Christian N L Olivers

• PhD
• Professor (Full) at Vrije Universiteit Amsterdam; VU University Amsterdam

How do we find stuff that we are looking for? This question has been central to many a study in Journal of Experimental Psychology: Human Perception and Performance. We describe how seminal studies in the journal eventually led to the hypothesis that top-down attentional guidance and visual working memory activation might be regarded as one and the...

Previous work has demonstrated that visual working memory of peripherally presented patterns transitions from location-specific to spatially generalized representations. It remains unclear what the temporal dynamics are of this generalization, and to which processing stages it is linked. Here we investigated the neural correlates of peripherally en...

Visual working memory (VWM) retains representations of past visual information for future action. Yet to date, most studies have approached VWM as just serving perception beyond the immediate. Whether and how prospective actions shape information in VWM remains largely unknown, in part because typical experimental setups limit behavior to simple bu...

Working memory is defined as the online storage space for ongoing tasks. It stores both newly encoded information and retrieved long-term memories. However, there is a growing amount of work to suggest that long-term memories can also guide behavior. This raises the question: Why do humans invest metabolic resources in reactivating long-term memori...

While the influence of context on long-term memory (LTM) is well-documented, its effects on the interaction between working memory (WM) and LTM remain less understood. In this study, we explored these interactions using a delayed match-to-sample task, where participants (6 Male, 16 Female) encountered the same target object across six consecutive t...

Findings from recent studies indicate that planning an action toward an object strengthens its visual working memory (VWM) representation, emphasizing the importance of sensorimotor links in VWM. In the present study, we investigated to what extent such sensorimotor links are modulated by how well-defined an action plan is. In three eye-tracking ex...

Flexible updating of information in Visual Working Memory (VWM) is crucial to deal with its limited capacity. Previous research has shown that the removal of no longer relevant information takes some time to complete. Here, we sought to study the time course of such removal by tracking the accompanying drop in load through behavioral and neurophysi...

The efficient utilization of limited working memory (WM) resources involves transferring task-relevant information to long-term memory (LTM) through repetition. While the interaction between context and LTM has been extensively studied, its influence on the dynamics between WM and LTM is less understood. In this study, we explored these dynamics us...

Visual crowding is arguably the strongest limitation imposed on extrafoveal vision, and is a relatively well-understood phenomenon. However, most investigations and theories are based on sparse displays consisting of a target and at most a handful of flanker objects. Recent findings suggest that the laws thought to govern crowding may not hold for...

Where we move our eyes during visual search is controlled by the relative saliency and relevance of stimuli in the visual field. However, the visual field is not homogeneous, as both sensory representations and attention change with eccentricity. Here we present an experiment investigating how eccentricity differences between competing stimuli affe...

Flexible updating of information in Visual Working Memory (VWM) is crucial to deal with its limited capacity. Previous research has shown that the removal of no longer relevant information takes some time to complete. Here, we sought to study the time course of such removal by tracking the accompanying drop in load through behavioral and neurophysi...

Visual working memory is believed to rely on top-down attentional mechanisms that sustain active sensory representations in early visual cortex. However, both bottom-up sensory input and top-down attentional modulations thereof have been shown to be biased towards the fovea, at the expense of the periphery, and initially peripheral percepts may eve...

Visual attention may be captured by an irrelevant yet salient distractor, thereby slowing search for a relevant target. This phenomenon has been widely studied using the additional singleton paradigm in which search items are typically all presented at one and the same eccentricity. Yet, differences in eccentricity may well bias the competition bet...

An important function of peripheral vision is to provide the target of the next eye movement. Here we investigate the extent to which the eyes are biased to select a target closer to fixation over one further away. Participants were presented with displays containing two identical singleton targets and were asked to move their eyes to either one of...

Our visual environment is relatively stable over time. An optimized visual system could capitalize on this by devoting less representational resources to objects that are physically present. The vividness of subjective experience, however, suggests that externally available (perceived) information is more strongly represented in neural signals than...

Attention has frequently been regarded as an emergent property of linking sensory representations to action plans. It has recently been proposed that similar mechanisms may operate within visual working memory (VWM), such that linking an object in VWM to an action plan strengthens its sensory memory representation, which then expresses as an attent...

Visual working memory has been proven to be relatively robust against interference. However, little is known on whether such robust coding is obligatory, or can be flexibly recruited depending on its expected usefulness. To address this, participants remembered both the color and orientation of a grating. During the maintenance, we inserted a secon...

Human vision involves selectively directing the eyes to potential objects of interest. According to most prominent theories, selection is the quantal outcome of an ongoing competition between saliency-driven signals on the one hand, and relevance-driven signals on the other, with both types of signals continuously and concurrently projecting onto a...

Working memory is essential: it serves to guide intelligent behavior of humans and nonhuman primates when task-relevant stimuli are no longer present to the senses. Moreover, complex tasks often require that multiple working memory representations can be flexibly and independently maintained, prioritized, and updated according to changing task dema...

Human time perception is malleable and subject to many biases. For example, it has repeatedly been shown that stimuli that are physically intense or that are unexpected seem to last longer. Two competing hypotheses have been proposed to account for such biases: One states that these temporal illusions are the result of increased levels of arousal t...

Different theories have been proposed to explain how the human brain derives an accurate sense of time. One specific class of theories, intrinsic clock theories, postulate that temporal information of a stimulus is represented much like other features such as color and location, bound together to form a coherent percept. Here, we explored to what e...

Visual search is an integral part of human behavior and has proven important to understanding mechanisms of perception, attention, memory, and oculomotor control. Thus far, the dominant theoretical framework posits that search is mainly limited by covert attentional mechanisms, comprising a central bottleneck in visual processing. A different class...

Both saliency and goal information are important factors in driving visual selection. Saliency-driven selection occurs primarily in early responses, whereas goal-driven selection happens predominantly in later responses. Here, we investigated how eccentricity affects the time courses of saliency-driven and goal-driven visual selection. In three exp...

Background Traditionally, EEG/MEG data are high-pass filtered and baseline-corrected to remove slow drifts. Minor deleterious effects of high-pass filtering in traditional time-series analysis have been well-documented, including temporal displacements. However, its effects on time-resolved multivariate pattern classification analyses (MVPA) are la...

To optimize task sequences, the brain must differentiate between current and prospective goals. We previously showed that currently and prospectively relevant object representations in working memory can be dissociated within object-selective cortex. Based on other recent studies indicating that a range of brain areas may be involved in distinguish...

Visual search and working memory (WM) are tightly linked cognitive processes. Theories of attentional selection assume that WM plays an important role in top-down guided visual search. However, computational models of visual search do not model WM. Here we show that an existing model of WM can utilize its mechanisms of rapid plasticity and pattern...

Different models have been proposed to explain how the human brain derives an accurate sense of time. One specific class of models, intrinsic models, state that temporal information of a stimulus is represented much like other features such as color and location, bound together to form a coherent percept. Here we explored to what extent this holds...

From the conception of Baddeley’s visuospatial sketchpad, visual working memory and visual attention have been closely linked concepts. An attractive model has advocated unity of the two cognitive functions, with attention serving the active maintenance of sensory representations. However, empirical evidence from various paradigms and dependent mea...

Human time perception is malleable and subject to many biases. For example, it has repeatedly been shown that stimuli that are physically intense or that are unexpected seem to last longer. Two competing hypotheses have been proposed to account for such biases: one states that these temporal illusions are the result of increased levels of arousal w...

Can individuals look for multiple objects at the same time? A simple question, but answering it has proven difficult. In this review, we describe possible cognitive architectures and their predictions about the capacity of visual search. We broadly distinguish three stages at which limitations may occur: (1) preparation (establishing and maintainin...

Evidence shows that observers preactivate a target representation in preparation of a visual selection task. In this study, we addressed the question if and how preparing to ignore an anticipated distractor differs from preparing for an anticipated target. We measured EEG while participants memorized a laterally presented color, which was cued to b...

Working memory is essential for intelligent behavior as it serves to guide behavior of humans and nonhuman primates when task-relevant stimuli are no longer present to the senses. Moreover, complex tasks often require that multiple working memory representations can be flexibly and independently maintained, prioritized, and updated according to cha...

In the visual world, attention is guided by perceptual goals activated in visual working memory (VWM). However, planning multiple-task sequences also requires VWM to store representations for future goals. These future goals need to be prevented from interfering with the current perceptual task. Recent findings have implicated neural oscillations a...

Selective attention plays a prominent role in prioritizing information in working memory (WM), improving performance for attended representations. However, it remains unclear whether unattended WM representations suffer from information loss. Here we tested the hypothesis that within WM, selectively attending to an item and stopping storing other i...

There are conflicting views on whether the storage of visual working memory (VWM) involves active maintenance mechanism. If so, it should suffer from secondary tasks that tap into the same mechanisms during the delay. We found that when observers were asked to remember a visual pattern, the interference from a secondary task was only momentary. Thi...

The human brain recurrently prioritizes task-relevant over task-irrelevant visual information. A central, question is whether multiple objects can be prioritized simultaneously. To answer this, we let observers search for two colored targets among distractors. Crucially, we independently varied the number of target colors that observers anticipated...

In the research literature, attention and working memory are often intimately linked. In his excellent target article, Oberauer concludes that attention is not a necessary requirement for working memory maintenance. In our reply, we argue that attention is an emergent property of maintaining the current task goal. Humans can flexibly transfer the s...

Cognitive control can involve proactive (preparatory) and reactive (corrective) mechanisms. Using a gaze-contingent eye tracking paradigm combined with fMRI, we investigated the involvement of these different modes of control and their underlying neural networks, when switching between different targets in multiple-target search. Participants simul...

Visual attention serves to select relevant visual information. However, observers often first need to find out what is relevant. Little is known about this information-seeking process and how it affects attention. We employed a cued visual search task in combination with eye tracking to investigate which oculomotor measures reflect the acquisition...

We are constantly extracting regularities from the visual environment to optimize attentional orienting. Here we examine the phenomenon that recurrent presentation of distractors in a specific location leads to its attentional suppression. Specifically, we address the question whether suppression is specific to the spatial regularities of distracto...

Human observers have the remarkable ability to efficiently prioritize task-relevant over task-irrelevant visual information. Yet, a fundamental question remains whether this ability is limited to a single task relevant item, or whether multiple items can be prioritized simultaneously. The answer to this question depends on 1) whether observers can...

There is ongoing debate on whether object meaning can be processed outside foveal vision, making semantics available for attentional guidance. Much of the debate has centred on whether objects that do not fit within an overall scene draw attention, in complex displays that are often difficult to control. Here, we revisited the question by reanalysi...

We are constantly extracting regularities from the visual environment to optimize attentional orienting. Here we examine the phenomenon that recurrent presentation of distractors in a specific location leads to its attentional suppression. Specifically, we address the question whether suppression is specific to the spatial regularities of distracto...

Maintaining information in visual working memory (VWM) biases attentional selection of concurrent visual input, by favoring VWM-matching over VWM-mismatching visual input. Recently, it was shown that this bias disappears when the same item is memorized on consecutive occasions (as memoranda presumably transit from VWM to long-term memory), but reem...

Information in visual working memory that is only prospectively relevant can nevertheless guide attention towards memory matching visual input. Previous studies demonstrated that such memory-based attentional biases can be modulated by top-down processing strategies. Here we examined whether attentional capture by memory matching distractors is als...

Daily life is filled with sequences of multiple tasks, each with their own relevant perceptual input. Working memory needs to dissociate representations that drive attention towards currently relevant information from prospective representations that are needed for future tasks, but that until then should be prevented from guiding attention. Yet, l...

Cognitive control can involve proactive (preparatory) and reactive (corrective) mechanisms. Using a gaze-contingent eye tracking paradigm combined with fMRI, we investigated the involvement of these different modes of control and their underlying neural networks, when switching between different targets in multiple-target search. Participants simul...

Background Traditionally, EEG/MEG data are high-pass filtered and baseline-corrected to remove slow drifts. Minor deleterious effects of high-pass filtering in traditional time-series analysis have been well-documented, including temporal displacements. However, its effects on time-resolved multivariate pattern classification analyses (MVPA) are la...

We are constantly extracting regularities from the visual environment to optimize attentional orienting. Here we examine the phenomenon that recurrent presentation of distractors in a specific location leads to its attentional suppression. Specifically, we address the question whether suppression is specific to the spatial regularities of distracto...

Many important situations require human observers to simultaneously search for more than one object. Despite a long history of research into visual search, the behavioral and neural mechanisms associated with multiple-target search are poorly understood. Here we test the novel theory that the efficiency of looking for multiple targets critically de...

We report two psychophysical experiments that investigate a visual illusion that is considered common knowledge among type designers, but has never been studied scientifically. Specifically, the thickness of a horizontal line is overestimated in relation to that of a vertical line. Experiment 1 confirmed the existence of the illusion. In Experiment...

Adaptive behavior requires the separation of current from future goals in working memory. We used fMRI of object-selective cortex to determine the representational (dis)similarities of memory representations serving current and prospective perceptual tasks. Participants remembered an object drawn from three possible categories as the target for one...

Supplementary data to: de Vries, I.E.J., van Driel, J., Karacaoglu, M., Olivers, C.N.L., 2018. Priority Switches in Visual Working Memory are Supported by Frontal Delta and Posterior Alpha Interactions. Cereb. Cortex 28, 4090–4104. https://doi.org/10.1093/cercor/bhy223

Many important situations require human observers to simultaneously search for more than one object. Despite a long history of research into visual search, the behavioral and neural mechanisms associated with multiple-target search are poorly understood. Here we test the novel theory that the efficiency of looking for multiple targets critically de...

Visual working memory (VWM) distinguishes between representations relevant for imminent versus future perceptual goals. We investigated how the brain sequentially prioritizes visual working memory representations that serve consecutive tasks. Observers remembered two targets for a sequence of two visual search tasks, thus making one target currentl...

Having to look for multiple targets typically results in switch costs. However, using a gaze-contingent eyetracking paradigm with multiple color-defined targets, we have recently shown that the emergence of switch costs depends on whether observers can choose a target or a target is being imposed upon them. Here, using a similar paradigm, we tested...

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

In recent years, time-resolved multivariate pattern analysis (MVPA) has gained much popularity in the analysis of electroencephalography (EEG) and magnetoencephalography (MEG) data. However, MVPA may appear daunting to those who have been applying traditional analyses using event-related potentials (ERPs) or event-related fields (ERFs). To ease thi...

Adaptive behavior requires the separation of current from future behavioural goals in working memory. We used fMRI of object-selective cortex to determine the representational (dis)similarities of memory representations serving current and prospective perceptual tasks. Human participants remembered different target objects for two consecutive visua...

Selective attention plays a prominent role in prioritizing information in working memory (WM), improving performance for attended representations. However, it remains unclear what the consequences of selection are for the maintenance of unattended WM representations, and whether this results in information loss. Here we tested the hypothesis that w...

Current theories assume a functional role for covert attention in the maintenance of spatial information in working memory. Consistent with this view, both the locus of attention and positions stored in working memory can be decoded based on the topography of oscillatory alpha-band (8–12 Hz) activity on the scalp. Thus far, however, alpha modulatio...

When observers search for a specific target, it is assumed that they activate a representation of the task relevant object in visual working memory (VWM). This representation – often referred to as the template – guides attention towards matching visual input. In two experiments we tested whether the pupil response can be used to differentiate stim...

Evidence shows that visual working memory (VWM) is strongly served by attentional mechanisms, whereas other evidence shows that VWM representations readily survive when attention is being taken away. To reconcile these findings, we tested the hypothesis that directing attention away makes a memory representation vulnerable to interference from the...

Visual working memory (VWM) representations can be strengthened by pre-cues presented before, and retro-cues presented after, the memory display, providing evidence that attentional orienting plays a role in memory encoding and maintenance. It is unknown whether attentional orienting to VWM stimuli can also have adverse effects (known as inhibition...

Working memory is the function by which we temporarily maintain information to achieve current task goals. Models of working memory typically debate where this information is stored, rather than how it is stored. Here we ask instead what neural mechanisms are involved in storage, and how these mechanisms change as a function of task goals. Particip...

A “target template”, specifying target features, is thought to benefit visual search performance. Setting up a “negative template”, specifying distractor features, should improve distractor inhibition and also benefit target detection. In the current fMRI study, subjects were required to search for a target among distractors enclosed in coloured ci...

Visual search is thought to be guided by an active visual working memory (VWM) representation of the taskrelevant features, referred to as the search template. In three experiments using a probe technique, we investigated which eye movement metrics reveal which search template is activated prior to the search, and distinguish it from future relevan...

It is debated whether people can actively search for more than one object or whether this results in switch costs. Using a gaze-contingent eye-tracking paradigm, we revealed a crucial role for cognitive control in multiple-target search. We instructed participants to simultaneously search for two target objects presented among distractors. In one c...

Visual attention is biased by both visual and semantic representations activated by words. We investigated to what extent language-induced visual and semantic biases are subject to task demands. Participants memorized a spoken word for a verbal recognition task, and performed a visual search task during the retention period. Crucially, while the wo...

The primary electrophysiological marker of feature-based selection is the N2pc, a lateralized posterior negativity emerging around 180–200 ms. As it relies on hemispheric differences, its ability to discriminate the locus of focal attention is severely limited. Here we demonstrate that multivariate analyses of raw EEG data provide a much more fine-...

Models of biased competition assume that pre-activating a visual representation in visual working memory (VWM) biases perception towards memory-matching objects. Consistent with this, it has been shown that targets suppressed by interocular competition gain prioritized access to awareness when they match VWM content. Thus far, these VWM biases duri...

The primary electrophysiological marker of feature-based selection is the N2pc, a lateralized posterior negativity emerging around 180-200 ms. As it relies on hemispheric differences, its ability to discriminate the locus of focal attention is severely limited. Here we demonstrate that multivariate analyses of raw EEG data provide a much more fine-...

Significance Our brain constantly selects salient and/or goal-relevant objects from the visual environment, so that it can operate on neural representations of these objects, but what is the fate of objects that are not selected? Are these discarded so that the brain only has an impoverished nonperceptual representation of them, or does the brain c...