Biomedical subjects

Emmanuel M Pothos

Publications and source records attributed to Emmanuel M Pothos.

6 recordsLinked to original sources

PubMed2005

The rules versus similarity distinction.

The distinction between rules and similarity is central to our understanding of much of cognitive psychology. Two aspects of existing research have motivated the present work. First, in different cognitive psychology areas we typically see different conceptions of rules and similarity; for example, rules in language appear to be of a different kind compared to rules in categorization. Second, rules processes are typically modeled as separate from similarity ones; for example, in a learning experiment, rules and similarity influences would be described on the basis of separate models. In the present article, I assume that the rules versus similarity distinction can be understood in the same way in learning, reasoning, categorization, and language, and that a unified model for rules and similarity is appropriate. A rules process is considered to be a similarity one where only a single or a small subset of an object's properties are involved. Hence, rules and overall similarity operations are extremes in a single continuum of similarity operations. It is argued that this viewpoint allows adequate coverage of theory and empirical findings in learning, reasoning, categorization, and language, and also a reassessment of the objectives in research on rules versus similarity.

Animals↗

PubMed2005

Unsupervised categorization and category learning.

When people categorize a set of items in a certain way they often change their perceptions for these items so that they become more compatible with the learned categorization. In two experiments we examined whether such changes are extensive enough to change the unsupervised categorization for the items-that is, the categorization of the items that is considered more intuitive or natural without any learning. In Experiment 1 we directly employed an unsupervised categorization task; in Experiment 2 we collected similarity ratings for the items and inferred unsupervised categorizations using Pothos and Chater's (2002) model of unsupervised categorization. The unsupervised categorization for the items changed to resemble more the learned one when this was specified by the suppression of a stimulus dimension (both experiments), but less so when it was almost specified by the suppression of a stimulus dimension (Experiment 1, nonsignificant trend in Experiment 2). By contrast, no changes in the unsupervised categorization were observed when participants were taught a classification that was specified by a more fine tuning of the relative salience of the two dimensions.

Association Learning↗

PubMed2005

Expectations about stimulus structure in implicit learning.

In two experiments, artificial grammar learning was used to create learning tasks of identical symbolic complexity that differed in terms of the instructions and the appearance of the stimuli. In Experiment 1, the stimuli were letter strings that appeared in either upper- or lowercase; however, letter case was irrelevant to the learning task. Participants were unable to take into account the instruction to ignore letter case. In Experiment 2, the stimuli were sequences of cities that corresponded to the routes of a traveling salesman. It was assumed that participants would adopt the expectation that the salesman would prefer short journeys. When the structure of the stimuli was inconsistent with this expectation, performance on the learning task was inhibited. The results suggest that there are circumstances in which explicit expectations about the structure of a set of stimuli can affect implicit learning of the stimuli.

Humans↗

PubMed2004

Investigating learning deficits associated with dyslexia.

An artificial grammar learning task was used to define two learning tasks of identical complexity at the symbolic level, but which differed in terms of stimulus format. The stimuli in one learning task were created so as to encourage participants to perceive each stimulus as a whole, with less emphasis on the stimulus constituent elements (the 'embedded' stimuli), while in the second task the constituent elements of each stimulus were emphasized by presenting them serially (the 'sequences' stimuli). Using a between participants design, dyslexic participants performed equally well in the two versions of the learning task. By contrast, non-dyslexic participants performed as well as dyslexic ones with the embedded stimuli but were impaired in the sequences stimuli. This finding was interpreted as showing that dyslexic participants were less able, compared to controls, to process individual stimulus elements of both the sequences and the embedded stimuli, consistently with recent work associating dyslexia with problems in attention focusing and shifting.

Adolescent↗

PubMed2004

Information about the logical structure of a category affects generalization.

This paper considers whether information about the logical structure of a category affects how people generalize. We carried out three experiments with the following structure: participants were first presented with a set of training items, and were subsequently asked to decide whether new items belonged to the same category as the training items. Each experiment had two conditions that differed only in terms of the category label provided for the training items; different category labels conveyed different information about the logical structure of the category to which the training items were supposed to belong. In all cases, participants' generalization was greatly affected by such information. Our results suggest that people make the default assumption that category labels correspond to groupings of highly similar objects.

Adult↗

PubMed2002

Cognitive bias for alcohol-related information in inferential processes.

Cognitive biases for alcohol-related stimuli have been shown to play a major role in the maintenance of alcohol addiction, thus making their study an issue of paramount importance. Such cognitive biases have been traditionally investigated with low-level, non-inferential processes, such as the Stroop task [for a review see Psychol. Bull. 120 (1996) 3]. However, explanations for these effects [for example, the current-concerns explanation; Motivation, Attention, and Volition (1987) 336] posit that biases should mediate cognitive processes more generally, not limited to a single aspect of cognition. In the present study, we addressed this issue within an experimental paradigm extensively used for the study of learning and inference. Participants who were heavy users of alcohol were impaired in the task when the stimuli were alcohol-related but not impaired when the stimuli were neutral. By contrast, participants who were light users of alcohol performed equivalently on the alcohol-related and neutral versions of the learning task.

Adolescent↗