A comparative investigation of integral- and separable-dimension stimulus-sorting behavior.

Studies focusing on unsupervised categorization and sorting behavior have traditionally identified and empirically isolated a few select strategies frequently employed by observers, one-dimensional (SD), family resemblance (FR), and exclusive-or (XOR). To date, these investigations have mostly involved creating sets of multidimensional stimuli that directly contrast utilization of these strategies coupled with task or stimulus property manipulations to see their effects on categorization and sorting behavior. Currently, we extend on this methodological approach by having observers sort integral-dimension stimuli for two recently developed constrained unsupervised categorization tasks employing three-dimensional Boolean category structures. These structures instantiate six different sorting strategies, including the aforementioned SD, FR, and XOR strategies. Additionally, we connect the prevalence of the strategies observed across both tasks to previous investigations employing separable stimuli with the same tasks and underlying Boolean category structures. In comparison, our results indicate significant reductions in rule-like sorting behavior (SD or XOR) across multiple structures with the integral stimuli. Associated with this decrease in SD and XOR behavior was a corresponding increase in FR and FR-related sorting behavior. Finally, we assess how well generalized representational information theory and the simplicity model can account for the pattern of results across both experimental paradigms and stimulus sets. In general, a formal model derived from "GRIT" outperforms the simplicity model, accounting for nearly the entire range of unsupervised sorting behavior (SD, FR, XOR) observed across the separable and integral tasks.

Context, structure, and informativeness judgments: An extensive empirical investigation.

We explored the nature of human informativeness judgments: namely, people's judgments about the quantity of information that object stimuli convey about the category of objects to which they belong. Informativeness judgments play a key role in everyday decision-making situations involving the selection of items from groups that best represent the "group as a whole." They also provide insight into the nature of prototype formation. We investigated informativeness judgments with an experiment involving 41 category structures - the most comprehensive and rigorous examination thus far. We assess the robustness and generalizability of the results from this experiment by examining the relationship between group-level and individual-level performance. In addition, we show that in most cases (and especially in those involving relatively lower dimensionality structures), these judgments are predicted more accurately and explained more satisfactorily by Representational Information Theory (Vigo in Information Sciences 181: 4847-4859, 2011 and in Information 4(1):1-30, 2012) and its simplest core model than by standard models of prototypicality. Finally, we argue that prototypicality models are special cases of the more general "representational information" framework.

On the learning difficulty of visual and auditory modal concepts: Evidence for a single processing system.

The logic operators (e.g., "and," "or," "if, then") play a fundamental role in concept formation, syntactic construction, semantic expression, and deductive reasoning. In spite of this very general and basic role, there are relatively few studies in the literature that focus on their conceptual nature. In the current investigation, we examine, for the first time, the learning difficulty experienced by observers in classifying members belonging to these primitive "modal concepts" instantiated with sets of acoustic and visual stimuli. We report results from two categorization experiments that suggest the acquisition of acoustic and visual modal concepts is achieved by the same general cognitive mechanism. Additionally, we attempt to account for these results with two models of concept learning difficulty: the generalized invariance structure theory model (Vigo in Cognition 129(1):138-162, 2013, Mathematical principles of human conceptual behavior, Routledge, New York, 2014) and the generalized context model (Nosofsky in J Exp Psychol Learn Mem Cogn 10(1):104-114, 1984, J Exp Psychol 115(1):39-57, 1986).

Classification of three-dimensional integral stimuli: Accounting for a replication and extension of Nosofsky and Palmeri (1996) with a dual discrimination invariance model.

The quest for determining the degree of learning difficulty associated with different types of categories has been instrumental in our understanding of human categorization behavior and, more broadly, human generalization. For instance, we now know that the topological nature of the dimensions (e.g., whether these are integral or separable) that define the family of categories generated with three binary dimensions yield two different learning difficulty orderings. In our study, for the first time, we replicated one such classic ordering involving integral dimensions and explored the impact that the choice of dimensional values, along with the nature of the stimulus presentation, had on learning difficulty during the learning phase of our four experiments. Two standard orderings were observed in our investigation which were consistent with the hypothesis that multilevel discrimination plays a key role in concept learning. We accounted for our empirical results by making this role explicit at three levels, the feature, object, and category structure levels, using a dual discrimination invariance model (DDIM) derived from the core invariance law of generalized invariance structure theory (GIST). The model involves a "discrimination switch" via what is referred to in GIST as the "tau discrimination threshold" where two distinct extreme degrees of discrimination yield two fundamental learning difficulty orderings able to account for results from our experiments without free parameters. We then show how the DDIM is not only a more accurate and general predictor than the best alternatives but also provides a plausible and tenable cognitive mechanism for understanding these behaviors. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Constructing and Deconstructing Concepts.

Several empirical investigations have explored whether observers prefer to sort sets of multidimensional stimuli into groups by employing one-dimensional or family-resemblance strategies. Although one-dimensional sorting strategies have been the prevalent finding for these unsupervised classification paradigms, several researchers have provided evidence that the choice of strategy may depend on the particular demands of the task. To account for this disparity, we propose that observers extract relational patterns from stimulus sets that facilitate the development of optimal classification strategies for relegating category membership. We conducted a novel constrained categorization experiment to empirically test this hypothesis by instructing participants to either add or remove objects from presented categorical stimuli. We employed generalized representational information theory (GRIT; Vigo, 2011b , 2013a , 2014 ) and its associated formal models to predict and explain how human beings chose to modify these categorical stimuli. Additionally, we compared model performance to predictions made by a leading prototypicality measure in the literature.

Pentostatin in the treatment of hairy-cell leukemia.

Pentostatin (2'-deoxycoformycin; Nipent), a potent inhibitor of adenosine deaminase, is a purine nucleoside analogue that is highly effective in the treatment of hairy-cell leukemia. This agent is capable of inducing durable complete remissions in the majority of patients, and is capable of re-inducing a complete remission in many of the patients who have relapsed. Pentostatin appears to have changed the natural history of this disease. Long-term follow-up studies suggest that patients with hairy-cell leukemia who are induced into complete remission have a projected survival comparable to age-matched controls. While purine nucleoside analogues induce profound T-cell dysfunction and longstanding immunosuppression, the incidence of secondary malignancies is apparently not increased. Infections still pose a threat to these patients, and effective strategies for treating this disease that do not further compromise the immune system are needed. Patients with this disease should be encouraged to participate in ongoing clinical trials to better define the optimal treatment regimen. New studies should explore the combination of pentostatin and rituxan in treating the typical form of hairy-cell leukemia, and the incorporation of new agents for those with the rare variant form of this disease.