Pierre Salamé

Disruption of short-term memory by unattended speech : Implications for the structure of working memory

A series of experiments studied the effect of unattended speech on immediate memory for visually presented digits. Memory performance showed clear impairment, with the degree of impairment being a function of the phonological similarity of the irrelevant words to the visually presented digits. In contrast, the semantic characteristics of the unattended speech did not influence performance. Requiring the subject to suppress articulation removed the disrupting effect of irrelevant speech. These results are interpreted in terms of two separate memory systems of which one relies on a phonological code. The system is accessible in two ways, through auditory presentation leading to obligatory registration of the material, or through an optional subvocal rehearsal process.

Effects of background music on phonological short-term memory

Immediate memory for visually presented verbal material is disrupted by concurrent speech, even when the speech is unattended and in a foreign language. Unattended noise does not produce a reliable decrement. These results have been interpreted in terms of a phonological short-term store that excludes non-speechlike sounds. The characteristics of this exclusion process were explored by studying the effects of music on the serial recall of sequences of nine digits presented visually. Experiment 1 compared the effects of unattended vocal or instrumental music with quiet and showed that both types of music disrupted STM performance, with vocal music being more disruptive than instrumental music. Experiment 2 attempted to replicate this result using more highly trained subjects. Vocal music caused significantly more disruption than instrumental music, which was not significantly worse than the silent control condition. Experiment 3 compared instrumental music with unattended speech and with noise modulated in amplitude, the degree of modulation being the same as in speech. The results showed that the noise condition did not differ from silence; both of these proved less disruptive than instrumental music, which was in turn less disruptive than the unattended speech condition. Theoretical interpretation of these results and their potential practical implications for the disruption of cognitive performance by background music are discussed.

Noise, unattended speech and short-term memory

Studies of ‘noise pollution’ have typically used unpatterned white noise. The present study compares the effect of noise with that of unattended speech. Three experiments required the immediate serial recall of sequences of nine visually presented digits accompanied by silence, noise or unattended speech in an unfamiliar language. Experiments 1 and 2 showed a clear effect of unattended speech at both 75dB(A) and 95dB(A), while unattended noise had no effect in either study. Experiment 3 used a separate groups design combining 95 dB(A) noise and quiet with instructions either to remain silent or to rehearse overtly. Overt rehearsal enhanced recall, while unattended noise again had no effect. It is suggested that noise does not interfere with short-term memory but that unattended speech does impair performance by disrupting the articulatory loop component of working memory. Implications for studies of ‘noise pollution’ are discussed.

Phonological factors in STM: Similarity and the unattended speech effect

Immediate memory for sequences of 5,6, 7, or 8 phonologically similar or dissimilar consonants was studied using visual presentation accompanied by silence or continuous speech in an unfamiliar language, Arabic. There were significant effects of list length, phonological similarity, and unattended speech, and significant interactions between similarity and unattended speech and between similarity and list length. The interactions are shown to stem primarily from the absence of a decrement due to phonological similarity at List Length 8. It is suggested that this absence is attributable to a strategy of abandoning phonological coding when performance drops below some minimum level.

The unattended speech effect: perception or memory?

Broadbent (1983) has suggested that the influence of unattended speech on immediate serial recall is a perceptual phenomenon rather than a memory phenomenon. In order to test this, subjects were required to classify visually presented pairs of consonants on the basis of either case or rhyme. They were tested both in silence and against a background of continuous spoken Arabic presented at 75 dB(A). No effect of unattended speech was observed on either the speed or accuracy of processing. A further study required subjects to decide whether visually presented nonwords were homophonous with real words. Again, performance was not impaired by unattended speech, although a clear effect was observed on an immediate serial memory task. Our results give no support to the perceptual interpretation of the unattended speech effect.

The effects of irrelevant speech on immediate free recall

Immediate ordered recall is strongly disrupted by concurrent irrelevant speech even when the speech is unfamiliar to the subject. This effect has been replicated in many experiments with immediate serial recall. In the present study, we examined the effect of speech on immediate free recall of lists of 16 words presented visually. No impairment in the speech condition was found in comparison with the control, but the same subjects showed a consistent impairment of immediate serial recall under speech in a separate experiment. It is concluded that irrelevant speech impairs immediate phonological memory but does not disrupt performance on either the long- or short-term components of the standard verbal free recall task.

Human core temperature minimum can be modified by ambient thermal transients

By using slow linear thermal transients (+/- 0.025 degree C/min) of reduced amplitude (+/- 3 degrees C around thermoneutrality), we were able to advance the minimum of human internal temperature (Ti) during nocturnal sleep. During experimental night the minimum of esophageal (Tes) and rectal (Tre) temperature were respectively advanced by 1.6 h (P < 0.01) and 2.6 h (P < 0.001) in comparison to reference night spent at thermoneutrality. It must be emphasized that the provoked advance of nocturnal Ti minimum was not accompanied by any change in sleep latency, efficiency, SWS and REM sleep percentages. The result shows that appropriate ambient temperature transient changes could be used to modify the course of human Ti one of the major biological rhythms usually considered as resistant to sleep-wake rhythm manipulation.

Effects of sleep inertia on cognitive performance following a 1-hour nap

Abstract This study investigated the effects of a 1-h nap on subsequent performance in spatial memory (SM) and logical reasoning (LR) tasks. The objective was to evaluate the duration of the effects of sleep inertia (SI). The performance was measured in two independent groups of subjects. The 1-h nap took place at 00:00 h in group 1 and at 03:00 h in group 2. In each task, the experimental design comprised one no-nap condition in which subjects had no sleep before the night tests, and a nap condition that comprised the 1-h nap followed by the test sessions. To measure the duration of SI effects, the subjects were tested in two 30-min sessions and the data in each session were analysed in sub-units of time of 3 min each. In each task the results showed no effects on accuracy, and no circadian effects of napping were found. In each task, analyses of pooled data of the two groups showed that the performance in the 1-h nap condition exhibited significant reductions of speed immediately following awakening, wh...