Two experiments examined the speed-accuracy tradeoff for stimuli used by Martin (1979), some of which have a Stroop-like conflict between the relevant (to-be-judged) and the irrelevant aspect. Speed of transmitting information about a local aspect was significantly reduced when the irrelevant global aspect conflicted with the relevant local aspect, while speed of transmitting information about the global aspect was not affected when the irrelevant local aspect conflicted with the relevant global aspect. This result, when extrapolated to the accuracy level of an ordinary reaction-time task, fitted very well the reaction-time predictions of the global precedence model proposed by Navon (1977). However, other results were incongruent with the fundamental assumption of that model: that global features are accumulated with temporal priority over local features. The finding that, independently of speed, information transmission of the global aspect started later when the irrelevant local aspect was conflicting, corroborates Miller's (1981a) conclusion that global and local features are available with a similar time course. Global precedence is therefore a postperceptual effect; absence of interaction with 8-R compatibility suggested that it operated before the response selection stage. The term global dominance may be preferred, because it avoids the implication of prior availability for the global aspect. Furthermore, the possibility of whether Stroop conflict should be considered a necessary condition for global dominance is discussed.This article is concerned with the accumulation of information of a visual form and, in particular, with whether transmission of global information precedes transmission of local (detail) information. For the purpose of this paper, we conceive of perception as a process of gradual feature accumulation. Furthermore, in line with the continuous-flow model of Eriksen and Schultz (1978, 1979), we assume that a subject's response is based upon the amount of information accumulated at that particular instant. The ontogenesis of the percept ("Aktualgenese" in terms of the Leipzig School of Gestalt Psychology) will therefore be reflected by the response of the moment.For the global-to-local hypothesis, the distinction between global and local features is a basic one. As opposed to feature models in which global features are composites of local features (Gibson, 1969;Selfridge, 1959;Treisman & Gelade, 1980), the globalto-local hypothesis states that perception begins with a global whole to which local details are gradually added. According to the global precedence model, global and local features denote separate sets of features. Thus, global feature availability is not depen-
The effect of signal intensity upon reaction time (RT) was studied in three auditory RT tasks in which the signal was a tone of high or low frequency. Experiment I showed the well-known negative gradient with intensity of simple RT when the subject was instructed to ignore the frequency and give the same response to both tones. But when the subject had to discriminate the frequency in a choice RT task, the RT/intensity relationship appeared to be U-shaped. Experiment II showed that when the subject was required to make a response to one signal but withhold it for the other, a task which requires discrimination of the frequency of the tone but removes the necessity to choose between overt responses, no increase in RT at high intensities was obtained. The results indicate that it is the response choice stage rather than the stimulus encoding stage which is retarded at higher energy levels. Experiment I also demonstrated that visual and auditory leading signals have similar facilitating effects without affecting the RT/intensity relationships.
Confirming the findings in search tasks with letters and digits, the typical RT same < RTdiff result was obtained in a matching paradigm requiring the classification of geometrical stimuli that were given in pairs. The study supports a dual process model that is based on an identity reporter for the faster "same" response and a difference detector for the slower "different" responses, both operating with equal accuracy. Subjects appeared to perceive outline aspects of figures, formed by size and form, holistically. An internal characteristic, such as an interior line, was apparently processed as a separate attribute. However, the outlines of the stimulus configurations appeared to be much more salient and interfered with the judgment of the orientation of the interior line. Moreover, the latter stimulus aspect could be easily ignored as the task required.
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