Attentional control adjustments in Eriksen and Stroop task performance can be independent of response conflict

In the Eriksen flanker and colour-word Stroop tasks, the response time (RT) difference between incongruent and congruent trials is smaller following incongruent trials than following congruent trials: the “Gratton effect” (Gratton, Coles, & Donchin, 1992). According to the prevailing conflict-monitoring theory (Botvinick, Braver, Barch, Carter, & Cohen, 2001), the Gratton effect reflects attentional control adjustment following response conflict on incongruent trials. However, because previous studies compared incongruent and congruent trials, it remains unclear to what extent the Gratton effect is driven by incongruent rather than congruent trials. To resolve this issue, we included neutral trials in addition to incongruent and congruent trials in the Eriksen (Experiment 1) and Stroop (Experiment 2) tasks. Participants responded manually and vocally in both tasks. Moreover, we assessed responding to Stroop stimuli that were preceded by neutral cues or by incongruent- or congruent-predicting cues (Experiment 3). In all three experiments, the RT difference between incongruent and congruent trials was larger for postcongruent trials than for postincongruent and postneutral trials. These findings suggest that control adjustments can be independent of response conflict, challenging conflict-monitoring theory.     

Aversive conditioning under conditions of restricted awareness: Effects on spatial cueing

In the literature on aversive conditioning there is still debate on the role of awareness. According to some authors, affective learning can occur with or without contingency learning (dual-process model), whereas others argue that a single process produces both affective responses and contingency knowledge. Although many studies have investigated these models, the results to date are inconclusive. Based on a review of the literature, a new series of experiments was designed to examine aversive conditioning in the absence of contingency awareness. In the present study we examined the effects of subliminal aversive conditioning on a spatial cueing task. Awareness was stringently tested after conditioning. Three kinds of awareness were distinguished: contingency awareness (awareness of the CS?US contingencies, where CS is the conditioned stimulus, and US is the unconditioned stimulus), perceptual awareness (awareness of the perceptual differences between the CSs), and US expectancy (awareness of a threat feeling when confronted with the CS+, but not when confronted with the CS?). The results of three experiments demonstrated that responses on the spatial cueing task were modulated by subliminal aversive conditioning. Importantly, none of the participants was contingency aware or able to perceptually discriminate between the conditioned stimuli. However, in Experiment 3, only those participants showing some level of postconditioning expectancy awareness exhibited conditioning effects. These experiments suggest that subliminal aversive conditioning produces small but significant effects, which may be modulated by expectancy awareness.     

The effect of scene structure on time perception

The current experiments examined the hypothesis that scene structure affects time perception. In three experiments, participants judged the duration of realistic scenes that were presented in a normal or jumbled (i.e., incoherent) format. Experiment 1 demonstrated that the subjective duration of normal scenes was greater than subjective duration of jumbled scenes. In Experiment 2, gridlines were added to both normal and jumbled scenes to control for the number of line terminators, and scene structure had no effect. In Experiment 3, participants performed a secondary task that required paying attention to scene structure, and scene structure's effect on duration judgements reemerged. These findings are consistent with the idea that perceived duration can depend on visual–cognitive processing, which in turn depends on both the nature of the stimulus and the goals of the observer.     

The interruptive effect of pain on attention

Pain is known to disrupt attentional performance in both healthy adults and patients with chronic pain. Exactly which aspects of attentional function are affected are, however, still to be determined. The primary aim of this investigation was to systematically examine the effects of experimentally induced pain on a range of attentional performance tasks. Following a review of tests of attentional disruption, seven best candidate tasks were selected and examined across seven experiments. The tasks were: continuous performance, flanker, endogenous precueing, n-back, inhibition, attentional switching, and divided attention. Healthy adult participants performed each of these tasks under three different conditions: a painful heat sensation, a warm heat sensation, and a nonheat control. Pain differentially affected attentional performance across these tasks; pain-related attentional impairment was found on the n-back, attentional switching, and divided attention tasks, but not on the other tasks. This finding suggests that the aspects of attention most affected by pain are those essential for the completion of complex tasks that require the processing of multiple cues and control over attentional deployment. These results are discussed in the context of an emerging view of pain as a demand for executive control and the development of measures that could be used to examine attentional disruption in the context of pain.     

Orienting numbers in mental space: Horizontal organization trumps vertical

While research on the spatial representation of number has provided substantial evidence for a horizontally oriented mental number line, recent studies suggest vertical organization as well. Directly comparing the relative strength of horizontal and vertical organization, however, we found no evidence of spontaneous vertical orientation (upward or downward), and horizontal trumped vertical when pitted against each other (Experiment 1). Only when numbers were conceptualized as magnitudes (as opposed to nonmagnitude ordinal sequences) did reliable vertical organization emerge, with upward orientation preferred (Experiment 2). Altogether, these findings suggest that horizontal representations predominate, and that vertical representations, when elicited, may be relatively inflexible. Implications for spatial organization beyond number, and its ontogenetic basis, are discussed.     

Attention is required for maintenance of feature binding in visual working memory

Working memory and attention are intimately connected. However, understanding the relationship between the two is challenging. Currently, there is an important controversy about whether objects in working memory are maintained automatically or require resources that are also deployed for visual or auditory attention. Here we investigated the effects of loading attention resources on precision of visual working memory, specifically on correct maintenance of feature-bound objects, using a dual-task paradigm. Participants were presented with a memory array and were asked to remember either direction of motion of random dot kinematograms of different colour, or orientation of coloured bars. During the maintenance period, they performed a secondary visual or auditory task, with varying levels of load. Following a retention period, they adjusted a coloured probe to match either the motion direction or orientation of stimuli with the same colour in the memory array. This allowed us to examine the effects of an attention-demanding task performed during maintenance on precision of recall on the concurrent working memory task. Systematic increase in attention load during maintenance resulted in a significant decrease in overall working memory performance. Changes in overall performance were specifically accompanied by an increase in feature misbinding errors: erroneous reporting of nontarget motion or orientation. Thus in trials where attention resources were taxed, participants were more likely to respond with nontarget values rather than simply making random responses. Our findings suggest that resources used during attention-demanding visual or auditory tasks also contribute to maintaining feature-bound representations in visual working memory—but not necessarily other aspects of working memory.     

The relationship between vertical stimulation and horizontal attentional asymmetries

The original aim was to examine the effect of perceived distance, induced by the Ponzo illusion, on left/right asymmetries for line bisection. In Experiment 1, university students (n?=?29) made left/right bisection judgements for lines presented in the lower or upper half of the screen against backgrounds of the Ponzo stimuli, or a baseline. While the Ponzo illusion had relatively little effect on line bisection, elevation in the baseline condition had a strong effect, whereby the leftward bias was increased for upper lines. Experiment 2 (n?=?17) eliminated the effect of elevation by presenting the line in the middle and moving the Ponzo stimuli relative to the line. Despite this change, the leftward bias was still stronger in the upper condition in the baseline condition. The final experiment (n?=?17) investigated whether upper/lower visual stimulation, which was irrelevant to the task, affected asymmetries for line bisection. The results revealed that a rectangle presented in the upper half of the screen increased the leftward line bisection bias relative to a baseline and lower stimulation condition. These results corroborate neuroimaging research, showing increased right parietal activation associated with shifts of attention into the upper hemispace. This increased right parietal activation may increase the leftward attentional bias—resulting in a stronger leftward bias for line bisection.     

Social event segmentation

Humans are experts in understanding social environments. What perceptual and cognitive processes enable such competent evaluation of social information? Here we show that environmental content is grouped into units of “social perception”, which are formed automatically based on the attentional priority given to social information conveyed by eyes and faces. When asked to segment a clip showing a typical daily scenario, participants were remarkably consistent in identifying the boundaries of social events. Moreover, at those social event boundaries, participants' eye movements were reliably directed to actors' eyes and faces. Participants' indices of attention measured during the initial passive viewing, reflecting natural social behaviour, also showed a remarkable correspondence with overt social segmentation behaviour, reflecting the underlying perceptual organization. Together, these data show that dynamic information is automatically organized into meaningful social events on an ongoing basis, strongly suggesting that the natural comprehension of social content in daily life might fundamentally depend on this underlying grouping process.     

Attention and memory protection: Interactions between retrospective attention cueing and interference

Visual working memory (VWM) and attention have a number of features in common, but despite extensive research it is still unclear how the two interact. Can focused attention improve VWM precision? Can it protect VWM from interference? Here we used a partial-report, continuous-response orientation memory task to examine how attention and interference affect different aspects of VWM and how they interact with one another. Both attention and interference were orthogonally manipulated during the retention interval. Attention was manipulated by presenting informative retro-cues, whereas interference was manipulated by introducing a secondary interfering task. Mixture-model analyses revealed that retro-cues, compared to uninformative cues, improved all aspects of performance: Attention increased recall precision and decreased guessing rate and swap-errors (reporting a wrong item in memory). Similarly, performing a secondary task impaired all aspects of the VWM task. In particular, an interaction between retro-cue and secondary task interference was found primarily for swap-errors. Together these results suggest that both the quantity and quality of VWM representations are sensitive to attention cueing and interference modulations, and they highlight the role of attention in protecting the feature–location associations needed to access the correct items in memory.     

EPS Mid-Career Award 2014

In visual search, observers try to find known target objects among distractors in visual scenes where the location of the targets is uncertain. This review article discusses the attentional processes that are active during search and their neural basis. Four successive phases of visual search are described. During the initial preparatory phase, a representation of the current search goal is activated. Once visual input has arrived, information about the presence of target-matching features is accumulated in parallel across the visual field (guidance). This information is then used to allocate spatial attention to particular objects (selection), before representations of selected objects are activated in visual working memory (recognition). These four phases of attentional control in visual search are characterized both at the cognitive level and at the neural implementation level. It will become clear that search is a continuous process that unfolds in real time. Selective attention in visual search is described as the gradual emergence of spatially specific and temporally sustained biases for representations of task-relevant visual objects in cortical maps.