PubMed · 6869474
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R W Lingua, S Azen. 1983. Succinyldicholine and the basic ocular deviation.. https://doi.org/10.1016/0002-9394(83)90478-6
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Four experiments are reported in which the subjects had to respond to a target that masked a preceding prime via metacontrast masking. In one part of Experiment 1, the subjects discriminated the target's shape (square or diamond) by a motor-choice reaction, and in another part they had to respond with a simple reaction. The prime was neutral (circular) with respect to the target's shape. The data showed a facilitation effect. In both tasks the reaction time was reduced by the masked prime. However, the reduction was more pronounced with simple reaction than with choice reaction. In the other experiments, additional primes were used with the same angular shapes as the targets. In Experiments 2 and 3, after discriminating the target's shape by a choice reaction, the subjects had to judge the prime's shape in a signal-detection task. While neither the d' value for discriminating the angular primes from the circular ones (Exp. 2) nor the d' value for distinguishing between the angular primes (Exp. 3) was different from zero, the choice-reaction data showed a congruency effect. With a congruent prime (i.e., a prime that had the same shape as the target), the reaction times were reduced. With an incongruent prime, the reaction times grew. In Experiment 4 the errors were investigated. The facilitation effect was present in the RT, but not in the number of errors, whereas the congruency effect was present in the number, but not in the RT of errors. While the facilitation effect can be attributed either to an unspecific activation by the masked prime or to an influence of the prime on attentional processes, the congruency effect can be explained by the assumption that the masked prime directly activates the specific response, which corresponds to the prime's shape.
A photic stimulus flashed just before a saccade in the dark tends to be mislocalized in the direction of the saccade. This mislocalization is not only perceptual; it is also expressed by errors of ocular targeting. A particular situation arises if the point of light is flashed twice at the same place, the second time, just before a saccade. The point of light may appear at two different places even though neither the site of its retinal image nor the direction of gaze change between the flashes. Experiments were run on five human subjects, head fixed in the dark, with flashes repeated at the site of the saccade goal or at the initial point of fixation. In both cases, the test stimulus was mislocalized. However, its apparent displacement never produced the perception of a streak. Streaks were reported only when there was an actual stimulus movement on the retina (e.g. by flashing the stimulus during the saccade). Mislocalization did not occur if the two flashes were not separated by a dark interval. This implies that, as long as a steady stimulus remains continually visible, there is no updating of the internal representation of eye position assumed to be used for stimulus localization.
Subjects' eye movements were measured whilst they read and performed lines of music consisting of rhythmic information only, in conventional musical notation. The relationship between the spatial pattern of the notes displayed and of the fixations made in reading them is stochastic, and similar to that in ordinary reading, but with a tendency to fixate salient details of the notation such as notes and barlines rather than the spaces in between. Shorter notes are less likely to be fixated than longer ones, and this is determined by their performance length rather than their visual appearance. Despite the timing constraints imposed by the music, the time of execution of individual saccades appears to be entirely unrelated to the time of the execution of elements of the performance itself. However, as the tempo of performance of a given piece of music is increased, the average time between saccades decreases but their mean amplitude increases. These observations suggest a new model of the oculomotor and perceptual processes involved, in which an central, iconic representation of the fixated image is internally scanned and interpreted to a given criterion of accuracy, the scan ending when this criterion cannot be reached, and this end-point determining the position of the next fixation. It is proposed that the fullness of the buffer between the perceptual and motor processes determines the strictness of the criterion which is adopted, and hence the amplitude and timing of the eye movements.