Can simultaneous speech stimuli be classified in parallel?

Reaction times to detect a known or unknown digit in paired or single auditory test stimuli were measured. The results suggest that in classification or matching tasks with stimuli belonging to separate verbal classes, parallel or selective processing may be possible. There was no interaction of type of task (classify vs match) with either dichotic vs mixed monaural presentation, or pairs vs single stimuli, or negative vs positive responses. An attempt was made to suggest the separate processing stages underlying performance in this task.     

Selective attention and cerebral dominance in perceiving and responding to speech messages

The effect of attention on cerebral dominance and the asymmetry between left and right ears was investigated using a selective listening task. Right handed subjects were presented with simultaneous dichotic speech messages; they shadowed one message in either the right or left ear and at the same time tapped with either the right or the left hand when they heard a specified target word in either message. The ear asymmetry was shown only when subjects' attention was focused on some other aspect of the task: they tapped to more targets in the right ear, but only when these came in the non-shadowed message; they made more shadowing errors with the left ear message, but chiefly for non-target words. The verbal response of shadowing showed the right ear dominance more clearly than the manual response of tapping. Tapping with the left hand interfered more with shadowing than tapping with the right hand, but there was little correlation between the degree of hand and of ear asymmetry over individual subjects. The results support the idea that the right ear dominance is primarily a quantitative difference in the distribution of attention to left and right ear inputs reaching the left hemisphere speech areas. This affects both the efficiency of speech perception and the degree of response competition between simultaneous verbal and manual responses.     

The effect of warning interval on the electric phosphene and auditory thresholds

Using different warning signals and threshold stimuli, the thresholds, as determined by a method of limits, were found to rise monotonically as the interval between warning signal and threshold stimulus increased from I to 9 sec. It was found that the variability of the threshold did not increase as the threshold increased. Similar results were obtained for phosphene and auditory thresholds and with visual and auditory warnings; therefore the effect was considered to be central. Motokawa's finding of a minimum in the phosphene threshold 2 sec. after a flash of white light was not repeated. The rise in threshold was not obtained when the warning intervals were randomized and so seemed to depend on the use of fixed warning intervals. A model was developed relating threshold level to accuracy of anticipation of the end of the warning interval.     

Does a color difference between parts impair the perception of a whole? A similarity between simultanagnosia patients and healthy observers

In three experiments, participants decided whether a Star of David shape was present among distractors. Although the participants were instructed to ignore the colors in the display, detection was slower when each triangle of the Star of David was printed in a different color than when the Star of David was printed in a uniform color or when each triangle was in two colors. Extending the object file theory, we suggest that when the parts of an object are distinguished by a color difference and are perceived as separate objects, the perception of the whole object, which is composed of these same parts, is damaged. One interpretation within object file theory is that when the visual system represents the location of a complex object as occupied by identity tags for its different parts, it cannot also link the same location to the identity of the complex object. A new object file must then be created.     

Dividing attention across feature dimensions in statistical processing of perceptual groups

Statistical processing has been shown in the perception of several visual dimensions, including size, speed, direction of motion, and orientation. Chong and Treisman (2005) found no decrement when people simultaneously averaged two sets on a single dimension, size. What happens when attention is divided between different dimensions? In two experiments, we investigated judgments of mean size and speed, either within the same objects or in two separate sets. In a third, we examined judgments of mean size and orientation in two different sets. All three experiments suggest a decrement in performance when attention is shared between two dimensions, especially when they are carried by two different sets of objects.     

Perceiving and re-perceiving objects.

A number of experiments exploring priming effects and automatization in the perception of novel objects are described, and a framework for understanding the benefits and costs of re-perceiving previously seen objects is proposed. The suggestion is that perceiving an object creates a temporary representation in an object file that collects, integrates, and updates information about its current characteristics. The contents of an object file may be stored as an object token and retrieved next time the object appears. This facilitates its re-perception when all of the attributes match and may impair it if some are changed. Thus, the world molds our minds to capitalize on earlier experiences but at the same time leaves us able readily to detect and represent any novel or unexpected objects and events.     

A theory of criterion setting: an alternative to the attention band and response ratio hypotheses in magnitude estimation and cross-modality matching

The attention band and response ratio hypotheses of Green and Luce (1974) and Luce and Green (1974) are discussed and some difficulties are noted. An alternative hypothesis is put forward. This is based on a Thurstonian model for magnitude estimation in which the presented stimulus intensities are subjected to a logarithmic transformation. Response criteria are then applied to the resulting quantities to select corresponding responses. The setting and maintenance of these response criteria are accounted for by a theory of criterion setting previously developed by the senior author (Treisman & Williams, 1984). A similar model is developed for cross-modality matching, and it is shown that these models can predict the V pattern for the coefficient of variation of response ratios, can predict the inverted V pattern for correlations between successive responses, and can account for some of the difficulties found in the literature.     

Book reviews

BEIDLER, L. M. (ED.). Handbook of Psysiology. Vol. IV. Berlin: Springer- Verlag. 1971. Pp. 518. $ 47.50.

MAUSNER, B. AND PLATT, E. Smoking: A Behavioural Analysis. Oxford: Pergamon Press 1971. Pp. 238. £ 5.50.

M. H. APPLEY (Ed.). Adoptation-Level Theory. Academic Press: New York and London. 1971. £ 6.05.     

Illusory conjunctions in the perception of objects

In perceiving objects we may synthesize conjunctions of separable features by directing attention serially to each item in turn (A. Treisman and G. Gelade, Cognitive Psychology, 1980, 12, 97–136). This feature-integration theory predicts that when attention is diverted or overloaded, features may be wrongly recombined, giving rise to “illusory conjunctions.” The present paper confirms that illusory conjunctions are frequently experienced among unattended stimuli varying in color and shape, and that they occur also with size and solidity (outlined versus filled-in shapes). They are shown both in verbal recall and in simultaneous and successive matching tasks, making it unlikely that they depend on verbal labeling or on memory failure. They occur as often between stimuli differing on many features as between more similar stimuli, and spatial separation has little effect on their frequency. Each feature seems to be coded as an independent entity and to migrate, when attention is diverted, with few constraints from the other features of its source or destination.     

Semantic processing in dichotic listening? A replication

This experiment explores semantic processing of one message while another is attended to and shadowed. It was an attempt to replicate and clarify an earlier finding by Lewis (1970). Like Lewis, we found that mean shadowing latency was increased when a synonym of the shadowed word coincided with it on the unattended channel. However, this occurred only with synonyms in an early list position and appeared to affect only a small proportion of trials. The implications of this and other recent findings for theories of selective listening are discussed.