Establishing the separable contributions of spatial attention and saccade preparation across tasks with varying acuity demands.

One common way to investigate the relationship between eye movements and attention is to pair the cueing paradigm with a saccadic dual-task. Here eye movements are directed to one location in the visual field, while a spatial cue simultaneously directs attention to the same or a different location. The magnitude of the cueing effect is then compared between trials where gaze is maintained at fixation and trials where eye movements are prepared. As these comparisons typically occur across blocked single and dual-task conditions, it is difficult to address possible confounds due to changes in response caution. In this paper we use evidence accumulation modeling to remove this confound and extract a measure of orienting that can be used to quantify and compare the influence of spatial attention across four different manipulations of eye movements: 2 that require fixation and 2 that require saccade preparation. The results demonstrate that the magnitude of the cueing effect is similar regardless of eye movement condition or perceptual task. The perceptual benefit associated with preparing a saccade, in contrast, was found to vary by perceptual task. Taken together these results establish that spatial attention and saccade preparation are separable and, we suggest, mediated by distinct underlying mechanisms. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Using evidence accumulation modeling to quantify the relative contributions of spatial attention and saccade preparation in perceptual tasks.

A typical way to investigate the relationship between spatial attention and the programming of an eye movement is with a dual-task. Here, participants simultaneously make an eye movement in 1 direction and discriminate a target at the same or a different location. Results of these tasks consistently find that performance is best at the goal of an upcoming eye movement. It is less clear, however, the extent to which spatial attention can shift independently of the programmed saccade. In this article, for the first time, we use an evidence accumulation model to examine this longstanding question. Specifically, across 2 studies, we quantify the relative contributions of spatial attention and saccade preparation in a perceptual dual-task. Our results establish that there is a unique and measurable effect of spatial attention away from the saccade goal, and, interestingly, that the relative magnitude of this effect varies by cue type. There is a larger influence of spatial attention when a peripheral rather than a central cue is employed. We suggest that these results support the claim that each form of orienting is mediated by a distinct underlying mechanism. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Spatial Attention and Saccade Preparation Both Independently Contribute to the Discrimination of Oblique Orientations.

The extent to which the preparation of an eye movement and spatial attention both independently influence performance within the same task has long been debated. In a recent study that combined computational modelling with a dual-task, both saccade preparation and spatial cueing were revealed to separately contribute to the discrimination of targets oriented along the cardinal axis (horizontal and vertical). However, it remains to be seen whether and to what degree the same holds true when different perceptual stimuli are used. In the present study, we combined evidence accumulation modelling with a dual-task paradigm to assess the extent to which both saccade preparation and spatial attention contribute to the discrimination of full contrast targets oriented along the oblique axis (diagonal). The results revealed a separate and quantifiable contribution of both types of orienting to discrimination performance. Comparison of the magnitude of these effects to those obtained for cardinal orientation discrimination revealed the influence of saccade preparation and spatial attention to be six times smaller for oblique orientations. Importantly, the results revealed a separate and quantifiable contribution of both saccade preparation and spatial attention regardless of perceptual stimuli or stimulus contrast.

A reach-to-touch investigation on the nature of reading in the Stroop task.

In a Stroop task, participants can be presented with a color name printed in color and need to classify the print color while ignoring the word. The Stroop effect is typically calculated as the difference in mean response time (RT) between congruent (e.g., the word RED printed in red) and incongruent (GREEN in red) trials. Delta plots compare not just mean performance, but the entire RT distributions of congruent and incongruent conditions. However, both mean RT and delta plots have some limitations. Arm-reaching trajectories allow a more continuous measure for assessing the time course of the Stroop effect. We compared arm movements to congruent and incongruent stimuli in a standard Stroop task and a control task that encourages processing of each and every word. The Stroop effect emerged over time in the control task, but not in the standard Stroop, suggesting words may be processed differently in the two tasks.

Distinguishing the time- and magnitude-difference accounts of the Simon effect: Evidence from the reach-to-touch paradigm.

A Simon effect occurs when the irrelevant spatial attributes of a stimulus conflict with choice responses based on non-spatial stimulus attributes. Many theories of the Simon effect assume that activation from task-irrelevant spatial attributes becomes available before the activation from task-relevant attributes. We refer to this as the time-difference account. Other theories follow a magnitude-difference account, assuming activation from relevant and irrelevant attributes becomes available at the same time, but with the activation from irrelevant attributes initially being stronger. To distinguish these two accounts, we incorporated the response-signal procedure into the reach-to-touch paradigm to map out the emergence of the Simon effect. We also used a carefully calibrated neutral condition to reveal differences in the initial onset of the influence of relevant and irrelevant information. Our results establish that irrelevant spatial information becomes available earlier than relevant non-spatial information. This finding is consistent with the time-difference account and inconsistent with the magnitude-difference account. However, we did find a magnitude effect, in the form of reduced interference from irrelevant information, for the second of a sequence of two incongruent trials.

The upper-hemifield advantage for masked face processing: Not just an attentional bias.

Recent evidence suggests that face processing may be more robust in the upper visual field (UVF) than in the lower visual field (LVF). We asked whether this UVF advantage is due to an upward bias in participants' visuospatial attention. Participants classified the sex of a UVF or LVF target face that was preceded by a congruent or incongruent masked prime face. We manipulated spatial attention within subjects by varying the predictability of target location across sessions (UVF:LVF ratio of 50:50 on Day 1 and 20:80 on Day 2). When target location was unpredictable, priming emerged earlier in the UVF (~165 ms) than the LVF (~195 ms). This UVF advantage was reversed when targets were more likely to be presented in the LVF. Here priming arose earlier for LVF targets (~53 ms) than UVF targets (~165 ms). Critically, however, UVF primes were processed to the same degree regardless of whether spatial attention was diffuse (Day 1) or deployed elsewhere (Day 2). We conclude that, while voluntarily directed spatial attention is sufficient to modulate the processing of masked faces in the LVF, it is not sufficient to explain the UVF advantage for masked face processing.

Direct evidence of cognitive control without perceptual awareness.

A central question within the domain of human cognition is whether or not the ability to replace a current action with a new one (i.e., cognitive control) depends on a conscious appreciation of the environmental change that necessitates the new behavior. Specifically, it is not yet known if non-consciously perceived stimuli can trigger the modification of a currently ongoing action. We show for the first time that individuals are able to use non-consciously perceived information to modify the course and outcome of an ongoing action. Participants were presented with a masked (i.e., subliminal) 'stop' or 'go-on' prime stimulus whilst performing a routine reach-to-touch action. Despite being invisible to participants, the stop primes produced more hesitations mid-flight and more movement reversals than the go-on primes. This new evidence directly establishes that cognitive control (i.e., the ability to modify a currently ongoing action) does not depend on a conscious appreciation of the environmental trigger.

Face-sex categorization is better above fixation than below: Evidence from the reach-to-touch paradigm.

The masked congruence effect (MCE) elicited by nonconsciously presented faces in a sex-categorization task has recently been shown to be sensitive to the effects of attention. Here we investigated how spatial location along the vertical meridian modulates the MCE for face-sex categorization. Participants made left and right reaching movements to classify the sex of a target face that appeared either immediately above or below central fixation. The target was preceded by a masked prime face that was either congruent (i.e., same sex) or incongruent (i.e., opposite sex) with the target. In the reach-to-touch paradigm, participants typically classify targets more efficiently (i.e., their finger heads in the correct direction earlier and faster) on congruent than on incongruent trials. We observed an upper-hemifield advantage in the time course of this MCE, such that primes affected target classification sooner when they were presented in the upper visual field (UVF) rather than the lower visual field (LVF). Moreover, we observed a differential benefit of attention between the vertical hemifields, in that the MCE was dependent on the appropriate allocation of spatial attention in the LVF, but not the UVF. Taken together, these behavioral findings suggest that the processing of faces qua faces (e.g., sex-categorization) is more robust in upper-hemifield locations.

Dismissing subliminal perception because of its famous problems is classic "baby with the bathwater".

Newell & Shanks (N&S) appeal to well-known problems in establishing subliminality to argue that there is little convincing evidence that subliminally presented stimuli can affect decision making. We discuss how recent studies have successfully addressed these well-known problems and, in turn, have revealed clear evidence that subliminally presented stimuli can affect decision making.

Pointing the way to new constraints on the dynamical claims of computational models.

The reach-to-touch paradigm has become an increasingly popular tool in the study of human cognition. It is widely held that reaching responses are able to reveal the moment-by-moment unfolding of decision processes by virtue of an assumed continuity between reaching trajectories and the underlying "cognitive trajectory." Yet the standard analysis of reaching trajectories aggregates the trajectories across stimulus viewing times, which yields ambiguous results. Here we introduce a new version of the reach-to-touch paradigm that incorporates the response-signal procedure to elicit reaching movements across a wide range of stimulus viewing times. We then analyze the direction of the initial movement by stimulus viewing time, which produces a sigmoidal growth pattern. Of note, we show how this sigmoidal relationship between stimulus viewing time and initial direction can be used to test and constrain the dynamical claims of computational models of basic cognitive processes. We introduce our new version of the reach-to-touch paradigm and analyses in the context of a lexical decision task and we compare our results with the dynamical claims of the dual-route cascaded model of reading.

Responding to the direction of the eyes: in search of the masked gaze-cueing effect.

Recent studies have demonstrated that masked gaze cues can produce a cueing effect. Those studies, however, all utilized a localization task and, hence, are ambiguous with respect to whether the previously observed masked gaze-cueing effect reflects the orienting of attention or the preparation of a motor response. The aim of the present study was to investigate this issue by determining whether masked gaze cues can modulate responses in detection and discrimination tasks, both of which isolate spatial attention from response priming. First, we found a gaze-cueing effect for unmasked cues in detection, discrimination, and localization tasks, which suggests that the gaze-cueing effect for visible cues is not task dependent. Second, and in contrast, we found a gaze-cueing effect for masked cues in a localization task, but not in detection or discrimination tasks, which suggests that the gaze-cueing effect for masked cues is task dependent. Therefore, the present study shows that the masked gaze-cueing effect is attributed to response priming, as opposed to the orienting of spatial attention.

Gaining the upper hand: evidence of vertical asymmetry in sex-categorisation of human hands.

Visual perception is characterised by asymmetries arising from the brain's preferential response to particular stimulus types at different retinal locations. Where the lower visual field (LVF) holds an advantage over the upper visual field (UVF) for many tasks (e.g., hue discrimination, contrast sensitivity, motion processing), face-perception appears best supported at above-fixation locations (Quek & Finkbeiner, 2014a). This finding is consistent with Previc's (1990) suggestion that vision in the UVF has become specialised for object recognition processes often required in "extrapersonal" space. Outside of faces, however, there have been very few investigations of vertical asymmetry effects for higher-level objects. Our aim in the present study was, thus, to determine whether the UVF advantage reported for face-perception would extend to a nonface object - human hands. Participants classified the sex of hand images presented above or below central fixation by reaching out to touch a left or right response panel. On each trial, a briefly presented spatial cue captured the participant's spatial attention to either the location where the hand was about to appear (valid cue) or the opposite location (invalid cue). We observed that cue validity only modulated the efficiency of the sex-categorisation response for targets in the LVLVF and not the UVF, just as we have reported previously for face-sex categorisation (Quek & Finkbeiner, 2014a). Taken together, the data from these studies provide some empirical support for Previc's (1990) speculation that object recognition processes may enjoy an advantage in the upper-hemifield.

The negative compatibility effect with relevant masks: a case for automatic motor inhibition.

For many years controversy has surrounded the so-called "negative compatibility effect" (NCE), a surprising phenomenon whereby responses to a target stimulus are delayed when the target is preceded by an unconscious, response-compatible prime. According to proponents of the "self-inhibition" hypothesis, the NCE occurs when a low-level self-inhibitory mechanism supresses early motor activations that are no longer supported by perceptual evidence. This account has been debated, however, by those who regard the NCE to be a stimulus-specific phenomenon that can be explained without recourse to a self-inhibitory mechanism. The present study used a novel reach-to-touch paradigm to test whether unconscious response priming would manifest as motor activation of the opposite-to-prime response (supporting mask-induced priming accounts), or motor inhibition of the primed response (supporting the notion of low-level self-inhibition). This paper presents new findings that show the emergence of positive and negative compatibility effects as they occur in stimulus processing time. In addition, evidence is provided suggesting that the NCE is not driven by the activation of the incorrect, "opposite-to-prime" response, but rather might reflect automatic motor inhibition.

Masked and unmasked priming in schizophrenia.

Dehaene et al. (2003) showed an absence of conscious, but not masked, conflict effects when patients with schizophrenia performed a number-categorisation priming task. We aimed to replicate these influential results using a different word-categorisation priming task. Counter to Dehaene et al.'s findings, 21 patients and 20 healthy controls showed similar congruence effects for both masked and visible primes. Within patients, a reduced congruence effect for visible primes associated with longer duration of illness and more severe behavioural disorganisation. Patients, unlike controls, were no slower to respond to targets that followed visible compared to masked primes. Conscious conflict effects on priming tasks are not universally reduced in schizophrenia but may associate with chronicity and behavioural disorganisation. That patients were no slower when the preceding primes were clearly visible accords with evidence elsewhere that information processing in schizophrenia is driven more by immediate conscious experience and constrained less by prior events.

Spatial and temporal attention modulate the early stages of face processing: behavioural evidence from a reaching paradigm.

A presently unresolved question within the face perception literature is whether attending to the location of a face modulates face processing (i.e. spatial attention). Opinions on this matter diverge along methodological lines - where neuroimaging studies have observed that the allocation of spatial attention serves to enhance the neural response to a face, findings from behavioural paradigms suggest face processing is carried out independently of spatial attention. In the present study, we reconcile this divide by using a continuous behavioural response measure that indexes face processing at a temporal resolution not available in discrete behavioural measures (e.g. button press). Using reaching trajectories as our response measure, we observed that although participants were able to process faces both when attended and unattended (as others have found), face processing was not impervious to attentional modulation. Attending to the face conferred clear benefits on sex-classification processes at less than 350ms of stimulus processing time. These findings constitute the first reliable demonstration of the modulatory effects of both spatial and temporal attention on face processing within a behavioural paradigm.

Subcortical human face processing? Evidence from masked priming.

Face processing without awareness might depend on subcortical structures (retino-collicular projection), cortical structures, or a combination of the two. The present study was designed to tease apart these possibilities. Because the retino-collicular projection is more sensitive to low spatial frequencies, we used masked (subliminal) face prime images that were spatially low-pass filtered, or high-pass filtered. The masked primes were presented in the periphery prior to clearly visible target faces. Participants had to discriminate between male and female target faces and we recorded prime-target congruence effects--that is, the difference in discrimination speed between congruent pairs (with prime and target of the same sex) and incongruent pairs (with prime and target of different sexes). In two experiments, we consistently find that masked low-pass filtered face primes produce a congruence effect and that masked high-pass filtered face primes do not. Together our results support the assumption that the retino-collicular route which carries the low spatial frequencies also conveys sex specific features of face images contributing to subliminal face processing.

Effective processing of masked eye gaze requires volitional control.

The purpose of the present study was to establish whether the validity effect produced by masked eye gaze cues should be attributed to strictly reflexive mechanisms or to volitional top-down mechanisms. While we find that masked eye gaze cues are effective in producing a validity effect in a central cueing paradigm, we also find that the efficacy of masked gaze cues is sharply constrained by the experimental context. Specifically, masked gaze cues only produced a validity effect when they appeared in the context of unmasked and predictive gaze cues. Unmasked gaze cues, in contrast, produced reliable validity effects across a range of experimental contexts, including Experiment 4 where 80% of the cues were invalid (counter-predictive). Taken together, these results suggest that the effective processing of masked gaze cues requires volitional control, whereas the processing of unmasked (clearly visible) gaze cues appears to benefit from both reflexive and top-down mechanisms.

Subliminal priming with nearly perfect performance in the prime-classification task.

The subliminal priming paradigm is widely used by cognitive scientists, and claims of subliminal perception are common nowadays. Nevertheless, there are still those who remain skeptical. In a recent critique of subliminal priming, Pratte and Rouder (Attention, Perception, & Psychophysics, 71, 1276-1283, 2009) suggested that previous claims of subliminal priming may have been due to a failure to control the task difficulty between the experiment proper and the prime-classification task. Essentially, because the prime-classification task is more difficult than the experiment proper, the prime-classification task results may underrepresent the subjects' true ability to perceive the prime stimuli. To address this possibility, prime words were here presented in color. In the experiment proper, priming was observed. In the prime-classification task, subjects reported the color of the primes very accurately, indicating almost perfect control of task difficulty, but they could not identify the primes. Thus, I conclude that controlling for task difficulty does not eliminate subliminal priming.

Viewing and feeling touch modulates hand position for reaching.

Action requires knowledge of our body location in space. Here we asked if interactions with the external world prior to a reaching action influence how visual location information is used. We investigated if the temporal synchrony between viewing and feeling touch modulates the integration of visual and proprioceptive body location information for action. We manipulated the synchrony between viewing and feeling touch in the Rubber Hand Illusion paradigm prior to participants performing a ballistic reaching task to a visually specified target. When synchronous touch was given, reaching trajectories were significantly shifted compared to asynchronous touch. The direction of this shift suggests that touch influences the encoding of hand position for action. On the basis of this data and previous findings, we propose that the brain uses correlated cues from passive touch and vision to update its own position for action and experience of self-location.

The flexibility of nonconsciously deployed cognitive processes: evidence from masked congruence priming.

BACKGROUND: It is well accepted in the subliminal priming literature that task-level properties modulate nonconscious processes. For example, in tasks with a limited number of targets, subliminal priming effects are limited to primes that are physically similar to the targets. In contrast, when a large number of targets are used, subliminal priming effects are observed for primes that share a semantic (but not necessarily physical) relationship with the target. Findings such as these have led researchers to conclude that task-level properties can direct nonconscious processes to be deployed exclusively over central (semantic) or peripheral (physically specified) representations. PRINCIPAL FINDINGS: We find distinct patterns of masked priming for "novel" and "repeated" primes within a single task context. Novel primes never appear as targets and thus are not seen consciously in the experiment. Repeated primes do appear as targets, thereby lending themselves to the establishment of peripheral stimulus-response mappings. If the source of the masked priming effect were exclusively central or peripheral, then both novel and repeated primes should yield similar patterns of priming. In contrast, we find that both novel and repeated primes produce robust, yet distinct, patterns of priming. CONCLUSIONS: Our findings indicate that nonconsciously elicited cognitive processes can be flexibly deployed over both central and peripheral representations within a single task context. While we agree that task-level properties can influence nonconscious processes, our findings sharply constrain the extent of this influence. Specifically, our findings are inconsistent with extant accounts which hold that the influence of task-level properties is strong enough to restrict the deployment of nonconsciously elicited cognitive processes to a single type of representation (i.e. central or peripheral).