Time course of visual information utilization during fixations in reading

College students read short texts from a cathode-ray tube as their eye movements were being monitored. During selected fixations, the text was briefly masked and then it reappeared with one word changed. Subjects often were unaware that the word had changed. Sometimes they reported seeing the first presented word, sometimes the second presented word, and sometimes both. When only one word was reported, two factors were found to determine which one it was: the length of time a word was present during the fixation and the predictability of a word in its context. The results suggested that visual information is utilized for reading at a crucial period during the fixation and that this crucial period can occur at different times on different fixations. The pattern of responses suggested that the first letter of a word is not utilized before other letters and that letters are not scanned from left to right during a fixation.     

Factors influencing readability of rapidly presented text segments

Experiment 1 compared paragraph comprehension for texts shown either as normal pages on a computer terminal screen or as rapid serial visual presentations (RSVPs) of small text segments to a common location. Over several days of practice, reading comprehension was equivalent in the normal presentation mode and the RSVP format. When successive RSVP segments contained some information in common, to mimic the experience of successive parafoveal and foveal views of words in normal reading, comprehension was somewhat worse than when successive segments contained no overlapping information. Experiment 2 used a variety of segment size and segment duration combinations to investigate the optimal means of presenting text in the RSVP format. Across a variety of presentation rates and text difficulties, comprehension was maximal for segments averaging about 12 character spaces in length. In Experiment 3, texts were divided into short idea units or into random segments of equal average length. Comprehension was shown to be greater in the structured condition than in the random condition. An optimal means of presenting text in the RSVP format could be superior to normal presentation methods for reading and other text-processing tasks.     

Two stages in postcategorical filtering and selection

Memory &; Cognition - In a modified Stroop paradigm, Kahneman and Henik (1981) varied the spatial location of incompatible color words in relation to the position of the ink color to be named. A...     

Comments on Hughes and Sussman''s time-sharing study of cerebral laterality in language-disordered and normal children

M. Hughes and H. M. Sussman (1983, Brain and Language, 19, 48-64) suggest that the time-sharing paradigm "does not serve as an adequate behavioral index for language lateralization in children." The merits of this conclusion are considered and general interpretative issues regarding manual interference in dual-task/time-sharing studies are discussed.     

Auditory perception of breaking and bouncing events: a case study in ecological acoustics

The mechanical events of bouncing and breaking are acoustically specified by single versus multiple damped quasi-periodic pulse patterns, with an initial noise burst in the case of breaking. Subjects show high accuracy in categorizing natural tokens of bouncing and breaking glass as well as tokens constructed by adjusting only the temporal patterns of components, leaving their spectral properties constant. Differences in average spectral frequency are, therefore, not necessary for perceiving this contrast, though differences in spectral consistency over successive pulses may be important. Initial noise corresponding to glass rupture appears unnecessary to categorize breaking and bouncing. The data indicate that higher order temporal properties of the acoustic signal provide information for the auditory perception of these events.     

Integrating pictorial information across eye movements

Six experiments are reported dealing with the types of information integrated across eye movements in picture perception. A line drawing of an object was presented in peripheral vision, and subjects made an eye movement to it. During the saccade, the initially presented picture was replaced by another picture that the subject was instructed to name as quickly as possible. The relation between the stimulus on the first fixation and the stimulus on the second fixation was varied. Across the six experiments, there was about 100-130 ms facilitation when the pictures were identical compared with a control condition in which only the target location was specified on the first fixation. This finding clearly implies that information about the first picture facilitated naming the second picture. Changing the size of the picture from one fixation to the next had little effect on naming time. This result is consistent with work on reading and low-level visual processes in indicating that pictorial information is not integrated in a point-by-point manner in an integrated visual buffer. Moreover, only about 50 ms of the facilitation for identical pictures could be attributed to the pictures having the same name. When the pictures represented the same concept (e.g., two different pictures of a horse), there was a 90-ms facilitation effect that could have been the result of either the visual or conceptual similarity of the pictures. However, when the pictures had different names, only visual similarity produced facilitation. Moreover, when the pictures had different names, there appeared to be inhibition from the competing names. The results of all six experiments are consistent with a model in which the activation of both the visual features and the name of the picture seen on the first fixation survive the saccade and combine with the information extracted on the second fixation to produce identification and naming of the second picture.     

Awareness of the response after feedback training for changes in heart rate and sudomotor laterality

What is the relation between the ability to control visceral responding on a biofeedback task and the ability to report behaviors actually contributing to this performance? Subjects received biofeedback training for unidentified visceral responses and then gave written reports about what they had done to control the feedback displays. Independent judges were given these reports and, on the basis of knowledge about activities known to contribute to visceral activity, were asked to determine the visceral responses for which the subjects had been trained. The reports of subjects who succeeded at bidirectional control of heart rate (Experiment 1) or sudomotor laterality (Experiment 2) showed awareness of behaviors related to feedback as assessed by this procedure, whereas the reports of subjects who failed at bidirectional control did not. Subsequent experiments indicated that these results did not depend on a learning strategy that might have been specific to the initial studies. These findings call into question the view that people are unaware of what they have done to produce the response after training on biofeedback tasks. Earlier studies reporting lack of awareness in biofeedback are discussed in light of factors that affect the measurement of biofeedback learning and response awareness.     

How normal and retarded individuals monitor and regulate speed and accuracy of responding in serial choice tasks

These experiments investigate whether or not differences in the way that retarded and nonretarded individuals monitor and regulate speed and accuracy of responding contribute to the slower and more variable performance of retarded subjects on choice reaction time (RT) tasks. Rabbitt (1979, 1981) suggested that efficient choice RT performance is mediated by subjects tracking increasingly faster RT bands on successive trials until, by making and recognizing errors, they discover those very fast RT levels that should be avoided and those safe bands, just above typical error levels, that should be tracked. Experiments 1A and 1B established that most retarded subjects detect their errors as efficiently as nonretarded controls, a finding that excludes the possibility that retarded subjects do not monitor accuracy efficiently but achieve comparable levels of accuracy by consistently responding within very slow RT bands that minimize likelihood of errors. Experiment 2 showed that while a qualitatively similar trial-by-trial tracking mechanism mediates the performance of both groups, retarded subjects are less efficient at constraining RTs within very fast, but safe, bands. Increasing error probabilities at longer RTs suggest that momentary fluctuations in stimulus discriminability and/or attention are factors affecting RT variability in retarded subjects. The RT patterns for various sequences of correct responses initiated and terminated by errors suggest that the effective past experience (EPEX) guiding trial-by-trial RT adjustments of retarded subjects is short and inadequate, and it was argued that this can account for much of the remaining RT variability contributing to retarded-nonretarded differences. Not only does a short EPEX increase variability by giving rise to long error-free sequences of slower than average RT but also, when combined with occasional specified random fluctuations, it suggests why retarded subjects can achieve, but not sustain, RT levels maintained by nonretarded subjects.