Spatial-frequency uncertainty and cuing effects on psychometric functions for contrast detection

In the present study, the effects of spatial-frequency uncertainty and cuing on psychometric functions for contrast detection of sinusoidal gratings are examined. For this purpose, psychometric functions were collected from 4 subjects under fixed-frequency, randomized-frequency, and cued-frequency conditions. The experiment was conducted with a temporal two-alternative forced-choice task, and five spatial frequencies in the range of 0.5 and 8.0 c/deg and seven contrast levels for each frequency were used. The results showed that the psychometric functions for the randomized-frequency condition were shallower than those for the fixed-frequency condition, supporting the single-band model for the uncertainty effects (Hübner, 1993a, 1993b). For the cued-frequency condition, the slopes of the functions were not clearly different from those for the randomized condition. These results clearly differ from those of Hübner (1996b), which showed, in the spatial two-alternative forced-choice task, steeper psychometric functions for the randomized-frequency condition than those for the fixed- and cued-frequency conditions, supporting the multiple-band model (Hübner, 1993a, 1993b). The difference suggests that the single-band model applies to the uncertainty effects in the temporal forced-choice task, whereas the multiple-band model does so in the spatial forced-choice task.     

Impact of Teachers' Language Expression and Message Valence when Conveying Classroom-Compliance Instructions1

This study examines how the types of language expression and message valence used by teachers to convey classroom-compliance instructions affect elementary-school children's psychological reactance and their intention to follow instructions. Altogether, 178 elementary-school children (54% girls) participated in a mixed-design experiment. Participants read four self-developed cartoons, where a hypothetical teacher conveyed classroom-compliance instructions through four expressions, and responded to questions measuring psychological reactance and the intention to follow instructions based on the cartoons. The results showed that psychological reactance was relatively significant in the high-controlling language condition. In the low-controlling language condition, the approach evoked less psychological reactance and enhanced the intention to follow instructions, whereas avoidance did so in the high-controlling language condition. Our findings offer suggestions on how teachers can improve classroom management by altering their messages in accordance with the motivation characteristics of their students.     

Reaction times and anticipatory skills of karate athletes

Two experiments were conducted to investigate the reaction times (RTs) and anticipation of karate athletes. In Experiment 1, choice RTs and simple RTs were measured with two types of stimuli. One was videotaped scenes of opponent's offensive actions, which simulated the athletes' view in real situations, and the other was static filled circles, or dots. In the choice RT task, participants were required to indicate as soon as possible whether the offensive actions would be aimed at the upper or middle level of their body, or the dot was presented either at a higher or a lower position. In the simple RT task, they were required to respond as soon as possible when the offensive action started from a static display of the opponent's ready stance, or a dot appeared on the display. The results showed significant differences between the karate athletes and the novices in the choice RT task, the difference being more marked for the video stimuli than for the dot stimuli. There was no significant difference in simple RT between the two groups of participants, for either type of stimuli. In Experiment 2, the proportions of correct responses (PCRs) were measured for video stimuli which were cut off at the seventh frame from the onset of the opponent's offensive action. The athletes yielded significantly higher PCRs than the novices. Collectively the results of the two experiments demonstrate the superior anticipatory skills of karate athletes regarding the target area of an opponent's attack (Scott, Williams, & Davids, Studies in perception and action II: Posters presented at the VIIth International conference on Event Perception and Action, Erlbaum, Hillsdale, NJ, 1993, p. 217; Wiiliams & Elliot, Journal of Sport & Exercise Psychology 21 (1999) 362), together with their advantage over novices in non-specific sensory functions (e.g., vertical discrimination).     

Analysis of simple reaction time to a sinusoidal grating by means of a linear filter model of the detection process

Simple reaction time (RT) to a sinusoidal grating was analyzed in terms of a linear filter model of the detection process. First, RT contrast functions were determined over a wide range of spatial frequencies and retinal illuminances. Second, calculating the time course of the linear filter's response, theoretical visual latency contrast functions were derived for the same conditions of spatial frequency and retinal illuminance as those in the RT measurements. Comparison of the two functions showed that the contrast dependence of the RT functions was much larger than that of the visual latency functions. The discrepancy between the two functions was satisfactorily described as a power function of the slope of the filter's response at threshold level. On the basis of these results, we propose a model of the RT process. According to the model, the RT process is mediated by a cascade that consists of a level detector, which includes a linear filter followed by a threshold device, and a differentiator of the filter's response.     

Analysis of simple reaction time to sinusoidal grating by means of a linear filter model of the detection process

Attention, Perception, & Psychophysics - Simple reaction time (RT) to a sinusoidal grating was analyzed in terms of a linear filter model of the detection process. First, RT contrast functions...     

World‐Pictures and Wittgensteinian Certainty

Although certainty is a fundamental notion in epistemology, it is less studied in contemporary analytic epistemology than other important notions such as knowledge or justification. This paper focuses on Wittgensteinian certainty, according to which the very basic dimension of our epistemic practices, the elements of our world‐pictures, are objectively certain, in that we cannot legitimately doubt them. The aim of the paper is to offer the best philosophical way to clarify Wittgensteinian certainty, in a way that is consonant with Wittgenstein's fundamental insights. The paper critiques two alternative proposals for clarifying Wittgensteinian certainty that are philosophically unsatisfying: the rule view and the proposition view. Finally, it instead shows how viewing world‐pictures as pictures, in the sense of unclear conceptions, is a more philosophically fruitful approach to understanding world‐pictures.