Auditory Attentional Capture: Effects of Singleton Distractor Sounds Polly Dalton and Nilli Lavie University College London The phenomenon of attentional capture by a unique yet irrelevant singleton distractor has typically been studied in visual search. In this article, the authors examine whether a similar phenomenon occurs in the auditory domain. Participants searched sequences of sounds for targets defined by frequency, intensity, or duration. The presence of a singleton distractor that was unique on an irrelevant dimension (e.g., a low-frequency singleton in search for a target of high intensity) was associated with search costs in both detection and discrimination tasks. However, if the singleton feature coincided with the target item, search was facilitated. These results establish the phenomenon of auditory attentional capture. The brain receives an overwhelming amount of information from all of the senses at the same time. In order for people to respond to this stimulation appropriately, relevant stimuli must be selected for further processing while other, less relevant stimuli are ignored. Many studies have shown that people are able to focus attention efficiently on a subset of goal-relevant stimuli as long as the relevant and irrelevant stimuli differ from each other on the basis of a simple visual feature. For example, participants can be very efficient at searching for targets defined by curved features among nontargets with angular features (for review, see Duncan & Humphreys, 1989; Treisman, 1988). Although most of the nontar- gets in such search tasks can be ignored, recent research has suggested that if one of the nontargets is presented with a unique feature that makes it a singleton in the visual field (e.g., if it is red, whereas the other nontargets are green), it will typically interfere with search (e.g., Theeuwes, 1992). This interference will occur even though the distractor object is a singleton on a dimension that is never relevant to the task, suggesting that attention is captured by the singleton distractor rather than being voluntarily allocated to it. It seems likely that attention is tuned toward unique percep- tual objects (such as singletons) because such objects are different from the background and thus may indicate an important change in the environment. The phenomenon of attentional capture (AC) by an irrelevant singleton distractor has been studied extensively in visual search (for review, see Yantis, 2000). 1 The purpose of the present study was to examine whether a similar phenomenon can be found in the auditory domain. Because hearing is free from the spatial restric- tions of the other senses, one of its functions may be to act as an “early warning” system (e.g., Scharf, 1998) that monitors for changes in the environment. One might therefore expect that auditory attention would be tuned to unique distractor sounds (e.g., sounds with a singleton feature) and would thus be open to capture by such sounds, even when they were task-irrelevant. Previous Studies of Auditory Selective Attention Previous research has established that auditory attention, like visual attention, can focus on stimuli containing a particular (au- ditory) feature. For example, early studies using the dichotic listening technique found that participants could selectively attend to a channel defined by a certain auditory feature (e.g., words spoken by a female voice) while apparently ignoring the channel that did not share that feature (e.g., words spoken by a male voice; Cherry, 1953; Moray, 1959). However, these studies typically used complex semantic material (e.g., words or sentences), and the interpretation of their results was often complicated by the need to consider the effects of semantic priming on the extent to which irrelevant stimuli were ignored. For example, irrelevant but perti- nent words, such as a participant’s own name, were often recog- nized even in the unattended channel (for review, see Treisman, 1969). Clearer effects of focused attention on auditory perception have been demonstrated in studies using simpler auditory stimuli (e.g., pure tones) that assess performance on the basis of detection or discrimination reaction times (RTs) and accuracy. These studies have demonstrated, for example, that auditory detection or dis- crimination is facilitated when sounds are presented at expected rather than unexpected frequencies or intensities (e.g., Greenberg & Larkin, 1968; Luce & Green, 1978; Mori & Ward, 1991, 1992; Nosofsky, 1983; Schro ¨ger & Wolff, 1998; Tanner & Norman, 1 The phenomenon of AC in general has also been studied using the spatial-cuing paradigm (e.g., Jonides, 1980, 1981; Mu ¨ ller & Rabbitt, 1989; Remington, Johnston, & Yantis, 1992). However, the objects (cues) that have been shown to capture attention in these tasks were typically pre- sented on their own (cf. Folk & Remington, 1998; Folk, Remington, & Johnston, 1992; Folk, Remington, & Wright, 1994; Gibson & Kelsey, 1998; Johnson, Hutchison, & Neill, 2001) and therefore did not have to compete for attention with other objects. Thus, these studies cannot inform about the extent to which a singleton stimulus captures attention when it is in competition with multiple other stimuli, as in visual search. This research was supported by an Engineering and Physical Science Research Council (United Kingdom) studentship to Polly Dalton and Medical Research Council (United Kingdom) Grant G9805400 to Nilli Lavie. Correspondence concerning this article should be addressed to Polly Dalton or Nilli Lavie, Department of Psychology, University College London, Gower Street, London WC1E 6BT, United Kingdom. E-mail: polly.dalton@ucl.ac.uk or n.lavie@ucl.ac.uk Journal of Experimental Psychology: Copyright 2004 by the American Psychological Association, Inc. Human Perception and Performance 2004, Vol. 30, No. 1, 180 –193 0096-1523/04/$12.00 DOI: 10.1037/0096-1523.30.1.180 180