The effect of category learning on sensitivity to within-category correlations

A salient property of many categories is that they are not just sets of independent features but consist of clusters of correlated features. Although there is much evidence that people are sensitive to between-categories correlations, the evidence about within-category correlations is mixed. Two experiments tested whether the disparities might be due to different learning and test tasks. Subjects learned about categories either by classifying items or by inferring missing features of items. Their knowledge of the correlations was measured with classification, prediction, typicality, and production tests. The inference learners, but not the classification learners, showed sensitivity to the correlations, although different tests were differentially sensitive. These results reconcile some earlier disparities and provide a more complete understanding of people's sensitivities to within-category correlations.     

MMPI-A scores and high points of male juvenile delinquents: scales 4, 5, and 6 as markers of juvenile delinquency

The Minnesota Multiphasic Personality Inventory-Adolescent (MMPI-A) clinical, supplementary, and content scale score patterns for 655 male delinquents were examined. Low scores on Scale 5 (Masculinity/Femininity) were found to be the most frequent deviation, followed by elevations on Scales 6 (Paranoia) and 4 (Psychopathic Deviate). This is consistent with previous research, although the importance of Scale 5 deviations has been little noted because of the traditional focus on scale elevations only. Classification analysis indicated that a combination of MMPI-A scales discriminated between this delinquent sample and the normative sample, with a sensitivity of 90%-95% and a specificity of 80%-85%. This level of sensitivity was maintained in a replication sample (N = 473).     

Consolidation theory and retrograde amnesia in humans

Recent research on the cognitive dysfunctions experienced by human anmesic patients indicates that very long term (multidecade) changes may occur in memory.Flat retrograde amnesia (RA), consisting of a uniform memory deficit for information from all preamnesia time periods, indicates a simple, monolithic retrieval problem, whereasgraded RA, with greater memory deficits for information from recent as opposed to remote time periods, suggests the presence of a gradual long-term encoding, or consolidation, process. An evaluation of 247 outcomes from 61 articles provides strong evidence of graded RA across different cerebral injuries, materials, and test procedures, as well as in measures of both absolute and relative (patient vs. control) performance. Future conceptualizations of human memory should address the possibility that memories increase in resistance to forgetting, or reduction in trace fragility, across many decades.     

Overt and covert object-based attention

To examine the role of perceptual object representations in the control of eye movements and attention, a pair of experiments adapted the object-cuing paradigm of Egly, Driver, and Rafal (1994) to require eye movements. Displays were pairs of adjacent rectangles, each containing two characters. Observers were asked to make a speeded judgment of a target character’s orientation, and a cue was provided prior to target/distractor onset to indicate the target’s likely location. Gaze-contingent presentation of target and distractors was used to demand overt scanning of displays. Eye movements during task performance evinced two forms of object-based effects. First, saccades following fixation on an invalidly cued item were more likely to be made within the cued rectangle than between rectangles. Second, saccades within the cued rectangle were preceded by shorter dwell times than saccades between rectangles. Extrafoveal processing of stimuli within the cued rectangle, however, was not facilitated, suggesting that covert attention was not allocated more densely within the cued than within the uncued object.     

Dissociating familiarity from recollection in human recognition memory: Different rates of forgetting over short retention intervals

Two functionally distinct forms of recognition memory have been identified in human and nonhuman species—the ability to recollect qualitative information about previous events, and the ability to differentiate between familiar and novel stimuli. Separate dual-process theories have been developed in the animal and human literatures to account for these findings. However, it is not clear whether these theories describe the same two underlying memory processes. On the basis of animal studies of medial temporal lobe function, familiarity is expected to exhibit disproportionately fast forgetting compared with recollection over short retention intervals. We tested this prediction in healthy human subjects by examining recognition forgetting rates across a range of 8–32 intervening items and found significant forgetting in the accuracy of familiarity-based discriminations and no evidence of forgetting in the accuracy of recollection-based discriminations. In agreement with the results from nonhuman species, the present results indicate that item familiarity decreases more rapidly than recollection over short retention intervals.     

Extending the ALCOVE model of category learning to featural stimulus domains

The ALCOVE model of category learning, despite its considerable success in accounting for human performance across a wide range of empirical tasks, is limited by its reliance on spatial stimulus representations. Some stimulus domains are better suited to featural representation, characterizing stimuli in terms of the presence or absence of discrete features, rather than as points in a multidimensional space. We report on empirical data measuring human categorization performance across a featural stimulus domain and show that ALCOVE is unable to capture fundamental qualitative aspects of this performance. In response, a featural version of the ALCOVE model is developed, replacing the spatial stimulus representations that are usually generated by multidimensional scaling with featural representations generated by additive clustering. We demonstrate that this featural version of ALCOVE is able to capture human performance where the spatial model failed, explaining the difference in terms of the contrasting representational assumptions made by the two approaches. Finally, we discuss ways in which the ALCOVE categorization model might be extended further to use “hybrid” representational structures combining spatial and featural components.     

Temporal tuning in the acquisition of cognitive skill

Thetemporal tuning hypothesis suggests that individuals adjust the timing of cognitive performances to achieve temporal coordination of mental processes and the data on which they operate, and that this adjustment becomes more precise with practice. Participants in two experiments performed self-paced multiple-step arithmetic tasks in which the information needed for each step was briefly displayed at the participants’ request. Timing constraints were manipulated by varying between subjects the delay between requests and displays of information. In Experiment 1, both operators and operands appeared step by step, and participants achieved a modest degree of temporal adjustment that did not change with practice. In Experiment 2, participants could preview operators while operands appeared step by step. In that experiment, participants achieved more precise temporal adjustment, and the amount of adjustment increased with practice. These results demonstrate the phenomenon of temporal tuning in symbolic cognitive skills and suggest some constraints on the ability to anticipate the time course of one’s mental processes.     

Conflicts of interest in science in Armenia

The author describes problems facing Armenia in reorganization of the structure of science in the post-socialist era with the aim of utilizing limited state resources more efficiently by reducing the number of separate scientific institutes, concentrating on essential core subjects required by the nation and encouraging all other projects to compete in the international arena for grant sponsorship. An earlier version of this paper was presented at an International Conference on “Conflict of Interest and its Significance in Science and Medicine” held in Warsaw, Poland on 5–6 April, 2002.