Post-training flexibility in category learning.

Exemplar models of categorization, which assume that people make classification decisions based on item information stored in memory, typically assume that all of the exemplars are available and inform decision-making. However, in this study, we hypothesized that people may selectively emphasize subsets of exemplars, giving rise to individual differences in categorization. To verify this hypothesis, we adopted the partial-XOR category structure in Conaway and Kurtz (Psychonomic Bulletin & Review, 24, 1312-1323 2017), which has been evident to be able to induce two major response patterns in the transfer phase: the Proximity and XOR patterns. "Experiment 1" confirmed that these two patterns could be generated if participants were trained with only the exemplars of one category or the other. In "Experiment 2", participants were asked to not only learn the category labels of all exemplars but also memorize the exemplars of only Category A (Condition A), only Category B (Condition B), or two categories (Condition AB) for a recognition test after the training phase of the categorization task. As expected, in the transfer phase, the participants tended to perform the XOR and Proximity patterns, when the exemplars of Category A and Category B were respectively targeted for the recognition test. The parameters of the SDGCM estimated by Bayesian inference for modeling the data of "Experiment 2" showed that the exemplar accessibility of Category A was larger than that of Category B for performing the XOR pattern and vice versa for performing the proximity pattern, hence verifying our hypothesis.

Category learning in rodents using touchscreen-based tasks.

Categorization is a fundamental cognitive function that organizes our experiences into meaningful "chunks." This category knowledge can then be generalized to novel stimuli and situations. Multiple clinical populations, including people with Parkinson's disease, amnesia, autism, ADHD and schizophrenia, have impairments in the acquisition and use of categories. Although rodent research is well suited for examining the neural mechanisms underlying cognitive functions, many rodent cognitive tasks have limited translational value. To bridge this gap, we use touchscreens to permit greater flexibility in stimulus presentation and task design, track key dependent measures, and minimize experimenter involvement. Touchscreens offer a valuable tool for creating rodent cognitive tasks that are directly comparable to tasks used with humans. Touchscreen tasks are also readily used with cutting-edge neuroscientific methods that are difficult to do in humans such as optogenetics, chemogenetics, neurophysiology and calcium imaging (using miniscopes). In this review, we show advantages of touchscreen-based tasks for studying category learning in rats. We also address multiple factors for consideration when designing category learning tasks, including the limitations of the rodent visual system, experimental design, and analysis strategies.