领域：学术论文 · 社会科学

We spend a lot of time searching for things. If we know what we are looking for in advance, a memory representation of the target will be created to guide search. But if the identity of the search target is revealed simultaneously with the presentation of the search array, is a similar memory representation formed? In the present study, 96 observers determined whether a central target was present in a peripheral search array. The results revealed that as long as the central target remained available for inspection (even if only in iconic memory), observers reinspected it after each distractor was checked, apparently forgoing consolidation of the target into working memory. The present findings challenged the assumption that evaluating items in a search array must involve comparison with a template in working memory.

Palmer (1995) proposed that visual search involves four processing stages: preselection, selection, postselection, and decision. Whereas many efforts have been made to examine the mechanisms of the first three stages (e.g., Lavie, Hirst, De Fockert, & Viding, 2004; Treisman & Gelade, 1980; Wolfe, 1994), little is known about the decision stage. The decision stage involves comparisons between the attentional template (a mental representation of the target) and items in the search array (to determine whether the item is a target). Standard theories of attention assume that the template comparison occurs in working memory (Bundesen, 1990; Duncan & Humphreys, 1989; Treisman & Gelade, 1980). Consistent with this assumption, evidence demonstrates that the attentional template may be stored in working memory during the initial configuration of attentional control settings (Carlisle, Arita, Pardo, & Woodman, 2011; Woodman & Arita, 2011).

However, consolidating information into working memory is time consuming (Jolicœur & Dell’Acqua, 1998; Vogel, Woodman, & Luck, 2006) and may sometimes be inefficient. It has been suggested that the locations of visited distractors may not be remembered during visual search (Horowitz & Wolfe, 1998) and that the attributes of a just-attended object may not always be retained in working memory (Chen & Wyble, 2015). Moreover, the speed of search is faster than the speed of memory consolidation; for example, searching for a color among a group of distinctive colors can be as fast as 10 ms per item (Olds, Cowan, & Jolicoeur, 1999), but consolidating color information into working memory takes about 50 ms per item (Vogel et al., 2006). These findings suggest that properties of the search array need not be consolidated into working memory. Then what about the target itself?

In the present study, we investigated whether target identity is stored in working memory when the identity of the target is both revealed simultaneously with the search array and remains available for inspection during search. Objects are identified and recognized more rapidly than information is consolidated into working memory (Jolicœur & Dell’Acqua, 1998; Potter, 1976; Thorpe, Fize, & Marlot, 1996). If the target identity is available for inspection only while the search array is present, observers may proceed immediately to search without stopping to consolidate the target in working memory. One way to avoid the need for consolidation is to revisit the target during search.

To test the above hypothesis, we first compared search efficiency in a target-in-memory condition (in which the target identity has to be stored in working memory) with search efficiency in a target-on-screen condition (in which the target identity is shown simultaneously with the search array and remains available during the search). Wolfe, Horowitz, Kenner, Hyle, and Vasan (2004) showed that when the target identity is revealed (as briefly as 50 ms) before the presentation of the search array, an attentional template is formed to guide search and reduce the search time. To control this top-down guidance in the target-in-memory condition, we included a target-first condition in which the target identity is presented 50 ms before the search array and remains on screen until response.

The results from Experiment 1 are consistent with the target-reidentification hypothesis. The search slope in the target-in-memory condition was 30.2 ms per item, indicating that the time for identifying a letter was 30.2 ms. The slope doubled in the target-on-screen condition (62.5 ms per item) and the target-first condition (65.5 ms per item), which suggests that, in these two conditions, each letter required a processing time sufficient for identifying two letters. A plausible explanation is that, after checking each distractor, observers reinspected the target. To provide convergent evidence for this possibility, we manipulated the form of the central target in Experiment 2: The central target was either upright or mirror reversed and tilted. Letters in the search array were all upright. We anticipated that it might take observers longer to identify the mirror-reversed and tilted letters than the upright letters. This extra target-encoding time should affect the intercept of the search-time function only if the central target is identified once, but it may increase the search slope if the central target is reinspected after each distractor is examined.

In Experiment 3, there were two types of displays: simple and complex (Fig. 1). In the simple display, the target letter was mirror reversed and tilted, while letters in the search array were upright; in the complex display, the central letter was upright, but letters in the search array were mirror reversed and tilted. In the target-on-screen condition, which display would observers search more quickly? Existing theories predict a faster search in the simple display, but the reidentification hypothesis makes an astonishing prediction, that is, search speeds for the simple and complex displays should be similar. Experiment 3 tested this prediction.

Previous work using eye tracking has suggested that in naturalistic tasks, observers may preferentially refixate parts of the work space rather than committing them to working memory (Ballard, Hayhoe, & Pelz, 1995; Hayhoe, Shrivastava, Mruczek, & Pelz, 2003). Although the search slopes reported here are unlikely to involve eye movements, in Experiment 4, we used a variant of the paradigm in which the target was mostly available in iconic memory and search could be completed with exposure times of less than 200 ms (thus minimizing the risk of eye movements). For this purpose, we switched to numeric digits and used a target preexposure of 30 ms, which was immediately followed either by the search array (immediate condition) or by an annular mask and then (1,000 ms later) by the search array (delayed condition). We reasoned that in the delayed condition, observers would need to consolidate the search target into working memory, but that in the immediate condition, iconic memory might be enough to support reidentification while not causing gaze movements.

The findings of Experiments 1 and 4 showed that when target identity is revealed simultaneously with the search array and remains available for inspection (even in iconic memory), the search slope is twice that as when the target identity is stored in working memory before the search begins. In the no-working-memory (unconsolidated-target) search conditions, observers seemed to jump right into the search, depending on reidentification of the target rather than on first establishing a representation of the search target in working memory. This could explain the drop in search-rate efficiency. In a supplementary study (Experiment S2 in the Supplemental Material), the target-in-memory condition of Experiment 1 was modified so that the previewed target would always reappear at the center of the search array. Search slopes in this hybrid condition remained low, which implies that the observers, rather than being lazy, still preferred a faster search rate, as long as sufficient time was allowed to prepare the target representation (in working memory) to guide attention.

The findings of Experiments 2 and 3 were consistent with the reidentification hypothesis—that is, when target identity is revealed simultaneously with the presentation of the search array and remains available for inspection, observers will reidentify the target after examining each distractor rather than taking the time to first consolidate the target identity into working memory. The present findings cannot be attributed to factors related to eye movements because the reidentification process can occur even in iconic memory and within a duration insufficient for initiating saccadic eye movements. If the reidentification hypothesis is correct, that implies that comparison between the target template and items in the search array does not necessarily occur in working memory and that visual search has an unconsolidatedtarget (working-memory-free) search mode.

Horowitz and Wolfe (1998) showed that search efficiency does not change when the locations of the items in the search array randomly shift every 111 ms compared with when the items’ locations are fixed. They interpreted their findings as showing that the locations of visited items are not remembered (i.e., sampling with replacement; see also Gibson, Li, Skow, Brown, & Cooke, 2000; Gilchrist & Harvey, 2000; Horowitz & Wolfe, 2001, 2003). In fact, the doubled search slope in the nonconsolidated conditions of the present study is reminiscent of findings of this memory-free search. However, such searches have been reported in cases in which target consolidation has clearly occurred and the searched locations are not being consolidated. Some authors have indeed demonstrated conditions in which search occurs without replacement (Kristjánsson, 2000; Lleras, Rensink, & Enns, 2005; Peterson, Kramer, Wang, Irwin, & McCarley, 2001; Takeda, 2004). In the present case, it could be argued that ongoing attempts at consolidating the target interfered with searchlocation consolidation. However, the results of Experiment 3 seem to contradict this account. If searches in the target-on-screen condition did not include target reidentification, it is difficult to understand how search speed in the simple display was not faster than that in the complex display.

Although target reidentification results in a steeper search slope, this strategy eliminates the time normally used for consolidating the target identity, which might involve several hundred milliseconds. Therefore, the overall efficiency of the unconsolidated-target search is likely better than that of the consolidated-target search when there is minimal preview time. Moreover, the benefit of this reidentification strategy is actually consistent with the finding that observers miss changes between two simultaneous arrays, just as they do in a flicker paradigm, but that their performance improves significantly in the simultaneous condition (e.g., ScottBrown, Baker, & Orbach, 2000).

In natural tasks (e.g., making a sandwich), observers may frequently go back to check the model (Ballard et al., 1995; Hayhoe et al., 2003), similar to the target reidentification suggested by the present findings. Although eye movements are clearly involved in those natural tasks, the phenomenon observed in the present study is likely attributable to covert attention, because the findings of Experiment 4 show that the reidentification of the target could occur in iconic memory. It also implies that the comparison between the target template and items in the search array may occur either in iconic memory (Sperling, 1960) or in fragile short-term memory (Sligte, Scholte, & Lamme, 2008, 2009).

翻译考点：
考点1：“the identity of the search target”推荐翻译为“搜索目标本身”
考点2：“iconic memory”应翻译为“映像记忆”
考点3：“preselection, selection, postselection, and decision”推荐翻译为“选择前阶段、选择阶段、选择后阶段和决策阶段”
考点4：“visited distractors”应翻译为“被注意过的干扰项/被检视过的干扰项”，不能翻译为“已访问的干扰项”
考点5：“target-in-memory condition”推荐翻译为“目标在记忆中的条件”
考点6：“target-on-screen condition”推荐翻译为“目标在屏幕上的条件”
考点7：“eye movements”推荐翻译为“眼动”
考点8：“reidentification hypothesis”推荐译为“再识别假设”或“重新识别假设”