زمان دوره از اثرات حواس پرتی دیداری و شنیداری در یک الگوی معین جدید متقابل

Abstract Vision often dominates audition when attentive processes are involved (e.g., the ventriloquist effect), yet little is known about the relative potential of the two modalities to initiate a “break through of the unattended”. The present study was designed to systematically compare the capacity of task-irrelevant auditory and visual events to withdraw attention from the other modality. Sequences of auditory and visual stimuli were presented with different amounts of temporal offset to determine the presence, strength, and time-course of attentional orienting and reorienting as well as their impact on task-related processing. One of the streams was task-relevant, while crossmodal distraction caused by unexpected events in the other stream was measured by impairments of behavioral task performance and by the N2, P3a, and reorienting negativity (RON) components of the event-related potential (ERP). Unexpected events in the visual modality proved to be somewhat more salient than those in the auditory modality, yet crossmodal interference caused by auditory stimuli was more pronounced. The visual modality was relatively constrained in terms of a critical time-range within which distraction effects could be elicited, while the impact of auditory stimuli on task-related processing extended over a longer time-range. These results are discussed in terms of functional differences between the auditory and visual modalities. Further applications of the new crossmodal protocol are deemed promising in view of the considerable size of the obtained distraction effects.

1. Introduction The capacity of human information processing is limited (Welford, 1952). It is thus of utmost importance to prioritize incoming information, allocating more attentional resources to stimuli that are relevant for the current goals of the organism. This process of selective attention goes at the expense of currently irrelevant stimuli (James, 1890). Because of these processing costs, attention must not be entirely selective: The organism needs to remain susceptible to new environmental events which might signal danger and thus require immediate behavioral adaptation. Attention shifts can occur within one modality, such as noticing a car horn when engaged in a conversation (intramodal shift within audition), or between modalities, e.g. noticing the brake lights of the car in front while concentrating on a radio announcement (crossmodal shift from audition to vision). As the choice of warning signals for car driving illustrates, it is crucial to know about the capacities of different sensory modalities to interfere with each other (e.g., Scott & Gray, 2008). The present study was designed to compare crossmodal attention shifts between vision and audition. The balance between focused attention and monitoring of the environment has been modeled in a class of distraction paradigms originally proposed by Escera, Alho, Winkler, and Näätänen (1998) in a crossmodal setting and in parallel by Schröger and Wolff (1998b) in an intramodal setting. In these paradigms, participants’ attention is focused on a primary task while events outside the task set are presented such that they belong to a frequent (standard) or to an infrequent (deviant) category. Based on the idea that any change in a sequence of repetitive stimuli is distracting, deviant events are evaluated in terms of their interference with task performance (for review, see Escera et al., 2000 and Escera and Corral, 2007). Typical findings (e.g., Schröger, Giard, & Wolff, 2000) include a behavioral impairment of task performance (increase of response times [RT] or error rates) and a characteristic series of event-related brain potential (ERP) components elicited by deviant relative to standard stimuli. The registration of the deviant event is signaled by negativities with fronto-central distribution occurring at 150–250 ms after deviation onset, consisting mainly in the mismatch negativity (MMN; Näätänen et al., 1978, Näätänen et al., 2007, Schröger, 2005 and Winkler, 2007) and N2b (Näätänen et al., 1982, Novak et al., 1990 and Patel and Azzam, 2005) components. A subsequent positive deflection at 300–400 ms after deviation onset (P3a component; Squires, Squires, & Hillyard, 1975; for reviews, see Friedman et al., 2001, Linden, 2005 and Polich, 2007) is considered to be a reflection of involuntary attention switching towards the new event (Escera et al., 2000 and Escera et al., 2001). Finally, attentional reorienting to the primary task has been related to the reorienting negativity (RON) component between 400 and 600 ms post-deviation (Schröger & Wolff, 1998a; for replication and elaboration, see e.g. Berti, 2008a, Berti, 2008b, Escera et al., 2001, Munka and Berti, 2006 and Yago et al., 2001). Along these lines, distraction has been investigated for auditory stimuli interfering with auditory primary tasks (Berti et al., 2004, Rinne et al., 2007, Roeber et al., 2003, Sabri et al., 2006 and Watkins et al., 2007) or with visual primary tasks (Escera et al., 2001, Muller-Gass et al., 2007, Munka and Berti, 2006, San Miguel et al., 2008, Yago et al., 2001 and Zhang et al., 2006). Attempts to transfer the paradigm to the visual modality (Berti and Schröger, 2004, Berti and Schröger, 2006, Grimm et al., 2009 and Kimura et al., 2008) have shown that distraction within vision is more elusive than within audition (for direct comparison, see Berti & Schröger, 2001). Very few studies looked at the influence of visual distracting events on auditory task performance (e.g., Alho et al., 1992, Astikainen et al., 2008 and Rees et al., 2001); they report electrophysiological signs of deviance processing, but no distraction effect on behavior (see also Boll & Berti, 2009, for an audiovisual task). The present study was designed to systematically compare crossmodal distraction between the visual and auditory modalities in the framework of attentional orienting and reorienting. The comparison aimed at the presence, amplitude, and time-course of behavioral and electrophysiological distraction effects. Stimulus sequences were composed of parallel auditory and visual streams presented simultaneously or with a constant amount of temporal offset. One of the streams was task-relevant, while the capacity of unexpected events in the other stream to withdraw attention from the primary task was investigated. Both streams followed a continuous roving-standard protocol (Cowan, Winkler, Teder, & Näätänen, 1993) with stimulus changes after every two to six repetitions. The task was defined as a discrimination of repetition versus change in the relevant stream; distracting events consisted in stimulus changes in the irrelevant stream. As crossmodal attentional links between vision and audition have been revealed in many studies for voluntary and involuntary spatial attention (e.g., Driver and Spence, 1998, Eimer and Driver, 2001 and Eimer and Schröger, 1998), crossmodal distraction is also expected in the present non-spatial distraction paradigm. Following previous studies (Berti and Schröger, 2001 and Boll and Berti, 2009), it was hypothesized that the auditory distracters would interfere with the primary visual task more than the visual distracters would interfere with the primary auditory task. Since visual and auditory information are processed at different speeds (e.g., Lewald and Guski, 2003, Nicolas, 1997 and Wallace et al., 1996), and since the two modalities may have specific time-courses of attention capture, distraction effects were compared for different amounts of temporal offset between streams. In order to exclude that asymmetries in crossmodal distraction effects might be due to the saliency of the changes per se, the processing of task-relevant changes was also compared between modalities.

5. Conclusions In summary, a new distraction paradigm was introduced that measures crossmodal interference with high sensitivity and provides a saliency control to render the comparison across modalities easier to interpret. The present results demonstrate that auditory and visual changes after short repetitive sequences are detected irrespective of their task-relevance and of their temporal relation to the information presented in the other modality. The impact of these changes on attentional orienting and behavior is, however, quite dependent on these factors, and especially so for unattended visual events, which elicit crossmodal interference only within a narrow time window. This qualifies previous reports of stronger distraction by auditory than visual stimuli by adding to them the temporal dimension as a critical factor for the bi-directionality of crossmodal interference.