Detectability as a function of target location: effects of spatial configuration

Marked differences in detectability as a function of spatial location, a "detectability gradient," are observed when subjects are required to detect a briefly exposed target pattern of uncertain location in the presence of a number of nontarget patterns. Target detectability also is inversely related to the number of nontarget patterns which are present in this search paradigm. These previous findings provide strong evidence for a serial process in which increasing probability of error occurs during a scan of a rapidly degrading neural representation of the visual image following a brief exposure to the stimuli. It is not yet established whether this scan is attentional or perceptual in nature. The present experiments test the hypothesis of an attentional scan by presenting the target and nontarget patterns in spatially segregated groups. If the scan is attentional, then target detectability under these circumstances would be expected to exhibit the characteristic phenomenon of "group processing"--a close clustering of detection performance for targets located within a group and large differences in detectability across groups. As no evidence for group processing was observed, the results fail to support the view that the scan is attentional in nature but are fully consistent with a nonattentional scan.     

Performance objectives in the stance phase of human pathological walking

Permanent disruption of aspects of a highly learned skill such as walking force adaptations to occur to the movement. Firstly the body must determine what factors will guide the formation of the new walking pattern, and secondly that new movement pattern must be learned. Frequently the questionable assumption is made that the performance objectives of the new skill are the same as the original. This work used non-linear optimal control and multiple segment simulation to evaluate the ability of several possible objective functions to predict pathological walking patterns. These predictions were then also compared to the results from normal walking. Preliminary results indicate the performance objectives of pathological gaits may be quite different from those of normals. Some support was also provided for the existence of simultaneous multiple performance objectives in complex movements.     

Serial processing of visual spatial patterns in a search paradigm

Previous experiments in this laboratory employing a search paradigm have found highly significant differences in the detectability of a briefly exposed target pattern as a function of the spatial location of the target when it is presented simultaneously with a number of discriminably different nontarget patterns. These detectability differences, at loci equidistant from the fovea, could not be accounted for by any known variation in retinal spatial resolution or by differential lateral masking effects of the target by nearby nontarget patterns. These observations led to the hypothesis that the target in these experiments was detected by a serial mechanism which "scanned" a persisting but rapidly degrading neural representation of the visual scene with increasing detection failures the later in time the scan processed the location occupied by the target. If this hypothesis is correct, then target detectability should vary inversely with the number of stimuli which must be examined. The present experiment confirmed this expectation. A mathematical model of such a serial scanning process also predicts other, less obvious, effects on target detectability which were observed when the number of nontarget patterns was changed.     

Risk perceptions and participation in colorectal cancer screening

Compared individuals at high versus average risk for colorectal cancer (CRC) with respect to factors they cited as affecting their risk of developing CRC. We also examined the relationship of these risk-factor perceptions to perceived susceptibility and participation in a CRC screening test. All individuals in the high-risk group were informed that, as a sibling of someone with CRC, they were more likely to get this cancer themselves. We found minimal differences among siblings with respect to perceived susceptibility. Further, although high-risk siblings were more likely to participate in screening, only 20.2% cited heredity as a risk-increasing factor, and, among these siblings, there was no relationship between screening participation and the citation of any specific risk factors, including heredity. These findings demonstrate the need for more research examining how high-risk individuals process risk-relevant information and the effect of this information on health behavior.     

A further validation of the bem sex role inventory: A multitrait-multimethod study

The present study used a multitrait-multimethod technique [D.T. Campbell and D. W. Fiske (1959) “Convergent and Discriminant Validation by the Multitrait-Multimethod Matrix,” Psychological Bulletin, 56, 81–105] to examine Bem's [(1974) “The Measurement of Psychological Androgyny,” Journal of Consulting and Clinical Psychology, 42, 152–162] use of an instrumental-expressive dichotomy to conceptualize the Masculinity and Femininity scales of the Bem Sex Role Inventory as statistically orthogonal constructs. Results indicate that while perhaps reliable, masculinity and femininity lack clear convergent and discriminant validity. Therefore, Bem's contention that masculinity and femininity are orthogonal constructs is questioned. Results are discussed in light of trait- vs. method-driven research.     

Do different metamemory judgments tap the same underlying aspects of memory?

We compared the predictions from several kinds of metamemory judgments (on the same set of items), both in terms of their predictive accuracy and in terms of the commonality of predictions. Undergraduates made judgments about the ease with which they could learn each item in a list (ease-of-learning judgments); then they learned every item, either to a minimal criterion of learning or with overlearning, and made judgments about how well they knew each item (judgments of knowing); finally, they returned 4 weeks later for a retention session and made feeling-of-knowing judgments on every time they could not recall, after which a recognition test assessed predictive accuracy. Ease-of-learning judgments had the least predictive accuracy. Surprisingly, however, the recognition of nonrecalled items was predicted equally well by judgments of knowing (made 4 weeks earlier) as by feeling-of-knowing judgments (made immediately prior to recognition). Moreover, those two kinds of judgments were only weakly correlated with each other, which implies that they do not tap memory in the same way.     

Visual perception and the guidance of locomotion without vision to previously seen targets

Two experiments were performed to assess the accuracy and precision with which adults perceive absolute egocentric distances to visible targets and coordinate their actions with them when walking without vision. In experiment 1 subjects stood in a large open field and attempted to judge the midpoint of self-to-target distances of between 4 and 24 m. In experiment 2 both highly practiced and unpracticed subjects stood in the same open field, viewed the same targets, and attempted to walk to them without vision or other environmental feedback under three conditions designed to assess the effects on accuracy of time-based memory decay and of walking at an unusually rapid pace. In experiment 1 the visual judgments were quite accurate and showed no systematic constant error. The small variable errors were linearly related to target distance. In experiment 2 the briskly paced walks were accurate, showing no systematic constant error, and the small, variable errors were a linear function of target distance and averaged about 8% of the target distance. Unlike Thomson's (1983) findings, there was not an abrupt increase in variable error at around 9 m, and no significant time-based effects were observed. The results demonstrate the accuracy of people's visual perception of absolute egocentric distances out to 24 m under open field conditions. The accuracy of people's walking without vision to previously seen targets shows that efferent and proprioceptive information about locomotion is closely calibrated to visually perceived distance. Sensitivity to the correlation of optical flow with efferent/proprioceptive information while walking with vision may provide the basis for this calibration when walking without vision.     

Regression analyses of repeated measures data in cognitive research

Repeated measures designs involving nonorthogonal variables are being used with increasing frequency in cognitive psychology. Researchers usually analyze the data from such designs inappropriately, probably because the designs are not discussed in standard textbooks on regression. Two commonly used approaches to analyzing repeated measures designs are considered in this article. It is argued that both approaches use inappropriate error terms for testing the effects of independent variables. A more appropriate analysis is presented, and two alternative computational procedures for the analysis are illustrated.     

Properties of memory for unattended spoken syllables

Whereas previous studies on memory for unattended speech have inadvertently included acoustic interference, the present study examines memory for unattended syllables during a silent period of 1, 5, or 10 s. The primary task was to read silently (Experiments 1-3) or whisper the reading (Experiment 4). Occasionally, when a light cue occurred, the subject was to recall the most recent spoken syllable, as well as the recent reading material. Memory for both the vowels and consonants of the syllables decreased across 10 s, confirming that auditory memory does decay in the absence of acoustic interference. However, the specific patterns of memory decay for vowels versus consonants depended on task demands, including the allocation of attention and the opportunity for subvocal coding. We suggest an account of performance that includes auditory sensory and phonetic memory codes with different properties, used in combination.     

Overt responding in computer-based training

This experiment compared the extent to which students learned facts included in computer-based-training frames that required an overt response to those that did not. Frames included two types of facts: Some facts had one word missing which had to be supplied by the student (active facts). Other facts had no missing words and required no overt response (passive facts). Each student completed four 14-fact modules in random order. Two of the modules contained frames with all active facts. Each frame in the other two modules contained one active and six passive facts. Paper pretests and posttests showed that students learned twice as many facts when all facts in the module were active than when only one in seven were active. The modules that included passive facts required one-fifth the time to complete than those with only active facts. Students learned more facts per minute of training in one of the two modules that included passive facts than in the two modules with only active facts.