A model of working memory capacity in the radial-arm maze task

The radial arm maze is one of the most commonly used tests for assessing working memory in laboratory animals. However, to date, there exists no quantitative method of estimating working memory capacity from performance on this task. Here, we present a mathematical model of performance on the radial arm maze from which we can derive estimates of capacity. We derive explicit results for the two most commonly used measures of performance as functions of number of arms in the maze and memory capacity, assuming a uniform random search. We simulate random non-uniform search strategies. Comparing our model to previous experiments, we show that our model predicts a working memory capacity in the range of 3-9 at the level of performance observed in these experiments. This estimate is within the typical estimate of human working memory capacity. Performance of rats on large mazes (e.g. 48 arms) has been used as evidence that the working memory capacity of rats may be significantly larger than that of humans. We report that memory capacity in the range 3-9 is sufficient to explain the performance of rats in very large radial mazes. Furthermore, when we simulate non-uniform random search strategies observed in the experiments, the resulting estimates do not differ significantly from those assuming a uniform random search. We conclude that a list-based model of working memory with modest capacity is more powerful than previously expected.     

Mixed effects modeling of Morris water maze data: Advantages and cautionary notes

Morris water maze data are most commonly analyzed using repeated measures analysis of variance in which daily test sessions are analyzed as an unordered categorical variable. This approach, however, may lack power, relies heavily on post hoc tests of daily performance that can complicate interpretation, and does not target the nonlinear trends evidenced in learning data. The present project used Monte Carlo simulation to compare the relative strengths of the traditional approach with both linear and nonlinear mixed effects modeling that identifies the learning function for each animal and condition. Both trend-based mixed effects modeling approaches showed much greater sensitivity to identifying real effects, and the nonlinear approach provided uniformly better fits of learning trends. The common practice of removing a rat from the maze after 90 s, however, proved more problematic for the nonlinear approach and produced an underestimate of y-axis intercepts.     

PHILOSOPHERS OF INTELLECTUAL DISABILITY: A TAXONOMY

Abstract: This essay explores various roles that philosophers occupy in relation to intellectual disability. In examining how philosophers define their object of inquiry as experts and gatekeepers, it raises critical questions concerning the nature of philosophical discourse about intellectual disability. It then goes on to consider three alternate positions, the advocate or friend, the animal, and the "intellectually disabled," each of which points to new ways of philosophizing in the face of intellectual disability.     

THE CAPABILITIES OF PEOPLE WITH COGNITIVE DISABILITIES

Abstract: People with cognitive disabilities are equal citizens, and law ought to show respect for them as full equals. To do so, law must provide such people with equal entitlements to medical care, housing, and other economic needs. But law must also go further, providing people with disabilities truly equal access to education, even when that is costly and involves considerable change in current methods of instruction. The central theme of this essay is what is required in order to give such people political and civil rights on a basis of genuine equality.     

THE ENTANGLEMENT OF RACE AND COGNITIVE DIS/ABILITY

Abstract: To consider blackness and cognitive disability together is paradoxical. On one hand, supposed black intellectual deficit has been used by white elites as a justification for antiblack oppression. On the other, both black children who are struggling in school and black adults labeled with developmental disabilities are less likely than their white counterparts to access the best support services available. These problems cut across a commonly drawn—but, I argue, erroneous—divide between the "judgment" categories of mild cognitive impairment into which black children are disproportionately placed and the "organic" categories of severe cognitive impairment. This division is itself part of the contemporary collective denial of the racialized history and construction of our notion of intellect that ends up harming black Americans.     

A Spirituality of the Desert for Education: The Call of Justice Beyond the Individual or Community

This paper argues for an alternative notion of spirituality for education, based on Theo de Boer’s idea of a spirituality of the desert. Rather than depicting an inner, additional region named the spiritual, spirituality here is thought of as a discourse that depicts the everyday world in a particular way. In dialogue with David Purpel’s analysis, the paper argues for a notion of spirituality that is located in an ongoing oscillation between ‘the individual’ and ‘the community.’ This oscillation turns out to be the call of justice. This analysis helps understand classroom dynamics differently, providing a place of critique for current practices.

The development of category learning strategies: What makes the difference?

Category learning can be achieved by identifying common features among category members, distinctive features among non-members, or both. These processes are psychologically and computationally distinct, and may have implications for the acquisition of categories at different hierarchical levels. The present study examines an account of children’s difficulty in acquiring categories at the subordinate level grounded on these distinct comparison processes. Adults and children performed category learning tasks in which they were exposed either to pairs of objects from the same novel category or pairs of objects from different categories. The objects were designed so that for each category learning task, two features determined category membership whereas two other features were task irrelevant. In the learning stage participants compared pairs of objects noted to be either from the same category or from different categories. Object pairs were chosen so that the objective amount of information provided to the participants was identical in the two learning conditions. We found that when presented only with object pairs noted to be from the same category, young children (6 ? YO ? 9.5) learned the novel categories just as well as older children (10 ? YO ? 14) and adults. However, when presented only with object pairs known to be from different categories, unlike older children and adults, young children failed to learn the novel categories. We discuss cognitive and computational factors that may give rise to this comparison bias, as well as its expected outcomes.     

Short-term gains, long-term pains: How cues about state aid learning in dynamic environments

Successful investors seeking returns, animals foraging for food, and pilots controlling aircraft all must take into account how their current decisions will impact their future standing. One challenge facing decision makers is that options that appear attractive in the short-term may not turn out best in the long run. In this paper, we explore human learning in a dynamic decision making task which places short- and long-term rewards in conflict. Our goal in these studies was to evaluate how people’s mental representation of a task affects their ability to discover an optimal decision strategy. We find that perceptual cues that readily align with the underlying state of the task environment help people overcome the impulsive appeal of short-term rewards. Our experimental manipulations, predictions, and analyses are motivated by current work in reinforcement learning which details how learners value delayed outcomes in sequential tasks and the importance that “state” identification plays in effective learning.     

Errors, efficiency, and the interplay between attention and category learning

Learning to identify objects as members of categories is an essential cognitive skill and learning to deploy attention effectively is a core component of that process. The present study investigated an assumption imbedded in formal models of categorization: error is necessary for attentional learning. Eye-trackers were used to record participants’ allocation of attention to task relevant and irrelevant features while learning a complex categorization task. It was found that participants optimized their fixation patterns in the absence of both performance errors and corrective external feedback. Optimization began immediately after each category was mastered and continued for many trials. These results demonstrate that error is neither necessary nor sufficient for all forms of attentional learning.     

Neonatal imitation in chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>) tested with two paradigms

Primate species differ in their imitative performance, perhaps reflecting differences in imitative capacity. The developmentally earliest form of imitation in humans, neonatal imitation, occurs in early interactions with social partners, and may be a more accurate index of innate capacity than imitation of actions on objects, which requires more cognitive ability. This study assessed imitative capacity in five neonatal chimpanzees, within a narrow age range (7–15 days of age), by testing responses to facial and vocal actions with two different test paradigms (structured and communicative). Imitation of mouth opening was found in both paradigms. In the communicative paradigm, significant agreement was found between infant actions and demonstrations. Additionally, chimpanzees matched the sequence of three actions of the TC model, but only on the second demonstration. Newborn chimpanzees matched more modeled actions in the communicative test than in the structured paradigm. These performances of chimpanzees, at birth, are in agreement with the literature, supporting a conclusion that imitative capacity is not unique to the human species. Developmental histories must be more fully considered in the cross-species study of imitation, as there is a greater degree of innate imitative capacity than previously known. Socialization practices interact with innate and developing competencies to determine the outcome of imitation tests later in life.