Learning and transfer from a simple dynamic system

The amount of learning gained from being assisted in completing the task of bringing a predator-prey system into equilibrium by controlling the predator population was investigated. Learning was explored both by post-task questioning and by testing for transfer to another predator-prey task. Participants were 28 undergraduate psychology students, all female. They were randomly and evenly split into an experiment group that was subjected to a learning session with the first task before being tested in the second task, and a control group that only performed the second task. What was most needed in the first task was help in sticking to analytically derived conclusions by resisting "common sense" responses. There was a significant transfer effect on performance to the second task, stemming from learning shown by half the participants in the experiment group. The other half showed hardly any learning. Learning in about half the subjects has proven a stable finding.     

Hypnosis and clinical pain

Hypnosis has been demonstrated to reduce analogue pain, and studies on the mechanisms of laboratory pain reduction have provided useful applications to clinical populations. Studies showing central nervous system activity during hypnotic procedures offer preliminary information concerning possible physiological mechanisms of hypnotic analgesia. Randomized controlled studies with clinical populations indicate that hypnosis has a reliable and significant impact on acute procedural pain and chronic pain conditions. Methodological issues of this body of research are discussed, as are methods to better integrate hypnosis into comprehensive pain treatment.     

Relation of Age of Onset to the Type and Severity of Child and Adolescent Conduct Problems

In a cross-sectional household sample of 9-through 17-year-old youths from 4 U.S. communities, youths with earlier ages of onset of conduct problems engaged in more conduct problems than youths with later ages of onset when current age and gender were controlled. Specifically, youths with earlier ages of onset were more likely to engage in several types of physical aggression, frequent lying, theft, and vandalism and were less likely to engage in only truancy. There also was an inverse relation between age of onset and level of functional impairment, mental health service use, and meeting diagnostic criteria for conduct disorder, attention-deficit hyperactivity disorder, and oppositional defiant disorder. Within the limits of cross-sectional data, these results support the hypothesis that key aspects of the heterogeneity of conduct problems among youths are related to the age of onset of conduct problems.     

Posttraining Electrical Stimulation of Vagal Afferents with Concomitant Vagal Efferent Inactivation Enhances Memory Storage Processes in the Rat

Peripherally administered or released substances that modulate memory storage, but do not freely enter the brain, may produce their effects on memory by activating peripheral receptors that send messages centrally through the vagus nerve. Indeed, vagus nerve stimulation enhances memory performance, although it is unclear whether this effect is due to the activation of vagal afferents or efferents. To eliminate the possible influence of descending fibers on memory storage processes, rats were implanted with cuff electrode/catheter systems along the left cervical vagus. Forty-eight hours following surgery, each animal received a 3.0-μl infusion (1.0 μl/min) of either lidocaine hydrochloride (75.0 mM) or isotonic saline below the point of stimulation. Animals were then trained 10 min later on an inhibitory-avoidance task with a 0.75-mA, 1.0-s foot shock. Sham stimulation or vagus nerve stimulation (0.5-ms biphasic pulses; 20.0 Hz; 30 s; 0.2, 0.4, or 0.8 mA) was administered immediately after training. Memory, tested 24 h later, was enhanced by stimulation whether descending vagus nerve fibers were inactivated or not. Both lidocaine- and saline-infused groups showed an intensity-dependent, inverted-U-shaped pattern of retention performance, with the greatest effect observed for 0.4 mA (U= 9,p< .05, andU= 7,p< .01, respectively). Additionally, animals that received lidocaine infusions, but no vagus nerve stimulation, showed impaired memory compared to the performance of saline-infused control animals (U= 11,p< .05). Together, these findings suggest that vagal afferents carry messages about peripheral states that lead to the modulation of memory storage and that the memory-enhancing effect produced by vagus nerve stimulation is not mediated via the activation of vagal efferents.     

From individual to group impressions: Availability heuristics in stereotype formation

When subjects are presented with information about the attributes of individuals and are then asked to make judgments about the characteristics of the group composed of those individuals, the group impression may depend on the way in which data on individuals are organized in memory. Experiment 1 demonstrated that under conditions of low memory load (16 instances of person-trait pairings), subjects organize their perceptions of a group around the characteristics of its individual members, whereas under high memory load (64 instances of person-trait pairings), subjects organize trait information in an undifferentiated way around the group as a whole. Under low memory load, subjects distinguish between repeated occurrences of a trait in the same individual and comparable repeated occurrences of that trait in different individuals; under high memory load, subjects do not make such a differentiation. Subjects' judgments about the frequency of categories of traits were related to the ease of recall of category instances, as predicted by an availability heuristic. Experiments 2 and 3 demonstrated that group members who are most available in memory will be disproportionately represented in the group impression. Specifically, the proportion of extreme individuals in a group was retro-spectively overestimated; this was true for both physical stimuli (height) and social stimuli (criminal acts).     

Ten-year follow-up of a successful treatment of self-injurious behavior

Ten years ago, self-injurious behavior that produced blindness in a man with profound mental retardation was treated through behavioral intervention. This person's behavioral history was reviewed for 12 years prior to the intervention through examination of his clinical record and for 10 years following the intervention through examination of his clinical record, direct observation, and interviews with staff. Physical injury occurred only once in the last 46 months; physical restraint has not been used in 10 years; and for the past 9 years, no more than one medication has been prescribed for the control of behavior or seizures. Suggestions are presented for designing behavioral interventions at the beginning of treatment to maintain reductions in behavior.     

The effects of family structure on the sexual behavior of adolescents.

The effects of two family structures, single- and two-parent homes, on adolescent sexual behavior were studied. The variables of race, age, and gender were controlled. The analysis compared the age at first intercourse, frequency of intercourse in the last four weeks, and virgin/nonvirgin status of adolescents from black single-parent families, white single-parent families, black two-parent families, and white two-parent families. For males, the two-parent family was related to less sexual activity and older age at first intercourse. For females, the two-parent family was not as important as race in influencing sexual behavior. The white females from two-parent families were more likely to be virgins, but once having had sexual intercourse, tended to have a higher level of sexual activity than did black females from two-parent homes.     

Adolescent sexuality and public policy

In recent decades, various attempts have been made to determine the level of sexual activity among adolescents. This information has been used in the planning and evaluation of sex-related programs. However, there is a flaw in using only the initial estimates of the behavior--that a sexually active person is defined as one who has had sexual intercourse. This narrow definition distorts the perception of adolescent sexual behavior. Sexual activity can more accurately be designated by focusing on the actual frequency with which teenagers have sex. In this research report, adolescents were considered sexually active if they had had sex within the last four weeks. Using this definition, adolescents were found to be substantially less sexually active than has been previously reported. This finding was then used to look at various policy decisions in the areas of sex education, family planning, and sexually transmitted disease prevention.