Some characteristics of selective attention in visual perception determined by vocal reaction time

Previous research had found that the accuracy with which an S could report an indicated letter or target in a briefly exposed multiletter display decreased as the number of irrelevant letters increased, and accuracy increased if the position of the target letter was indicated 150 msec before the display was presented. Iii the present experiment, these variables were reinvestigated using vocal reaction time as the dependent variable. An interpretation of the accuracy measures in terms of differential processing times was supported. The results of the two experiments were discussed in terms of a model of attentional selectivity.     

Do noise masks terminate target processing?

Much recent research in visual information processing has employed a methodology resting on the assumption that a noise mask following presentation of a target stimulus terminates processing of that target. In the absence of appropriate controls, such a methodology is viable only insofar as an erasure theory of masking is valid. However, the phenomena from which the erasure position has derived its strongest support have been subject to alternative theoretical explanations, the most general of which is that of temporal integration. The experiment reported here tested these alternatives. Twelve subjects served in a tachistoscopic study designed to determine whether the same noise field of dots could either erase a degraded target digit or facilitate target identification through temporal integration, under both forward and backward masking paradigms. This was found to be the case, and the results were interpreted as consistent with an integration theory of masking and as incompatible with an erasure conception. The results suggested that efforts to control target processing time through display of a visual noise pattern subsequent to target presentation are methodologically inadequate when devoid of some basic control operations.     

A forced-choice study of edge detectors in the human visual system

Psychophysical studies using masking procedures to investigate the possible existence of edge detectors in the human visual system have typically been flawed by methodological errors and omissions that make their findings uninterpretable. An example of such a study is given and evaluated, and a replication of that study, using a spatial forced-choice methodology, is reported in detail. The results of this replication are shown to contradict the critical findings of the earlier study; furthermore, it is suggested that any ambiguities in the results of this replication can be interpreted in terms of methodological and procedural factors, rather than in terms of higher-order neurological constructs. Finally, a further test of this methodological interpretation is proposed.     

Recognition memory and attentional selection: serial scanning is not enough

In two experiments, using memory sets of up to 10 letters, the response competition paradigm was employed to investigate the extent to which extraneous visual stimuli interfere with or affect the process of memory search. It was assumed that if selective attention could exclude the effect of noise letters from a Sternberg-type memory comparison process, then there would be an increase in intercept for the reaction time-set size functions but no increase in slope. This result was obtained. However, a large difference in response times to both positive and negative set targets was found when the accompanying noise letters indicated a competing response, as opposed to when they indicated the same response as the target. This implies rapid identification of the nature of both target and noise, independent of a serial comparison process. A modification of a dual process model (Juola, Fischler, Wood, & Atkinson, 1971) in which stimuli activate a familiarity value independent of memory search was suggested to account for these results.     

Comment on short-term variation in subjective sleepiness

Subjective sleepiness at different times is often measured in studies on sleep loss, night work, or drug effects. However, the context at the time of rating may influence results. The present study examined sleepiness throughout the day at hourly intervals and during controlled activities [reading, writing, walking, social interaction (discussion), etc.] by 10-min. intervals for 3 hr. This was done on a normal working day preceded by a scheduled early rising (to invite sleepiness) for six subjects. Analysis showed a significant U-shaped pattern across the day with peaks in the early morning and late evening. A walk and social interaction were associated with low sleepiness, compared to sedentary and quiet office work. None of this was visible in the hourly ratings. There was also a pronounced afternoon increase in sleepiness, that was not observable with hourly ratings. It was concluded that there are large variations in sleepiness related to time of day and also to context and that sparse sampling of subjective sleepiness may miss much of this variation.     

Safari to masking land: A hunt for the elusive U

Due to the theoretical interest in whether U-shaped visual masking functions are obtained when discrimination responses are required of the Ss, an attempt was made to replicate the Weisstein and Haber (1965) experiment. The attempt was unsuccessful. The results indicated that masking was uniform over a temporal range of approximately 50 msec. The possibility of individual differences in the shape of masking functions was investigated in two subsequent experiments with negative results. Overall, the results of the three experiments supported a temporal integration account of masking when assessed by detection or discrimination criteria. Some possible reasons for discrepancies with the Weisstein and Haber (1965) experiment were considered.     

“Subliminal cues” and the Müller-type illusion

Using the viewing box from a 2-field tachistoscope, feathers-arrows fr an 1 field were superimposed upon line-pairs from the other field to construct the Muller-Lyer illusion. 6 as were tested for the illusory effects under 4 conditions of feather-arrow detectability: (a) d′=O, (no luminance); (b) d′=.42; (c) d′=l.00; and (d) ′’=3.7. The length differences of lines of any given pair were 0 in., 1/64 in., 2/64 in., or 6/64 in. The illusion effect was observed when the featherarrow d’ equaled 3.7. No significant nor suggestive illusion effects were found for the other feather-arrow detectability conditions.     

Multiple-feature discrimination faster than single feature discrimination within the same object?

In the present study, we investigated whether judging the presence of multiple features within an object would be superior to judging the presence of only one feature. Feature discriminability and the number of features to discriminate within an object were varied. Specific features were judged as present or absent. Results showed that judging the presence of two or three features was faster than judging the presence of the less discriminable of these two or three features alone (multiple-feature benefits). These findings suggest that relevant features within an object activate (prime) a decision or response in a parallel, asynchronous fashion based on discriminability (Miller, 1982a). The ability of a response priming model, a response mapping model, and a template model to account for multiple feature benefits is discussed.     

N-channel tachistoscopes

Two 10-channel tachistoscopes are described. In one the optical system is based upon fiber optic light guides; channel and interchannel time control is provided by Tektronix pulse and waveform generators. In the other the optical system uses 10 8-mm variable power projector lens systems. Timing control is obtained from an Iconix timebase generator and preset counters. Two methods of programming the equipment are described and some experimental applications are considered.