Restricted Attentional Capacity within but Not between Sensory Modalities: An Individual Differences Approach

Sander Martens,Manasa Kandula,John Duncan

doi:10.1371/journal.pone.0015280

Abstract

BackgroundMost people show a remarkable deficit to report the second of two targets when presented in close temporal succession, reflecting an attentional blink (AB). An aspect of the AB that is often ignored is that there are large individual differences in the magnitude of the effect. Here we exploit these individual differences to address a long-standing question: does attention to a visual target come at a cost for attention to an auditory target (and vice versa)? More specifically, the goal of the current study was to investigate a) whether individuals with a large within-modality AB also show a large cross-modal AB, and b) whether individual differences in AB magnitude within different modalities correlate or are completely separate.Methodology/Principal FindingsWhile minimizing differential task difficulty and chances for a task-switch to occur, a significant AB was observed when targets were both presented within the auditory or visual modality, and a positive correlation was found between individual within-modality AB magnitudes. However, neither a cross-modal AB nor a correlation between cross-modal and within-modality AB magnitudes was found.Conclusion/SignificanceThe results provide strong evidence that a major source of attentional restriction must lie in modality-specific sensory systems rather than a central amodal system, effectively settling a long-standing debate. Individuals with a large within-modality AB may be especially committed or focused in their processing of the first target, and to some extent that tendency to focus could cross modalities, reflected in the within-modality correlation. However, what they are focusing (resource allocation, blocking of processing) is strictly within-modality as it only affects the second target on within-modality trials. The findings show that individual differences in AB magnitude can provide important information about the modular structure of human cognition.

Highlights

Limitations on divided attention across different modalities have been the subject of much controversy
When the two targets were presented in different modalities, any temporal restrictions in attentional capacity as reflected in the attentional blink (AB) disappeared
A repeated measures analysis of variance (ANOVA) of T1 performance with condition (VV, auditory within-modality (AA), VA, AV) and lag (1, 2, 3, 4, 7, 9) as a within-subjects factor revealed a significant effect of lag, F(5, 200) = 3.39, MSE = 50.55, p,.01, g2p = .08, such that performance was lower at lag 1 than at the other lags

Summary

Introduction

Limitations on divided attention across different modalities have been the subject of much controversy. In hundreds of experiments it has been shown that when two targets are presented within a rapid stream of non-targets (i.e., distractors), most individuals demonstrate a profound difficulty to report the second target (T2) when presented within 200–500 ms after the first (T1) This interference effect, which is referred to as the attentional blink (AB) in analogy to eye blinks [17], is very robust and can be obtained under a variety of task conditions, using for instance alphanumeric stimuli [18], words [19], pictures [20], and with auditory [16] or tactile stimuli [21].

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Conclusion