Component Problems in Dichotic Listening

Lexical and Grammatical Processing of Unshadowed Messages: A Re-Examination of the Mackay Effect

Mackay (1973) claimed to have provided evidence that subjects could process the grammatical structure and lexical content of nonshadowed messages. In the present study, it was found impossible to repeat Mackay's findings when controls for several factors that had been ignored in Mackay's study were employed. Subsequent experiments indicated that two major factors contributing to Mackay's results were that he had a gap between sentences in his experiment and that the nonshadowed material came out of a background of silence. Both of these probably enabled subjects to switch attention to the nonshadowed material without disruption of shadowing performance.

On determining what is unconscious and what is perception

In sum, dichotic listening tasks are appropriate for testing whether perception requires attention. The separate issue of the possible presence of perception that can never be brought under the spotlight of awareness should indeed be investigated by paradigms such as masking. However, the ultimate criterion for availability to awareness must be phenomenal experience. The discrepancy between thresholds of different perceptual indices is an important empirical finding, but its theoretical interpretation is not straightforward. In addition, it is suggested that we worry about the possibility that so-called indirect evidence reflects side effects of perceptual processing rather than the contents of its final product. In that case, what are being observed are vestiges of the processing of stimuli that do not make it to awareness. Whether those stimuli are below the threshold for overt response is an open question.

Semantic activation without conscious identification in dichotic listening, parafoveal vision, and visual masking: A survey and appraisal

When the stored representation of the meaning of a stimulus is accessed through the processing of a sensory input it is maintained in an activated state for a certain amount of time that allows for further processing. This semantic activation is generally accompanied by conscious identification, which can be demonstrated by the ability of a person to perform discriminations on the basis of the meaning of the stimulus. The idea that a sensory input can give rise to semantic activation without concomitant conscious identification was the central thesis of the controversial research in subliminal perception. Recently, new claims for the existence of such phenomena have arisen from studies in dichotic listening, parafoveal vision, and visual pattern masking. Because of the fundamental role played by these types of experiments in cognitive psychology, the new assertions have raised widespread interest.

The purpose of this paper is to show that this enthusiasm may be premature. Analysis of the three new lines of evidence for semantic activation without conscious identification leads to the following conclusions. (1) Dichotic listening cannot provide the conditions needed to demonstrate the phenomenon. These conditions are better fulfilled in parafoveal vision and are realized ideally in pattern masking. (2) Evidence for the phenomenon is very scanty for parafoveal vision, but several tentative demonstrations have been reported for pattern masking. It can be shown, however, that none of these studies has included the requisite controls to ensure that semantic activation was not accompanied by conscious identification of the stimulus at the time of presentation. (3) On the basis of current evidence it is most likely that these stimuli were indeed consciously identified.

The Maltese cross: A new simplistic model for memory

This paper puts forward a general framework for thought about human information processing. It is intended to avoid some of the problems of pipeline or stage models of function. At the same time it avoids the snare of supposing a welter of indefinitely many separate processes. The approach is not particularly original, but rather represents the common elements or presuppositions in a number of modern theories. These presuppositions are not usually explicit, however, and making them so reduces the danger of slipping back into earlier modes of thought.

The key point is to distinguish between persisting representations and the processes that translate one representation into another. Various classes or groups of persisting representations can be distinguished by the experimental treatments that interfere with them. In particular, there now seem to be several kinds of short-term or temporary storage, different from each other as well as from longterm memory; the translating processes also have several different modes or kinds. A particularly important aspect of the current position is that a model of this general type no longer requires some external agent to direct and control long sequences of behaviour.

Modality effects and the structure of short-term verbal memory

The effects of auditory and visual presentation upon short-term retention of verbal stimuli are reviewed, and a model of the structure of short-term memory is presented. The main assumption of the model is that verbal information presented to the auditory and visual modalities is processed in separate streams that have different properties and capabilities. Auditory items are automatically encoded in both the A (acoustic) code, which, in the absence of subsequent input, can be maintained for some time without deliberate allocation of attention, and a P (phonological) code. Visual items are retained in both the P code and a visual code. Within the auditory stream, successive items are strongly associated; in contrast, in the visual modality, it is simultaneously presented items that are strongly associated. These assumptions about the structure of short-term verbal memory are shown to account for many of the observed effect of presentation modality.