Accuracy, Scope, and Flexibility of Models

Traditionally, models are compared on the basis of their accuracy, their scope, and their simplicity. Simplicity is often represented by parameter counts; the fewer the parameters, the simpler the model. Arguments are presented here suggesting that simplicity has little place in discussions of modeling; instead, the concept of flexibility should be substituted. When comparing two models one should be wary of the possibility of their differential flexibility. Several methods for assessing relative flexibility are possible, as represented in this special issue of the Journal of Mathematical Psychology. Here, the method of cross-validation is applied in the comparison of two models, a linear integration model (LIM) and the fuzzy-logical model of perception (FLMP), in the fitting of 44 data sets concerning the perception of layout seen among three panels with the presence or absence of four sources of information for depth. Prior to cross-validation the two models performed about equally well; after cross-validation LIM was statistically superior to FLMP, but the overall pattern of fits remained nearly the same for both models. Copyright 2000 Academic Press.     

Schizophrenia outpatients' perceptions of their parents: is expressed emotion a factor?

The factors that mediate the association between expressed emotion (EE) and relapse in schizophrenia patients are still unknown. Many researchers hypothesize that interactions with high-EE individuals are stressful for patients, leaving them vulnerable to relapse. It would be useful to investigate whether patients perceive interactions with high-EE parents as stressful. In this study, associations were examined between levels of EE in parents and the types of personal memories patients had about these parents. EE ratings were obtained for both parents of 27 schizophrenia outpatients, and patients were asked to describe "happy, nonstressful" memories and "unhappy, stressful" memories during 2 interviews. Patients recounted fewer nonstressful memories and more stressful memories about high-versus low-EE parents. Implications of these results are discussed.     

Seeking one’s heading through eye movements

A study of eye movements during simulated travel toward a grove of four stationary trees revealed that observers looked most at pairs of trees that converged or decelerated apart. Such pairs specify that one’s direction of travel, calledheading, is to the outside of the near member of the pair. Observers looked at these trees more than those that accelerated apart; such pairs do not offer trustworthy heading information. Observers also looked at gaps between trees less often when they converged or diverged apart, and heading can never be between such pairs. Heading responses were in accord with eye movements. In general, if observers responded accurately, they had looked at trees that converged or decelerated apart; if they were inaccurate, they had not. Results support the notion that observers seek out their heading through eye movements, saccading to and fixating on the most informative locations in the field of view.     

Categorical <Emphasis Type="Italic">and</Emphasis> associative relations increase false memory relative to purely associative relations

The goal of the present study was to examine the contributions of associative strength and similarity in terms of shared features to the production of false memories in the Deese/Roediger–McDermott list-learning paradigm. Whereas the activation/monitoring account suggests that false memories are driven by automatic associative activation from list items to nonpresented lures, combined with errors in source monitoring, other accounts (e.g., fuzzy trace theory, global-matching models) emphasize the importance of semantic-level similarity, and thus predict that shared features between list and lure items will increase false memory. Participants studied lists of nine items related to a nonpresented lure. Half of the lists consisted of items that were associated but did not share features with the lure, and the other half included items that were equally associated but also shared features with the lure (in many cases, these were taxonomically related items). The two types of lists were carefully matched in terms of a variety of lexical and semantic factors, and the same lures were used across list types. In two experiments, false recognition of the critical lures was greater following the study of lists that shared features with the critical lure, suggesting that similarity at a categorical or taxonomic level contributes to false memory above and beyond associative strength. We refer to this phenomenon as a “feature boost” that reflects additive effects of shared meaning and association strength and is generally consistent with accounts of false memory that have emphasized thematic or feature-level similarity among studied and nonstudied representations.     

Left-Right Differences on Timed Motor Examination in Children

Age-related change in the difference between left- and right-side speed on motor examination may be an important indicator of maturation. Cortical maturation and myelination of the corpus callosum are considered to be related to increased bilateral skill and speed on timed motor tasks. We compared left minus right foot, hand, and finger speed differences using the Revised Physical and Neurological Assessment for Subtle Signs (PANESS; Denckla, 1985 Denckla, M. B. 1985. Revised neurological examination for subtle signs. Psychopharmacology Bulletin, 21: 773–779. [PubMed], [Web of Science ®] , [Google Scholar]); examining 130 typically developing right-handed children (65 boys, 65 girls) ages 7–14. Timed tasks included right and left sets of 20 toe taps, 10 toe-heel alternation sequences, 20 hand pats, 10 hand pronate-supinate sets, 20 finger taps, and 5 sequences of each finger-to-thumb apposition. For each individual, six difference scores between left- and right-sided speeded performances of timed motor tasks were analyzed. Left-right differences decreased significantly with age on toe tapping, heel-toe alternations, hand pronation-supination, finger repetition, and finger sequencing. There were significant gender effects for heel-toe sequences (boys showing a greater left-right difference than girls), and a significant interaction between age and gender for hand pronation-supination, such that the magnitude of the left-right difference was similar for younger, compared with older girls, while the difference was significantly larger for younger, compared to older boys. Speed of performing right and left timed motor tasks equalizes with development; for some tasks, the equalization occurs earlier in girls than in boys.     

Exploring how symptoms of attention-deficit/hyperactivity disorder are related to reading and mathematics performance: general genes, general environments

Children with attention-deficit/hyperactivity disorder (ADHD) tend to perform more poorly on tests of reading and mathematical performance than their typical peers. Quantitative genetic analyses allow for a better understanding of the etiology of ADHD and reading and mathematics outcomes, by examining their common and unique genetic and environmental influences. Analyses were conducted on a sample 271 pairs of 10-year-old monozygotic and dizygotic twins drawn from the Western Reserve Reading and Mathematics Project. In general, the results suggested that the associations among ADHD symptoms, reading outcomes, and math outcomes were influenced by both general genetic and general shared-environment factors. The analyses also suggested significant independent genetic effects for ADHD symptoms. The results imply that differing etiological factors underlie the relationships among ADHD and reading and mathematics performance. It appears that both genetic and common family or school environments link ADHD with academic performance.     

Perceiving motion while moving: how pairwise nominal invariants make optical flow cohere

Computer-generated sequences simulated observer movement toward 10 randomly placed poles, 1 moving and 9 stationary. When observers judged their direction of movement, or heading, they used 3 related invariants: The (a) convergence and (b) decelerating divergence of any 2 poles specified that heading was to the outside of the nearer pole, and the (c) crossover of 2 poles specified that heading was to the outside of the farther pole. With all poles stationary, the field of 45 pairwise movements yielded a coherent specification of heading. With I pole moving with respect to the others, however, the field could yield an incoherent heading solution. Such incoherence was readily detectable; similar pole motion leading to coherent flow, however, was less readily detectable.     

Gaze-eccentricity effects on road position and steering

The effects of gaze eccentricity on the steering of an automobile were studied. Drivers performed an attention task while attempting to drive down the middle of a straight road in a simulation. Steering was biased in the direction of fixation, and deviation from the center of the road was proportional to the gaze direction until saturation at approximately 15 degrees gaze-angle from straight ahead. This effect remains when the position of the head was controlled and a reverse-steering task was used. Furthermore, the effect was not dependent on speed but reversed when the forward movement of the driver was removed from the simulation. Thus, small deviations in a driver's gaze can lead to significant impairments of the ability to drive a straight course.     

Images, imagination, and movement: pictorial representations and their development in the work of James Gibson

For more than 30 years James Gibson studied pictures and he studied motion, particularly the relationship between movement through an environment and its visual consequences. For the latter, he also struggled with how best to present his ideas to students and fellow researchers, and employed various representations and formats. This article explores the relationships between the concepts of the fidelity of pictures (an idea he first promoted and later eschewed) and evocativeness as applied to his images. Gibson ended his struggle with an image of a bird flying over a plane surrounded by a spherical representation of a vector field, an image high in evocativeness but less than completely faithful to optical flow.