Christian N. L. Olivers

Feature-Based Memory-Driven Attentional Capture: Visual Working Memory Content Affects Visual Attention

In 7 experiments, the authors explored whether visual attention (the ability to select relevant visual information) and visual working memory (the ability to retain relevant visual information) share the same content representations. The presence of singleton distractors interfered more strongly with a visual search task when it was accompanied by an additional memory task. Singleton distractors interfered even more when they were identical or related to the object held in memory, but only when it was difficult to verbalize the memory content. Furthermore, this content-specific interaction occurred for features that were relevant to the memory task but not for irrelevant features of the same object or for once-remembered objects that could be forgotten. Finally, memory-related distractors attracted more eye movements but did not result in longer fixations. The results demonstrate memory-driven attentional capture on the basis of content-specific representations.

The beneficial effects of additional task load, positive affect, and instruction on the attentional blink.

The attentional blink reflects the impaired ability to identify the 2nd of 2 targets presented in close succession--a phenomenon that is generally thought to reflect a fundamental cognitive limitation. However, the fundamental nature of this impairment has recently been called into question by the counterintuitive finding that task-irrelevant mental activity improves attentional blink performance (C. N. L. Olivers & S. Nieuwenhuis, 2005). The present study found a reduced attentional blink when participants concurrently performed an additional memory task, viewed pictures of positive affective content, or were instructed to focus less on the task. These findings support the hypothesis that the attentional blink is due to an overinvestment of attentional resources in stimulus processing, a suboptimal processing mode that can be counteracted by manipulations promoting divided attention.

The Beneficial Effect of Concurrent Task-Irrelevant Mental Activity on Temporal Attention

It is believed that the human cognitive system is fundamentally limited in deploying attention over time. This limitation is reflected in the attentional blink, the impaired ability to identify the second of two visual targets presented in close succession. We report the paradoxical finding that the attentional blink is significantly ameliorated when observers are concurrently engaged in distracting mental activity, such as free-associating on a task-irrelevant theme or listening to music. This finding raises questions about the fundamental nature of the attentional blink, and suggests that the temporal dynamics of attention are determined by task circumstances that induce either a more or a less distributed state of mind.

Pip and Pop: Nonspatial Auditory Signals Improve Spatial Visual Search

Searching for an object within a cluttered, continuously changing environment can be a very time-consuming process. The authors show that a simple auditory pip drastically decreases search times for a synchronized visual object that is normally very difficult to find. This effect occurs even though the pip contains no information on the location or identity of the visual object. The experiments also show that the effect is not due to general alerting (because it does not occur with visual cues), nor is it due to top-down cuing of the visual change (because it still occurs when the pip is synchronized with distractors on the majority of trials). Instead, we propose that the temporal information of the auditory signal is integrated with the visual signal, generating a relatively salient emergent feature that automatically draws attention. Phenomenally, the synchronous pip makes the visual object pop out from its complex environment, providing a direct demonstration of spatially nonspecific sounds affecting competition in spatial visual processing.

Audiovisual events capture attention: Evidence from temporal order judgments

Is an irrelevant audiovisual event able to guide attention automatically? In Experiments 1 and 2, participants were asked to make a temporal order judgment (TOJ) about which of two dots (left or right) appeared first. In Experiment 3, participants were asked to make a simultaneity judgment (SJ) instead. Such tasks have been shown to be affected by attention. Lateral to each of the dots, nine irrelevant distractors continuously changed color. Prior to the presentation of the first dot, a spatially non-informative tone was synchronized with the color change of one of these distractors, either on the same side or on the opposite side of the first dot. Even though both the tone and the distractors were completely irrelevant to the task, TOJs were affected by the synchronized distractor. TOJs were not affected when the tone was absent or synchronized with distractors on both sides. SJs were also affected by the synchronized distractor, ruling out an alternative response bias hypothesis. We conclude that audiovisual synchrony guides attention in an exogenous manner.

What drives memory-driven attentional capture? The effects of memory type, display type, and search type.

An important question is whether visual attention (the ability to select relevant visual information) and visual working memory (the ability to retain relevant visual information) share the same content representations. Some past research has indicated that they do: Singleton distractors interfered more strongly with a visual search task when they were identical or related to the object held in memory. However, other research has failed to find such effects despite using very similar procedures. The present study, using the same combined working memory and attentional capture paradigm, demonstrates which factors do (varied mapping, low stimulus energy) and which factors do not (exact type of visual memory method used, difficult nature of search, heterogeneity of displays, and instruction) contribute to this discrepancy.

Interactions between working memory, attention and eye movements

This paper reviews the recent findings on working memory, attention and eye movements. We discuss the research that shows that many phenomena related to visual attention taking place when selecting relevant information from the environment are similar to processes needed to keep information active in working memory. We discuss new data that show that when retrieving information from working memory, people may allocate visual spatial attention to the empty location in space that used to contain the information that has to be retrieved. Moreover, we show that maintaining a location in working memory not only may involve attention rehearsal, but might also recruit the oculomotor system. Recent findings seem to suggest that remembering a location may involve attention-based rehearsal in higher brain areas, while at the same time there is inhibition of specific motor programs at lower brain areas. We discuss the possibility that working memory functions do not reside at a special area in the brain, but emerge from the selective recruitment of brain areas that are typically involved in spatial attention and motor control.

When visual marking meets the attentional blink: More evidence for top-down, limited capacity inhibition

An attentional blink (AB) paradigm was used to investigate the attentional resources necessary for visual marking. The results showed that distractors presented inside the AB cannot easily be ignored despite participants anticipating a future target display. This supports the hypothesis that attentional resources are required for visual marking. In addition, probe dots were better detected on blinked distractors than on successfully ignored distractors, but only when the task required new items to be prioritized. In a final experiment, a stronger negative carry-over effect on search occurred for targets identical to distractors presented outside rather than inside the AB. This suggests that at least part of the inhibitory processes involved in visual marking are nonspatial. The study of visual selective attention focuses on our visual system’s ability to prioritize certain visual events over others. In brief, efficient prioritization depends on the spatial and temporal properties of, as well as the task constraints surrounding, the visual event. In the present study, we considered the interactions between these spatial and temporal factors. Visual selective attention has a strong spatial component. Typically, visual objects relevant to our behavior ( targets) occupy limited spatial regions in a cluttered visual field filled with numerous irrelevant objects (distractors) that are simultaneously present. Sometimes selection of a target is quite effortless. For instance, Treisman and Gelade (1980) found that observers were very efficient in searching for a blue T in a display filled with brown Ts and green Xs. In this single-feature search task it is as if the unique feature (color) of the target guides selection. Typically, therefore, the number of distractors (the display size) has little or no effect on search reaction times (RTs), creating flat slopes for the Display Size RT search functions. In other tasks, selection may be more effortful. For example, Treisman and Gelade found that search for a green T among brown Ts and green Xs was much less efficient than a single-feature search. In this conjunction search, visual attention cannot be guided by the target because the target is defined only by a combination of features it shares with both distractor types. Instead, it is as if attention has to be shifted around the display in an effortful way until the target is found. Typically, therefore, conjunction-search RTs are dependent on the number of items simultaneously present, resulting in a relatively steep search slope (see Wolfe, 1994, and Wolfe, Cave, & Franzel, 1989; for variations; but see Duncan & Humphreys, 1989, for a different explanation).

Visual marking: using time in visual selection

Given human capacity limitations, to behave adaptively we need to prioritise the order of visual processing to ensure that the most relevant information is available to control action. One way to do this is to prioritise processing at a particular location in space. However, there are many situations where this strategy is not possible and recent studies have shown that, in such circumstances, observers can use time as well as space to prioritise selection. We propose that selection by time can be influenced by a process of visual marking, involving an active bias applied in parallel against old items in the field. Here we describe the properties of visual marking in relation to other mechanisms of visual selection.

Remembering a Location Makes the Eyes Curve Away

Working memory is a system that keeps limited information on-line for immediate access by cognitive processes. This type of active maintenance is important for everyday life activities. The present study shows that maintaining a location in spatial working memory affects the trajectories of saccadic eye movements toward visual targets, as the eyes deviate away from the remembered location. This finding provides direct evidence for a strong overlap between spatial working memory and the eye movement system. We argue that curvature is the result of the need to inhibit memory-based eye movement activity in the superior colliculus, in order to allow an accurate saccade to the visual target. Whereas previous research has shown that the eyes may deviate away from visually presented stimuli that need to be ignored, we show that the eyes also curve away from remembered stimuli.