Why Higher Working Memory Capacity May Help You Learn: Sampling,Search, and Degrees of Approximation

Algorithms for approximate Bayesian inference, such as those based on sampling (i.e., Monte Carlo methods), provide a natural source of models of how people may deal with uncertainty with limited cognitive resources. Here, we consider the idea that individual differences in working memory capacity (WMC) may be usefully modeled in terms of the number of samples, or “particles,” available to perform inference. To test this idea, we focus on two recent experiments that report positive associations between WMC and two distinct aspects of categorization performance: the ability to learn novel categories, and the ability to switch between different categorization strategies (“knowledge restructuring”). In favor of the idea of modeling WMC as a number of particles, we show that a single model can reproduce both experimental results by varying the number of particles—increasing the number of particles leads to both faster category learning and improved strategy‐switching. Furthermore, when we fit the model to individual participants, we found a positive association between WMC and best‐fit number of particles for strategy switching. However, no association between WMC and best‐fit number of particles was found for category learning. These results are discussed in the context of the general challenge of disentangling the contributions of different potential sources of behavioral variability.     

Varying reinforcement magnitude on interval schedules

In Experiment 1, rats were trained on either a random-interval or a variable-interval 60-sec schedule of reinforcement, and reinforcement magnitude was varied across conditions between one and four pellets. Although the two schedules maintained different patterns of behaviour, patterns and rates of responding were not systematically affected by the variation in reinforcement magnitude. In Experiment 2, a regulated probability interval schedule that generated similar rates of reinforcement to those of the schedules of Experiment 1 was used, with the pattern of behaviour generated resembling that typical of a random-interval schedule. Changing reinforcement magnitude again produced few systematic changes in behaviour. In Experiment 3, a variable-ratio schedule was used within a procedure that otherwise resembled that of Experiments 1 and 2. Increasing the reinforcement magnitude now decreased the rates of responding, and examination of the patterns of responding showed that this came about because rates of responding were higher early in the interreinforcer interval in the one-pellet condition. These experiments demonstrate the insensitivity of behaviour under interval schedules to changes in reinforcement magnitude and suggest the operation of mechanisms different from those engaged by ratio schedules and discretetrial learning procedures.     

The Trouble with Neurobiological Explanations of Mind

Neuroist literature dresses psychological narratives up with neuroscience facts. But there are fundamental differences between the languages of the mind and the brain, so ad hoc devices paper over the gaps. These include taking words out of their proper contexts; equating the conceptual architecture of psychology with the neural architecture of the brain; mimicking the format of scientific research papers; and exalting paradox to produce a thrilling sense of mystery. In addition there are outright errors that are hard for nonneuroscientists to detect. Neuroism is a bid for status by nonnatural science disciplines such as psychoanalysis.     

Differential Diagnosis of the Major Progressive Dementias and Depression in Middle and Late Adulthood: A Summary of the Literature of the Early 1990s

There is a preponderance of research on the neuropsychology of the various dementias. There are also direct comparisons between two or more dementias available in the literature. This paper sought to summarize the most recent literature, primarily from 1990 through mid-1996, including recent reviews of the literature from previous decades. The purpose was to provide, in one location, a summary of neuropsychological (i.e., cognitive, motor, and psychiatric) characteristics of major noninfectious, progressive dementias and depression of middle and late adulthood. It is hoped that this review, particularly a summary table provided, will serve as a guide in the differential diagnosis of the dementias by clinicians. In addition to Alzheimer's disease, vascular dementias, Parkinson's disease, Lewy body dementia, Huntington's disease, and frontal lobe dementia, the impact of depression on cognitive functioning is covered given the frequency with which neuropsychologists are asked to differentiate depression from primary dementia.     

An Assessment of Ethnocultural Beliefs Regarding the Causes of Birth Defects and Genetic Disorders

With the expansion of genetic services to various cultural groups, genetic counselors encounter clients who hold diverse beliefs inscribed by their culture about health conditions. Thus, clients may attribute the cause of a birth defect or genetic condition to a culturally-based health belief. This present study was conducted as a pilot study in order to assess the beliefs about the causes of birth defects and genetic disorders held by women of different ethnocultural backgrounds. This study proposed that women who do not have a family history of a disorder will differ in their knowledge about the cause of a birth defect or genetic disorder compared to women who have an affected child. In addition, this study determined to what extent culturally-based health beliefs are attributed to being the cause of a birth defect or genetic disorder in the 1990s.     

Visual attention in infants with perinatal brain damage: Evidence of the importance of anterior lesions

Shifts of visual attention can be studied in adults and infants by cueing responses to a particular spatial location. Earlier studies have shown that by seven months of age normal infants show a similar pattern of facilitation and inhibition to a cued spatial location as adults. In this study we report data from infants with perinatal lesions that include or exclude the left anterior quadrant. Results indicate that infants with left anterior lesions do not show facilitation to a cued spatial location in this task. In contrast, infants with posterior lesions showed the same pattern of performance as healthy subjects. While these findings differ from those obtained with adults, they are consistent with previous studies of children with perinatal lesions, and with findings from ERP studies with normal infants.