Lag-1 sparing in the attentional blink with multiple RSVP streams

Abstract

When two targets are presented in a rapid stream of distractors, the accuracy of identifying the second target is impaired when the temporal lag between the targets is brief (attentional blink; AB). When the second target is presented immediately after the first target, the AB deficit is considerably reduced, a phenomenon called Lag 1 sparing. A recent study (Kristjansson & Nakayama, 2002) however, reported that Lag 1 sparing did not occur when multiple distractor streams were presented, al-though it had occurred in other studies (e.g., Peterson & Juola, 2000). The present study found that specific target attributes were the key for this inconsistency. When two targets in the same stream appear to be similar and are distinctive from the distractors, the first target is masked by the second. This masking of the first target increases the AB deficit, and Lag-1 sparing does not occur. Introduction We often encounter difficulties in processing two consecutive events in a brief interval. For example, when catching a cab, if we notice that the first approaching cab is occupied, it is highly likely that we will miss a second cab that appears immediately afterwards. Similarly, in the laboratory, when first and second targets (T1 and T2, respectively) are embedded in a rapid stream of distractors, T2 is frequently missed when the temporal lag between the two targets is short, although T1 is identified correctly. Successful T2 identification improves progressively as the temporal lag increases up to 700 ms. Poor identification of T2 in a rapid serial visual presentation (RSVP) is known as the attentional blink (AB; Raymond, Shapiro, & Arnell, 1992). The general consensus from studies of the AB is that this deficit derives from insufficient processing resources available for T2, because most of the available resources are used to process T1 when the temporal lag is brief (e.g., Shapiro, Arnell, & Raymond, 1997). As T1 processing releases more resources with increased lag time, T2 performance recovers. It is, however, not possible to explain the AB solely in terms of such resource depletion. Under the resource depletion scenario, T2 performance should be most impaired when T2 is presented directly after T1 (i.e., at Lag 1), but this was found to be the case in only approximately half of the experiments in the extant AB literature. In the remaining half, T2 performance at Lag 1 was not impaired. Potter, Chun, Banks, & Muckenhoupt (1998) termed this “Lag-1 sparing.” To understand this phenomenon, Visser, Bischof, & Di Lollo (1999) conducted a meta-analysis of previous AB studies. They defined Lag-1 sparing as the case in which identification of T2 at Lag 1 exceeded the lowest level of performance at the other lags by more than 5%. Visser, Bischof et al. (1999) found that changing spatial locations between T1 and T2 plays a critical role in determining whether Lag-1 sparing occurs. Their analysis indicated that T2 performance at Lag 1 is unimpaired when two targets appear in the same location. In contrast, when the two targets appear in different locations, Lag-1 sparing does not occur; the AB deficit is most severe at Lag 1. Based on this analysis, Visser, Zuvic, Bischof, & Di Lollo (1999) used a single RSVP stream and showed that Lag-1 sparing occurred when there was no spatial switching between the targets, but that it did not occur when there was spatial switching. However, when there are two or more RSVP streams, the situation is more complex. For example, Peterson & Juola (2000) used three concurrent RSVP streams and showed that Lag-1 sparing occurred when the two targets appeared in the same stream, but not when the targets appeared in different streams. On the other hand, Kristjansson & Nakayama (2002) used seven RSVP streams and reported that there was no Lag-1 sparing even when the two targets were presented in the same stream. This apparent inconsistency cannot be explained solely by the effect on Lag-1 sparing of spatial switching between the targets when using multiple RSVP streams, and the purpose of the present study is to determine the source of the inconsistency. We believe that it is important to understand the mechanisms for Lag-1 sparing, because it is one of the outstanding questions in AB studies (Shapiro et al., 1997) and because information about Lag-1 sparing will provide cues to characterize the temporal aspects of attention (Kawahara, 2003). The two studies that reported inconsistent results in Lag-1 sparing differ in three important ways. First, temporal parameters, especially stimulus-onset asynchrony (SOA) between the This is a preprint version of the article published at The Japanese Journal of Psychonomic Science