Memory in a bisensory selective attention task

Theories of selective attention differ with respect to the amount of processing alleged to be undergone by non-attended material. “Early” selection theorists have argued that only physical properties of the non-attended material are extracted whereas “late” selection theorists have claimed that all inputs are fully analysed with selection taking place at the output stage.

Recent attempts to investigate these theories have investigated memory for non-attended material. The present experiment was designed to investigate memory for physical and semantic properties of non-attended material. Subjects shadowed words presented aurally and were tested for recall of simultaneously presented visual material. The visual stimuli consisted of either patches of colour or the names of those colours, the former containing only physical properties and the latter requiring semantic processing. Different shadowing conditions were employed in which subjects shadowed either colour names or unrelated words.

Recall of the colours was found to be superior to recall of the colour names and recall of both classes of material was found to be superior when subjects shadowed colour names than when they shadowed unrelated words. The results were interpreted as providing evidence for the existence of a post-iconic visual memory store based primarily on physical properties of the input.

Visual and auditory autokinesis

Two experiments demonstrate continuity in autokinetic movement of visual and auditory stimuli. In one experiment, the trial-to-trial correlations of duration of autokinetic movement were almost as large between modalities (correlating responses to the auditory stimulus with those to the visual) as they were within a given modality. In the second experiment, manipulation of instructions produced equivalent effects upon autokinesis in the two modalities. Introducing extraneous asymmetric stimulation had no effect in either modality. Current theories about autokinesis are largely mode specific; the results of these experiments suggest that central determinants also contribute strongly to the effect.

Auditory and phonetic memory codes in the discrimination of consonants and vowels

Recognition memory for consonants and vowels selected from within and between phonetic categories was examined in a delayed comparison discrimination task. Accuracy of discrimination for synthetic vowels selected from both within and between categories was inversely related to the magnitude of the comparison interval. In contrast, discrimination of synthetic stop consonants remained relatively stable both within and between categories. The results indicate that differences in discrimination between consonants and vowels are primarily due to the differential availability of auditory short-term memory for the acoustic cues distinguishing these two classes of speech sounds. The findings provide evidence for distinct auditory and phonetic memory codes in speech perception.