No abstract

No abstract

In the literature two different views on the time course of activation of "recognition units"--hypothetical units that represent identity information--are proposed. The first view assumes that the recognition units accumulate activation gradually over time. The second assumes that the activation levels increase fast initially and then start to decrease. Hagenzieker and Van der Heijden (1990) have proposed a more general information-processing model, which is compatible with both views. In this model a threshold determines what type of time course will be obtained. For below-threshold-activation values a gradual accumulation of activation will be found; for above-threshold values activation levels will first increase and then, because of inhibition, decrease. This model served as a starting-point for the present paper. Elaboration of this model led to two testable hypotheses with regard to identification performance. The first prediction is that evidence for inhibition should be observed only under relatively bright luminance conditions. The second is that, given inhibition, the amount of the effect of this inhibition should increase over time. A partial-report bar-probe task was used to test the predictions. The experiment involved two luminance conditions and the information was sampled at two different moments in time. To control for possible localization artefacts a digit-naming task was also used. Evidence for inhibition was found in both luminance conditions. In accordance with the model the amount of the effect of inhibition increased over time.

No abstract

With single-item visual displays, the facilitating effects of foreknowledge of item location have been demonstrated by using latency and accuracy as the dependent variables in detection tasks and by using latency as the dependent variable in recognition tasks. Evidence of such facilitating effects obtained by using accuracy as the dependent variable in recognition tasks is scarce and rather ambiguous. One of the difficulties in demonstrating the beneficial effects of location cuing in recognition accuracy may be the fact that in these tasks a performance baseline of no cuing is used that leaves only relatively little room for improvement. Therefore, in the present experiments, we varied the performance baseline by presenting letters on one of three imaginary circles at different distances from the fixation point, and determined, for each subject, a presentation time that resulted in an overall no-cue accuracy rate of .75. In the experimental trials, three cue conditions were used: position cue (cuing 1 of 15 possible positions), ring cue (cuing 5 positions, all on one of the three circles), and no cue (cuing all 15 possible locations). In Experiment 1, the cue conditions were randomized. In Experiment 2, the cue conditions were blocked. Significant beneficial effects of foreknowledge of position were found in both experiments. Beneficial effects of ring cuing were found only in Experiment 2. In both experiments, the benefits of cuing are positively related to room for improvement. Partial correlations show that it is, indeed, room for improvement, and not the covarying factor of distance from fixation point, that determines cuing benefits. The theoretical implications of the beneficial effects of ring cuing under blocked presentation conditions are discussed.In the present study, we used single-letter displays, that is, "empty" visual fields, to investigate central attentional effects on recognition accuracy in vision. In this context, attention can be operationally defined as the benefit in recognition or detection performance that occurs when subjects are cued in advance as to the location of a relevant stimulus (Prinzmetal, Presti, & Posner, 1986). Central attentional effects are demonstrated if benefits are obtained in an experimental setup that excludes directed eye movements.The information processing approach has provided clear evidence for central attentional effects with single-item displays in vision. In at least three types of task, clear benefits were obtained when subjects were given foreknowledge of where the single item was going to appear. Hoffman (1973, 1974) were the first to demonstrate faster reaction times in a letter-naming task, that is, in a suprathreshold recognition task, with latency as the dependent variable. Van der Heijden and Berland (1973) and Bashinski and Bacharach (1980), among others, demonstrated improved accuracy in tlash-and dotdetection tasks, that is, in threshold detection tasks, with accuracy as the dependent variable. Posner and his associates (see, e.g.,