Task- and location-switching effects on visual attention

Abstract

In two experiments, we examined the effects of task and location switching on the accuracy of reporting target characters in an attentional blink (AB) paradigm. Single-character streams were presented at a rate of 100 msec per character in Experiment 1, and successive pairs of characters on either side of fixation were presented in Experiment 2. On each trial, two targets appeared that were either white letters or black digits embedded in a stream of black letter distractors, and they were separated by between zero and five items in the stream (lags 1-6). Experiment 1 showed that report of the first target was least accurate if it immediately preceded the second target and if the two targets were either both letters or both digits (task repetition cost). Report of the second target was least accurate if one or two distractors intervened between the two targets (the U-shaped AB lag effect) and if one target was a letter and the other a digit (task switch cost). Experiment 2 added location uncertainty as a factor and showed similar effects as Experiment 1, with one exception. Lag 1 sparing (the preserved accuracy in reporting the second of two targets if the second immediately follows the first) was completely eliminated when the task required attention switching across locations. Two-way additive effects were found between task switching and location switching in the AB paradigm. These results suggests separate loci for their attentional effects. It is likely that the AB deficit is due mainly to central memory limitations, whereas location-switching costs occur at early visual levels. Task-switching costs occur at an intermediate visual level, since the present task switch involved encoding differences without changes in stimulus-response mapping rules (i.e., the task was character identification for both letters and digits).

The attentional blink and lag 1 sparing are nonspatial

“…At the same time, the temporary deficit for T2, taken as indicative of an AB, still occurs. The conclusion has been that T1 causes a nonspatial AB for T2 (as demonstrated by the temporary deficit) but that lag 1 sparing may reflect an independent mechanism that is being camouflaged or abolished by the need to switch (Juola et al, 2004;Peterson & Juola, 2000;. However, this reasoning remains vulnerable to the possibility that not only the absence of lag 1 sparing, but also the entire cost for T2 is caused by spatial switching, while the AB itself is then still locked to the location of T1.…”

“…Yet, at the same time, one of the hallmarks of the AB, lag 1 sparing, dis- tasks for T1 and T2, in terms of both the stimulus properties the observer should look out for and the responses he or she should generate. Such task switches result in their own costs that may well add to the AB (Juola et al, 2004;. The interesting thing about the AB is that it occurs even when T1 and T2 are drawn from the same stimulus set and require the same type of response (e.g., Chun & Potter, 1995).…”

“…Another important conclusion from this study is that performance costs caused by spatial switches should be dissociated from performance costs caused by the AB proper (see also Juola et al, 2004;. This would imply that investigators need to take care not to attribute such switch costs to the AB itself.…”

The flexible focus: Whether spatial attention is unitary or divided depends on observer goals.

“…There are many reports in the literature that the magnitude of Lag-1 sparing is greater when T1 and T2 appear in the same spatial location (e.g., Du, Abrams, & Zhang, 2011;Jefferies & Di Lollo, 2009;Juola, Botella, & Palacios, 2004;Kawahara, 2002;Olivers, 2004;Visser, Bischof, & Di Lollo, 1999). The powerful effect of this factor can be seen in this study by considering Panels B and C of Figure 1: the magnitude of Lag-1 sparing is greater when the T2-pair appears in the same location as the T1-pair, regardless of whether the targets appear in-stream (filled circles in Panel B) or between-streams (empty circles in Panel C).…”

Beyond a mask and against the bottleneck: Retroactive dual-task interference during working memory consolidation of a masked visual target.

“…The answer is that this is highly unlikely because the latter first-target impairment is only found in combination with a sparing effect for the second target, and this combination of results is in turn only found when the temporal, and featural similarity of the two targets is high. To be precise, the results of studies on the attentional blink rarely show a first-target impairment if the two targets are presented at an SOA of more than 100 ms (e.g., Arnell & Jolicoeur, 1999;Nieuwenstein, Van der Burg, Theeuwes, Wyble, & Potter, 2009; but see Hommel & Akyurek, 2005, for an interesting exception), when they are drawn from different stimulus categories (e.g., Juola, Botella, & Palacios, 2004), or when they are presented in different modalities (e.g., Potter, Chun, Banks, & Muckenhoupt, 1998; see also Visser, Bischof, & Di Lollo, 1999). In contrast, the retroactive interference effect seen in the current experiments occurred across SOAs of up to 500 ms, it occurred after a mask, and it occurred across different combinations of modalities, target categories, and tasks.…”