What is the speed to transparent and kinetic-boundary displays?

To compare transparent motion and kinetic boundaries with unidirectional motion, in many studies the relative motion is generated by superimposing or adjoining unidirectional motions oriented in opposite directions. The presumption, tacitly underlying this comparison, is that the two oppositely directed velocities are independent of one another as far as their speed is concerned, i.e. the speed of the relative motion is presumed to be equivalent to the speed of the unidirectional components. Here we report that the relative motion between dots moving in opposite directions augments perceived speed. A constant-stimuli procedure was used to pair transparent-motion or kinetic-boundary displays with unidirectional motion, and human observers were asked to match the speed of the relative and unidirectional motions. The results show that transparency and kinetic boundaries increase the perceived visual speed by about 50%, compared with the speed of the individual components.     

Time course of word identification and semantic integration in spoken language

The minimum duration signal necessary to identify a set of spoken words was established by the gating technique; most words could be identified before their acoustic offset. Gated words were used as congruous and incongruous sentence completions, and isolation points established in the gating experiment were compared with the time course of semantic integration evident in event-related brain potentials. Differential N400 responses to contextually appropriate and inappropriate words were observed about 200 ms before the isolation point. Semantic processing was evident before the acoustic signal was sufficient to identify the words uniquely. Results indicate that semantic integration can begin to operate with only partial, incomplete information about word identity. Influences of semantic constraint, word frequency, and rate of presentation are described.     

Change of spatial field effects in 16- to 20-week-old infants

Infants from 16 to 20 weeks were presented with objects moving across a 60-cm distance. Tracking increased between 16 and 18 weeks, reaching increased at 18 weeks, and arm lifts (swipes) showed no age change. A right spatial field bias in tracking disappeared gradually. Swipes occurred most often in front of the object, when it was moving in the center field, presumably as reactions due to spatial proximity. Reaching occurred in the peripheral spatial fields in the younger infants, but in the older infants most often in the center spatial field. Moreover, reaching occurred generally more often toward the left spatial field and predicted the emergence of tracking the left spatial field. Thus, it appeared that a bias in reaching corrected a bias in tracking. Similar effects of limb movements, especially when reaching, were found in the successful treatment of visual neglect patients in neuropsychological research.     

Fitting the psychometric function

A constrained generalized maximum likelihood routine for fitting psychometric functions is proposed, which determines optimum values for the complete parameter set--that is, threshold and slope--as well as for guessing and lapsing probability. The constraints are realized by Bayesian prior distributions for each of these parameters. The fit itself results from maximizing the posterior distribution of the parameter values by a multidimensional simplex method. We present results from extensive Monte Carlo simulations by which we can approximate bias and variability of the estimated parameters of simulated psychometric functions. Furthermore, we have tested the routine with data gathered in real sessions of psychophysical experimenting.     

Strategic aspects of reaction time in world-class sprinters

Simple reaction time (RT) is defined as the time duration following the initiation of a stimulus and the resultant first observable response. For sprinters, RT to a start should be especially important, as this may determine the outcome of the race. The aim of this study was to investigate whether sprinters (from 100 to 400 m) try to anticipate the starter's shot within the false start limit (100 msec. after the shot). Subjects were male sprinters who have reached the final of a sprint event in World Championships or Olympic Games. Analysis indicated that RT to the starting shot plays a role in the eight finalists' strategy throughout an event (requiring a total of four sprints). Four characteristics of the strategic aspects of RT were found: (i) Increased mean RT from short dashes to longer sprints (from 60 m indoor, to 100 m, 200 m, and 400 m); (ii) RT values increase as a function of race length, i.e., the RT of the first sprinter in a 4 x 100-m relay is no different from that of a 400-m sprinter; conversely, RT of the first relay sprinter in a 4 x 400-m, i.e., a 1600-m race, is significantly different from RT in a 400-m race; (iii) RT decreases from the heats to the final for the eight finalists; (iv) Decreased RT is not observable in less experienced sprinters through the qualifying rounds (junior 18- or 19-yr.-old sprinters, taking part in their own World Championships). RT must be considered a skill dependent upon experience and learning and is associated with race length. The shorter the race, the more important the RT is for the final performance (both time and place), so sprinters try to decrease RT in the shorter dashes (60 m and 100 m). In the longer sprint races (4 x 400-m relay) they are content to respond to the shot. Intermediate distance races elicit intermediate values of RT. Such behavior could be explained by the importance of RT throughout the factors which influence sprint performance and by reference to allocation of concentration resources and expenditure.     

Are European and American golf players different? Reply to Engelhardt (1997)

Analysis of 1998 statistics for individual performance in the PGA European Tour yielded significant differences between some shot-making skills (drive distance, total driving, greens in regulation, and sand saves) between the top 10 and bottom 10 money winners, replicating (with partially different results) a result found for the 1995 American PGA Tour by Engelhardt.     

HIV/AIDS and health care workers: contact with patients and attitudes towards them

Data on a range of variables associated with contact with patients with HIV/AIDS and attitudes towards them were collected from 174 Scottish health care workers. Measures of attitudes and contact (overall, social and physical) were derived from the scales devised by Pleck et al. (1988). The measure of overall contact was not significantly related to attitudes, but those with predominantly social contact with patients with HIV/AIDS had more positive attitudes towards them. This relationship was moderated by occupational characteristics, concern about working with people of unknown HIV status and neuroticism. With all these variables controlled, including social contact, those who had not received in-service training relating to HIV/AIDS had more negative attitudes. The results are discussed with regard to the measurement of social contact with patients, salient beliefs, the occupational characteristics associated with attitudes, and in-service education.     

Reading action word affects the visual perception of biological motion

In the present study, we investigate whether reading an action-word can influence subsequent visual perception of biological motion. The participant's task was to perceptually judge whether a human action identifiable in the biological motion of a point-light display embedded in a high density mask was present or not in the visual sequence, which lasted for 633 ms on average. Prior to the judgement task, participants were exposed to an abstract verb or an action verb for 500 ms, which was related to the human action according to a congruent or incongruent semantic relation. Data analysis showed that correct judgements were not affected by action verbs, whereas a facilitation effect on response time (49 ms on average) was observed when a congruent action verb primed the judgement of biological movements. In relation with the existing literature, this finding suggests that the perception, the planning and the linguistic coding of motor action are subtended by common motor representations.     

Location and shape in inhibition of return

Inhibition of return (IOR) is characterized by a delay in responding to a target preceded by an irrelevant stimulus (cue) at the same location, or, in other words, by a response delay when the same location is stimulated twice. It is not clear, however, if the same phenomenon is present when there is a repetition of a simple nonspatial attribute of the stimulus. The present study examines the repetition of shape. Six experiments were conducted. In Experiments 1, 2, 3, and 6 the stimuli were geometrical shapes, whereas in Experiments 4 and 5 letters were used. In Experiment 1 all the stimuli were presented at fixation, whereas in Experiments 2 to 6 they were presented in the periphery. In Experiments 2 and 3, location and shape of the cue and the target were independently manipulated in order to test independently inhibitory effects (IOR?) attributable to location repetition and shape repetition. Results showed an inhibitory effect for location and a much smaller inhibitory effect for shape. The latter was restricted to the cued location. Experiments 4 and 5 tested the possibility that inhibition caused by shape repetition is due to repetition blindness. Experiment 6 contrasted the presence or absence of a central neutral attractor in the delay interval between presentation of the cue and the target. Taken together the results seem to favor IOR as the basis for the inhibition caused by shape repetition.