the adolescent was a juvenile offender, while in the remaining families there was no history of arrest or psychiatric referral. The dyads completed the Family Adaptability and Cohesion Scales (FACES) and an unrevealed differences interaction task. FACES was highly proficient at differentiating delinquent from nondelinquent families. Moreover, in families with balanced degrees of cohesion and adaptability, the mothers' communication was significantly more supportive and explicit, and the dyads evidenced significantly greater warmth and affection than dyads with extreme degrees.This research was supported by funding to the Department of Psychology at Memphis State University granted through the Centers of Excellence Program of the State of Tennessee. We thank the staff of the Memphis-Metro Youth Diversion Project for their consideration and assistance.     

Health as a value: methodological and theoretical considerations

The concept of value placed on health is very important in several different theoretical approaches to the study of health behavior. In practice, however, health value is generally assumed to be universally high rather than being directly measured. If this assumption is incorrect, then theories that include health value have rarely been adequately tested. This paper presents a short 4-item Likert scale designed to measure the value placed on health. Norms from the utilization of this scale in five different samples are presented. Health value is found to increase with age among girls, but the increase apparently stops by late adolescence, before full adult levels of health value are achieved. Middle-aged women place a higher value on health than do middle-aged men, although no comparable sex difference appears in a sample of undergraduates. Consistent with theoretical predictions, both health locus of control beliefs and beliefs in the efficacy of certain preventive health behaviors correlate more highly with the performance of those same behaviors 5 to 9 months later among respondents who place a high value of health relative to those who do not value health so highly. However, this interaction is found only when it can be safely assumed that health is the primary value underlying the behavior. The importance of considering a variety of values in addition to health as possible motivators of preventive health behavior is stressed.     

Counseling Clients with AIDS

The authors discuss issues and suggestions relative to counseling clients with AIDS. Several psychosocial issues are presented, and a psycho-educational model of treatment to meet the needs of AIDS clients is described.