Prior knowledge enhances the category dimensionality effect

A study of the combined influence of prior knowledge and stimulus dimensionality on category learning was conducted. Subjects learned category structures with the same number of necessary dimensions but with more or fewer additional, redundant dimensions and with either knowledge-related or knowledge-unrelated features. Minimal-learning models predict that all subjects, regardless of condition, either should learn the same number of dimensions or should respond more slowly to each dimension. Despite similar learning rates and response times, subjects learned more features in the high-dimensional than in the low-dimensional condition. Furthermore, prior knowledge interacted with dimensionality, increasing what was learned, especially in the high-dimensional case. A second experiment confirmed that the participants did, in fact, learn more features during the training phase, rather than simply inferring them at test. These effects can be explained by direct associations among features (representing prior knowledge), combined with feedback between features and the category label, as was shown by simulations of the knowledge resonance, or KRES, model of category learning.     

Vision for perception and vision for action: normal and unusual development

Evidence suggests that visual processing is divided into the dorsal ('how') and ventral ('what') streams. We examined the normal development of these streams and their breakdown under neurological deficit by comparing performance of normally developing children and Williams syndrome individuals on two tasks: a visually guided action ('how') task, in which participants posted a card into an oriented slot, and a perception ('what') task, in which they matched a card to the slot's orientation. Results showed that all groups performed worse on the action task than the perception task, but the disparity was more pronounced in WS individuals and in normal 3-4-year-olds than in older children. These findings suggest that the 'how' system may be relatively slow to develop and more vulnerable to breakdown than the 'what' system.     

The effects of revisionism on remembered emotion: the valence of older,voluntary immigrants' pre‐migration autobiographical memories

Prior research on remembered emotion demonstrates effects of revisionism in memory. The positivity bias describes preferential recall for positive emotions and the fading affect bias describes greater fading of negative versus positive emotion over time. Such effects predict that older adults would remember childhood and youth more positively than later adulthood. However, economic immigrants, whose childhood and youth reflect experiences of poverty and unemployment, may not show the effects of such revisionism. This study examined the remembered emotion of immigrant and non‐immigrant older Puerto Ricans whose early years corresponded to hard times on the island. Multilevel modelling showed that both groups exhibited the effects of the positivity and fading affect biases, but immigrants remembered childhood and youth more negatively than non‐immigrants. This suggests both accurate memory for a more negative past as well the effects of additional revisionism whereby a valued and chosen present is preferentially compared to the past. Copyright © 2006 John Wiley & Sons, Ltd.     

ELOPTA: A novel microcontroller-based operant device

Operant devices have been used for many years in animal behavior research, yet such devices a regenerally highly specialized and quite expensive. Although commercial models are somewhat adaptable and resilient, they are also extremely expensive and are controlled by difficult to learn proprietary software. As an alternative to commercial devices, we have designed and produced a fully functional, programmable operant device, using a PICmicro microcontroller (Microchip Technology, Inc.). The electronic operant testing apparatus (ELOPTA) is designed to deliver food when a study animal, in this case a bird, successfully depresses the correct sequence of illuminated keys. The device logs each keypress and can detect and log whenever a test animal i spositioned at the device. Data can be easily transferred to a computer and imported into any statistical analysis software. At about 3% the cost of a commercial device, ELOPTA will advance behavioral sciences, including behavioral ecology, animal learning and cognition, and ethology.     

Generating variables with arbitrary properties

There are occasions in psychological research where it is desirable to have available sets of variables with arbitrary intercorrelations. A quite simple procedure is described for generating pairs of such variables.     

Interpolation in structure from motion.

We investigated surface interpolation in displays of structure from motion (SFM). To do so, we introduced a new method for measuring surface perception in dynamic displays--the SFM probe. An SFM probe is a dot that moves rigidly with the dots on a simulated surface, and whose distance from that surface can be adjusted with a joystick or similar control. The displays we studied were random-dot cylinders containing a vertical strip devoid of feature points (the gap). Subjects adjusted an SFM probe, presented in the gap, until the probe dot appeared to be on the surface. Variability in probe-dot placement decreased with increasing texture density on the cylinder and increased with increasing gap width. Subjects showed a consistent bias to place the probe dot outside the cylinder. This bias increased with increasing texture density for the SFM displays. (The opposite bias was found in a static two-dimensional interpolation task with an arc whose curvature matched that of the cylinder: Subjects placed the probe dot inside the arc.) This outside bias is inconsistent with several theoretical approaches to surface interpolation.     

Reading and visual memory: remembering scenes that were never seen.

In Experiment 1 (N = 16), under conditions of high memory load (60 pictures and 50 paragraphs) and a 1-week retention interval, undergraduate subjects reported their memory for photographs of scenes (cued recall and free-recall tasks). Subjects frequently reported memory for photographs that they had actually never seen, but had read about in a brief paragraph. In Experiment 2 (N = 40), the same pattern of results was obtained with immediate testing. Experiment 2 also demonstrated that the likelihood of subjects falsely attributing scene memory (based on reading) to actually having viewed a photograph was reduced when metacognitive awareness of imaging during reading was made salient. Awareness of image creation was induced by requiring subjects to rate the paragraphs with respect to imagery vividness. Although other measures of memory remained the same, subjects in the induced-imagery condition made 50% fewer confusion errors than subjects who read the paragraphs without imagery instructions. The results are discussed in the context of Johnson and Raye's (1981) reality monitoring model.     

Psychological and sexual functioning among outpatient sexual offenders against children: A Minnesota Multiphasic Personality Inventory (MMPI) cluster analytic study

Multivariate clustering procedures were used to identify homogeneous subgroups of outpatient sex offenders against children (n=110)on the basis of the Minnesota Multiphasic Personality Inventory (MMPI). Results indicated a five-subgroup solution. Two within-normal-limits and two clinically elevated profile subgroups replicated subtypes found in previous cluster analytic studies of child sex offenders. The fifth subgroup appeared similar in MMPI profile pattern and elevation to a previously identified subtype of rapists. Discriminant analyses showed that subgroups differed along dimensions of cognitive disturbance and sexual functioning. Furthermore, levels of psychopathology corresponded with levels of sexual pathology. Results are discussed with reference to previous MMPI cluster analytic studies of sex offenders and theories of sexual aggression.Portions of this paper were presented at the meeting of the Midwestern Psychological Association, 1992, Chicago, Illinois.     

An apparatus for the assessment of prepulse inhibition in the frog

A system for studying prepulse inhibition in the leopard frog is described herein. It entails a modification of an apparatus developed almost a century ago, by Yerkes, for his investigations of hearing in the frog. With the present system, a frog is restrained in a cylindrical vessel (constructed from a 35-mm film canister), and the canister is positioned in the apparatus so that the animal’s legs hang downward. A miniature solenoid is used to deliver a startle eliciting tap to the frog’s head, and the resulting leg movement is detected by an optical densitometer. In addition to providing a convenient way to restrain frogs, our system enabled us to, in part, replicate Yerkes’s basic procedures with these subjects. As did Yerkes, we found that an acoustic signal just prior to a tap on a frog’s head inhibits the leg movement that would otherwise be elicited.