Metacognition in psychophysical judgment: an unfolding view of comparative judgments of mental workload.

An experiment is reported in which it was found that when subjects were required to indicate which of two visual extents was more difficult to categorize as "long" or "short," they executed these categorizations and then measured the distance of the representation of each stimulus from the long-short category boundary; the stimulus nearer the boundary was judged to be the more difficult. When they were requested to indicate which was easier to categorize, they selected the alternative that was farther. Coombs's theory of data (1952, 1964) and his unfolding theory of preferential choice (1950, 1964) provided the conceptualization of metacognition in this psychophysical task context. Strong support for the probabilistic version of unfolding theory was obtained from the observed selective effects of laterality on the levels of stochastic transitivity attained for various classes of triples and the reliably longer times for comparisons with bilateral pairs than with unilateral pairs. The semantic congruity effects obtained, together with the changes in the form of the relationship between probability and response time as a function of practice, can be best accounted for by an evidence accrual theory in which the distances from the active reference point are measured and compared with a criterion on each evidence accrual. No support is provided for the view that propositionally based semantic "ease"-"difficulty" codes serve as the basis for these metacognitive comparative judgments of ease and difficulty.     

The role of central and peripheral vision in perceiving the direction of self-motion.

Three experiments were performed to examine the role that central and peripheral vision play in the perception of the direction of translational self-motion, or heading, from optical flow. When the focus of radial outflow was in central vision, heading accuracy was slightly higher with central circular displays (10 degrees-25 degrees diameter) than with peripheral annular displays (40 degrees diameter), indicating that central vision is somewhat more sensitive to this information. Performance dropped rapidly as the eccentricity of the focus of outflow increased, indicating that the periphery does not accurately extract radial flow patterns. Together with recent research on vection and postural adjustments, these results contradict the peripheral dominance hypothesis that peripheral vision is specialized for perception of self-motion. We propose a functional sensitivity hypothesis--that self-motion is perceived on the basis of optical information rather than the retinal locus of stimulation, but that central and peripheral vision are differentially sensitive to the information characteristic of each retinal region.     

Extracting thresholds from noisy psychophysical data.

Psychophysical studies with infants or with patients often are unable to use pilot data, training, or large numbers of trials. To evaluate threshold estimates under these conditions, computer simulations of experiments with small numbers of trials were performed by using psychometric functions based on a model of two types of noise: stimulus-related noise (affecting slope) and extraneous noise (affecting upper asymptote). Threshold estimates were biased and imprecise when extraneous noise was high, as were the estimates of extraneous noise. Strategies were developed for rejecting data sets as too noisy for unbiased and precise threshold estimation; these strategies were most successful when extraneous noise was low for most of the data sets. An analysis of 1,026 data sets from visual function tests of infants and toddlers showed that extraneous noise is often considerable, that experimental paradigms can be developed that minimize extraneous noise, and that data analysis that does not consider the effects of extraneous noise may underestimate test-retest reliability and overestimate interocular differences.     

The word-superiority effect does not require a T-scope.

Six experiments examined the possibility of obtaining a word-superiority effect (WSE) without the use of brief stimulus exposures or a poststimulus mask. In each experiment, subjects were presented a stimulus string and two alternative strings that differed by a single letter (Reicher, 1969). The alternatives and stimulus remained in view until subjects responded, and subjects were under no pressure to respond quickly. In Experiments 1-3, the stimuli were presented in very small type so that they were difficult to see. Subjects were significantly more accurate with words than with nonwords, letters embedded among digits, or letters embedded among number signs (#s). In Experiments 4 and 5, the stimuli were embedded in a simultaneously present pattern mask. Subjects were significantly more accurate with words than with single letters by themselves. In the final experiment, the stimuli were presented in a mask with specific spatial frequency characteristics, and performance was significantly better with words than with nonwords. The WSE is a more general phenomenon than previously supposed; it is not limited to a tachistoscopic exposure.     

Haptic probing: perceiving the length of a probe and the distance of a surface probed.

Knowing about the properties of objects by wielding them and knowing about the distances of surfaces by striking them with objects as probes are examples of dynamic or effortful touch. Six experiments focused on the invariant mechanical parameters that couple the time-varying states (displacements, velocities) of hand-held rods to the time-varying torques and forces imposed upon them by wielding and probing. There were three major conclusions. First, when a probe is wielded without contact, perceived probe length is a function of the probe's rotational inertia; however, with contact, perceived probe length is affected by the rotational inertia and the distance of the point of contact from the probe's center of percussion. Second, when a surface is struck with a probe, perceived surface distance is affected by the probe's rotational inertia and the angle of inclination of the probe at contact. Third, under seemingly identical conditions of probing, either probe length or surface distance can be perceived selectively without confusion. Results were discussed in terms of haptic information, haptic attention, and the dynamics of probing.     

A novel contact-lens system to assess visual hemispheric asymmetries.

A soft contact-lens system for achieving unilateral visual stimulation in a free vision format is described. Initial testing with light transmittance and visual perimetry indicated that the lenses created artificial visual-field deficits. The efficacy of the lenses as a technique for lateralizing visual input was evaluated by examining within-subject differences in performance on two visuospatial tasks. Speed and accuracy of performance were greater with visual input directed to the right hemisphere. These data support the lens design as a useful alternative to tachistoscopic procedures and previous lens systems.     

Using subtests of the Brain Age Quotient to screen for cognitive deficits among substance abusers.

The subtests of the Brain Age Quotient, a brief neuropsychological battery, were used to screen for cognitive impairment in a sample of 112 substance abusers. Each of the subtests was scored, using newly developed T scores corrected for age, education, and gender, for which a mean battery score of T less than 40 indicates general cognitive impairment. The chance-corrected agreement in finding cognitive dysfunction between this battery and the Average Impairment Rating T score from the Halstead-Reitan battery was adequate, kappa = .81. This result suggests that, for discerning global cognitive impairment, this relatively brief neurodiagnostic screening device may be an attractive alternative to the more time-consuming Halstead-Reitan battery.     

Effects of color of paper on which the Profile of Mood States is printed on the psychological states it measures.

The Profile of Mood States was printed on four different colors of paper (yellow, red, green, blue) and white to test whether the color of paper would influence mood state scores of 246 college students. Univariate analyses of variance identified color effects only on the Fatigue scale.     

Imputation of missing categorical data by maximizing internal consistency

This paper suggests a method to supplant missing categorical data by reasonable replacements. These replacements will maximize the consistency of the completed data as measured by Guttman's squared correlation ratio. The text outlines a solution of the optimization problem, describes relationships with the relevant psychometric theory, and studies some properties of the method in detail. The main result is that the average correlation should be at least 0.50 before the method becomes practical. At that point, the technique gives reasonable results up to 10–15% missing data.We thank Anneke Bloemhoff of NIPG-TNO for compiling and making the Dutch Life Style Survey data available to use, and Chantal Houée and Thérèse Bardaine, IUT, Vannes, France, exchange students under the COMETT program of the EC, for computational assistance. We also thank Donald Rubin, the Editors and several anonymous reviewers for constructive suggestions.