Temporal integration and segregation of brief visual stimuli: Patterns of correlation in time

Two brief sequential displays separated by a brief interstimulus interval (ISI) are often perceived as a temporally integrated unitary configuration. The probability of temporal integration can be decreased by increasing the ISI or (counterintuitively) by increasing stimulus duration. We tested three hypotheses of the relative contributions of stimulus duration and ISI to the breakdown of temporal integration (the storage, processing, and temporal correlation hypotheses). In the first of two experiments, stimulus duration and ISI were varied factorially, and estimates of temporal integration were obtained with a form-part integration task. The second experiment was a replication of the first at two levels of stimulus intensity. The outcomes were inconsistent with the storage and processing options, but confirmed predictions from the temporal correlation hypothesis. Whether two sequential stimuli are perceived as temporally integrated or disjoint depends not on the availability of visible persistence, but on the emergence of a neural code that is based on the temporal correlation between the two visual responses.     

Numerical comparison processes

The relative lengths of two rows of objects systematically affected the time to make judgments of the relative number of objects. The time to decide which row contained more objects generally increased with the amount of incongruity between length and number (e.g., reaction time was long when the numerically larger row was the shorter of the two). In addition, the time to decide that the rows contained an equal number of objects increased with the disparity in length between the rows. These results suggest that length information was used in the numerical comparison process. A model that uses an internal transformation of row length is proposed to account for the results.     

Seeing big things: overestimation of heights is greater for real objects than for objects in pictures

In six experiments we demonstrate that the vertical-horizontal illusion that is evoked when viewing photographs and line drawings is relatively small, whereas the magnitude of this illusion when large objects are viewed is at least twice as great. Furthermore, we show that the illusion is due more to vertical overestimation than horizontal underestimation. The lack of a difference in vertical overestimation between pictures and line drawings suggests that vertical overestimation in pictures depends solely on the perceived physical size of the projection on the picture surface, rather than on what is apparent about an object's represented size. The vertical-horizontal illusion is influenced by perceived physical size. It is greater when viewing large objects than small pictures of these same objects, even when visual angles are equated.     

Performance variability is related to change in cognition: evidence from the Victoria Longitudinal Study

Performance variability across repeated task administrations may be an important indicator of age-related cognitive functioning. In the present investigation, the authors examined whether age differences and change in inconsistency were related to 6-year (3 occasion) cognitive change. Inconsistency scores were computed from 4 reaction time tasks performed by 446 older adults (54-89 years). Replicating previous cross-sectional results, greater inconsistency was observed for older participants even after controlling for differences in response speed. New longitudinal results demonstrated (a) associations between inconsistency at baseline measurement and 6-year change in cognitive performance; (b) longitudinal change in inconsistency; and (c) intraindividual covariation between 6-year change in inconsistency and 6-year change in level of cognitive function. These findings support the view that performance variability serves as a marker of cognitive aging.     

Relationships between metamemory, memory predictions, and memory task performance in adults

A cross-sectional sample of adults recalled categorized word lists and narrative texts. Subjects gave performance predictions before each of 3 recall trials for each task. Older subjects had poorer memory performance and also predicted lower performance levels than did younger subjects. The LISREL models suggested (a) direct effects of memory self-efficacy (MSE) on initial predictions; (b) upgrading of prediction-performance correlations across trials, determined by direct effects of performance on subsequent predictions; (c) significant effects of a higher order verbal memory factor on MSE; and (d) an independent relationship of text recall ability to initial text recall performance predictions. These results lend support to the theoretical treatment of predictions as task-specific MSE judgments.     

Optimal choice of rater teams II: Applications

In a previous paper [Elashoff 1969], we derived optimal rater teams for a particular formulation of the dichotomous rater problem. Here, we describe a computer-based procedure for selecting good rater teams in practice; we apply the procedure to the selection of items for a psychological inventory. This research was supported in part by the author's predoctoral fellowship from the National Institutes of Health and by National Science Foundation Grant GS-341, and National Institutes of Health Grants FR-3 and FR-122.     

Contribution of visual and semantic proximity to identification performance in a viral encephalitis patient

Identification deficits were investigated in F.S., a patient with herpes simplex viral encephalitis. F.S.'s confrontation naming abilities were assessed for multiple repetitions of 12 line drawings of artifacts. Six of the line drawings consisted of psychologically "close" objects (i.e., objects that share many visual and semantic features with other objects) and 6 were psychologically "disparate" objects (i.e., objects that share few, if any, visual and semantic features with other objects). F.S. correctly named all of the objects from the "disparate" category but only 47% of the objects from the "close" category. We also tested F.S. using novel, computer-generated shapes that were paired with artifact labels. We paired semantically close or disparate labels to shapes and F.S. attempted to learn these pairings. Overall, F.S.'s shape-label confusions were most detrimentally affected when we used labels that referred to objects that were visually close and semantically distinct. Results indicate that, at least for our patient, visual similarity contributed the most to his identification errors.     

Dynamic illusion effects in a reaching task: evidence for separate visual representations in the planning and control of reaching.

The effects of an orientation illusion on perception and 2 different actions were investigated. An 8-cm x 2-cm cylindrical bar was placed in front of participants at various orientations. A background grating was used to induce an orientation illusion. In a perception task, the illusion affected participants' ability to align the bar with their sagittal planes. In one reaching task, a similar effect of the illusion was found on the choice between 2 possible grasping postures. In a second reaching task involving a single grasping posture, the orientation illusion affected the orientation of the hand at the beginning of the reach but not near its end. The authors argue that reaching trajectories are planned and initiated through a context-dependent representation but are corrected on-line through a context-independent representation. The relation of this model to a more general dichotomy between perception and action is discussed.     

Mild memory deficits differentially affect 6-year changes in compensatory strategy use

The authors examined memory compensation techniques used by older adults from 2 memory status groups, not impaired control (NIC) and mild memory deficit (MMD), both at baseline and across a 6-year (3-wave) interval. The groups were derived from a parent sample of 55- to 85-year-old adults from the Victoria Longitudinal Study (NIC baseline, n = 276; memory > parent sample mean; MMD baseline, n = 79; memory > 1 standard deviation below parent sample mean). Multilevel modeling was used to test 3 research questions concerning differences in initial use of, and 6-year changes and variability in, memory compensation. Initial group differences were observed for both a memory compensation technique and a general compensation indicator. Significant differences in 6-year change patterns were observed for 2 memory compensation techniques (recruitment of human memory assistance, investment of extra effort in memory tasks). Interactions of group status and wave showed that older adults with MMD declined in their use of memory compensation strategies, whereas initially NIC older adults increased their use of compensatory techniques over the 6 years.