What happens during the stimulus onset asynchrony in the dot-probe task? Exploring the role of eye movements in the assessment of attentional biases

Attentional bias towards happy faces in the dot-probe paradigm: it depends on which task is used

Two recent articles [Gronchi et al., 2018. Automatic and controlled attentional orienting in the elderly: A dual-process view of the positivity effect. Acta Psychologica, 185, 229-234; Wirth & Wentura, 2020. It occurs after all: Attentional bias towards happy faces in the dot-probe task. Attention, Perception, & Psychophysics, 82(5), 2463-2481] report attentional biases for happy facial expressions in the dot-probe paradigm, albeit in different directions. While Wirth and Wentura report a bias towards happy expressions, Gronchi et al. found a reversed effect. A striking difference between the studies was the task performed by the participants. While in Wirth and Wentura, participants performed a discrimination task, they performed a location task in Gronchi et al. In Experiment 1, we directly compared the two versions of the dot-probe paradigm. With the discrimination task, the bias towards happy faces was replicated. However, the location task yielded a null effect. In Experiment 2, we found a cueing effect with an abrupt onset cue in both tasks. However, for the location task a congruence-sequence effect (a typical characteristic of response-priming processes) occurred. This result suggests that in the location task, attentional processes are confounded with response-priming processes. We recommend to generally use discrimination tasks.

Pareidolic faces receive prioritized attention in the dot-probe task

Face pareidolia occurs when random or ambiguous inanimate objects are perceived as faces. While real faces automatically receive prioritized attention compared with nonface objects, it is unclear whether pareidolic faces similarly receive special attention. We hypothesized that, given the evolutionary importance of broadly detecting animacy, pareidolic faces may have enough faceness to activate a broad face template, triggering prioritized attention. To test this hypothesis, and to explore where along the faceness continuum pareidolic faces fall, we conducted a series of dot-probe experiments in which we paired pareidolic faces with other images directly competing for attention: objects, animal faces, and human faces. We found that pareidolic faces elicited more prioritized attention than objects, a process that was disrupted by inversion, suggesting this prioritized attention was unlikely to be driven by low-level features. However, unexpectedly, pareidolic faces received more privileged attention compared with animal faces and showed similar prioritized attention to human faces. This attentional efficiency may be due to pareidolic faces being perceived as not only face-like, but also as human-like, and having larger facial features-eyes and mouths-compared with real faces. Together, our findings suggest that pareidolic faces appear automatically attentionally privileged, similar to human faces. Our findings are consistent with the proposal of a highly sensitive broad face detection system that is activated by pareidolic faces, triggering false alarms (i.e., illusory faces), which, evolutionarily, are less detrimental relative to missing potentially relevant signals (e.g., conspecific or heterospecific threats). In sum, pareidolic faces appear "special" in attracting attention.

No Evidence for Biased Attention Towards Emotional Scenes in Bornean Orangutans (Pongo pygmaeus)

Attention may be swiftly and automatically tuned to emotional expressions in social primates, as has been demonstrated in humans, bonobos, and macaques, and with mixed evidence in chimpanzees, where rapid detection of emotional expressions is thought to aid in navigating their social environment. Compared to the other great apes, orangutans are considered semi-solitary, but still form temporary social parties in which sensitivity to others' emotional expressions may be beneficial. The current study investigated whether implicit emotion-biased attention is also present in orangutans (Pongo pygmaeus). We trained six orangutans on the dot-probe paradigm: an established paradigm used in comparative studies which measures reaction time in response to a probe replacing emotional and neutral stimuli. Emotional stimuli consisted of scenes depicting conspecifics having sex, playing, grooming, yawning, or displaying aggression. These scenes were contrasted with neutral scenes showing conspecifics with a neutral face and body posture. Using Bayesian mixed modeling, we found no evidence for an overall emotion bias in this species. When looking at emotion categories separately, we also did not find substantial biases. We discuss the absence of an implicit attention bias for emotional expressions in orangutans in relation to the existing primate literature, and the methodological limitations of the task. Furthermore, we reconsider the emotional stimuli used in this study and their biological relevance.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s42761-022-00158-x.

Experiences of maltreatment in childhood and attention to facial emotions in healthy young women

Using reaction-time measures, research on the relationship between childhood maltreatment and biased attention to emotional stimuli in adults has obtained inconsistent results. To help clarify this issue, we conducted an eye-tracking study on the link between childhood maltreatment and allocation of attention to facial emotions analyzing gaze behavior in addition to manual reactions. In contrast to prior investigations, we excluded individuals with tendencies to minimize maltreatment experiences from analyses. Gaze behavior and manual response time of 58 healthy women were examined in a dot-probe task in which pairs of emotional (happy, sad, or disgusted) and neutral faces were presented. In our analyses, participants’ affectivity, level of alexithymia, and intelligence were controlled. Entry time and dwell time on facial expressions were used as indicators of attention allocation. Childhood maltreatment showed no effect on response latencies but was associated with shorter entry times on emotional faces and shorter dwell time on disgusted faces. Experiences of childhood maltreatment seem to be linked to an increased early vigilance to emotional social signals and to an attentional avoidance of hostile facial expressions at a later stage of perception. The present results suggest a vigilance-avoidance pattern of attention allocation associated with childhood maltreatment.

The Study of Security Priming on Avoidant Attentional Biases: Combining Microsaccadic Eye-Movement Measurement With a Dot-Probe Task

Microsaccades are small fixational eye movements that have shown to index covert attentional shifts. The present experiment combined microsaccades with performance measures from a dot-probe task to study influences of attachment security priming on the attentional biases of individuals high in attachment avoidance. Security priming is an experimental manipulation aimed at boosting felt security. Using a randomized, mixed design, we measured differences in attentional vigilance toward angry and neutral faces as a function of priming (neutral vs. secure) and attachment avoidance. Individuals high in avoidance habitually tend to withdraw from, or otherwise dismiss, emotionally salient stimuli. Here, we operationalized attentional withdrawal based on both task performance in the dot-probe task and microsaccadic movements. In addition, unlike previous studies where priming salience for the individual participant has been unclear, we used a standardized narrative method for attachment script assessment, securing an indication of how strongly each participant was primed. Dot-probe data significantly captured the link between avoidance and attentional disengagement, though from all facial stimuli (angry and neutral). Although microsaccadic movements did not capture avoidant attentional disengagement, they positively correlated to dot-probe data suggesting measurement convergence. Avoidance was associated with weaker security priming and no overall effect of priming on attention was found, indicating a need for further exploration of suitable priming methods to bypass avoidant deactivation. Our results provide a first indication that, as an implicit looking measure, microsaccadic movements can potentially reveal where early attention is directed at the exact moment of stimulus presentation.

It occurs after all: Attentional bias towards happy faces in the dot-probe task

Many studies have shown that not only threatening but also positive stimuli capture visual attention. However, in the dot-probe task, a common paradigm to assess attention to emotional stimuli, usually no bias towards happy faces occurs. Here, we investigated whether such a bias can occur and, if so, under which conditions. In Experiment 1, we investigated whether the bias is contingent on the simultaneous presentation of distractor stimuli with the targets. Participants performed a dot-probe task with either stand-alone targets or targets that were accompanied by distractors. We found an attentional bias towards happy faces that was not moderated by target type. To rule out perceptual low-level confounds as the cause of the bias towards happy faces, Experiments 2a and 2b comprised dot-probe tasks with inverted face cues. No attentional bias towards inverted happy faces occurred. In Experiment 3, we investigated whether a bias towards happy faces is contingent on a social-processing mode. Participants performed a dot-probe task with socially meaningful (schematic faces) or socially meaningless (scrambled schematic faces) targets. Again, a bias towards happy faces, which was not moderated by target type, occurred. In Experiment 4, we investigated the attentional bias towards happy faces when another highly relevant expression was present. Participants performed a dot-probe task with both happy and angry face cues. A significant attentional bias towards emotional faces occurred that did not differ between both cue emotions. These results suggest that happy faces are sufficiently relevant for observers to capture attention in the dot-probe task.

General and own-species attentional face biases

Humans demonstrate enhanced processing of human faces compared with animal faces, known as own-species bias. This bias is important for identifying people who may cause harm, as well as for recognizing friends and kin. However, growing evidence also indicates a more general face bias. Faces have high evolutionary importance beyond conspecific interactions, as they aid in detecting predators and prey. Few studies have explored the interaction of these biases together. In three experiments, we explored processing of human and animal faces, compared with each other and to nonface objects, which allowed us to examine both own-species and broader face biases. We used a dot-probe paradigm to examine human adults' covert attentional biases for task-irrelevant human faces, animal faces, and objects. We replicated the own-species attentional bias for human faces relative to animal faces. We also found an attentional bias for animal faces relative to objects, consistent with the proposal that faces broadly receive privileged processing. Our findings suggest that humans may be attracted to a broad class of faces. Further, we found that while participants rapidly attended to human faces across all cue display durations, they attended to animal faces only when they had sufficient time to process them. Our findings reveal that the dot-probe paradigm is sensitive for capturing both own-species and more general face biases, and that each has a different attentional signature, possibly reflecting their unique but overlapping evolutionary importance.

Attentional bias towards negative stimuli in healthy individuals and the effects of trait anxiety

This study aimed to investigate the time course of attentional bias for negative information in healthy individuals and to assess the associated influence of trait anxiety. Thirty-eight healthy volunteers performed an emotional dot-probe task with pairs of negative and neutral scenes, presented for either 1 or 2 s and followed by a target placed at the previous location of either negative or neutral stimulus. Analyses included eye movements during the presentation of the scenes and response times associated with target localization. In a second step, analyses focused on the influence of trait anxiety. While there was no significant difference at the behavioral level, the eye-tracking data revealed that negative information held longer attention than neutral stimuli once fixated. This initial maintenance bias towards negative pictures then increased with increasing trait anxiety. However, at later processing stages, only individuals with the highest trait anxiety appeared to fixate longer on negative pictures than neutral pictures, individuals with low trait anxiety showing the opposite pattern. This study provides novel evidence that healthy individuals display an attentional maintenance bias towards negative stimuli, which is associated with trait anxiety.

Weight Status and Attentional Biases Toward Foods: Impact of Implicit Olfactory Priming

Objective: Numerous studies highlight the involvement of cognitive factors in the development and maintenance of obesity. We aimed to measure attentional biases (AB) toward foods (i.e., the individual tendency to automatically orient one's attention toward food stimuli) in normal-weight (NW) individuals and those with overweight (OW) and obesity (OB). We evaluated whether implicit or explicit exposure to olfactory food cues could modify AB. Methods: Eighty-five participants with different weight statuses took part in this experiment. We measured AB toward food pictures with an adapted visual probe task and the variations in AB, while participants were primed with olfactory food cues (within-subject design: no odor/low-energy dense food odor/high-energy dense food odor). Odors were non-attentively perceived during session 1 (implicit condition) and attentively perceived during session 2 (explicit condition). Results: Our results highlighted AB toward food pictures, especially when foods were energy dense, regardless of weight status (p < 0.001). The olfactory priming effect was only significant in the implicit condition. Participants with obesity had a stronger AB toward foods when they were primed with a non-attentively perceived high-energy dense food odor than with a non-attentively perceived low-energy dense food odor (p = 0.02). The trend was reversed for normal-weight participants, while no significant effect was found for participants with overweight. Conclusion: Our results support the hypothesis that an obesity-specific cognitive vulnerability may influence the processing of food-related stimuli and only while food cues are non-attentively perceived. Future research should seek to understand the mechanisms of this phenomenon.

Attentional bias towards angry faces is moderated by the activation of a social processing mode in the general population

Dot-probe studies usually find an attentional bias towards threatening stimuli only in anxious participants, but not in non-anxious participants. In the present study, we conducted two experiments to investigate whether attentional bias towards angry faces in unselected samples is moderated by the extent to which the current task requires social processing. In Experiment 1, participants performed a dot-probe task involving classification of either socially meaningful targets (schematic faces) or meaningless targets (scrambled schematic faces). Targets were preceded by two photographic face cues, one angry and one neutral. Angry face cues only produced significant cueing scores (i.e. faster target responses if the target replaced the angry face compared to the neutral face) with socially meaningful targets, not with meaningless targets. In Experiment 2, participants classified only meaningful targets, which were either socially meaningful (schematic faces) or not (schematic houses). Again, mean cueing scores were significantly moderated by the social character of the targets. However, cueing scores in this experiment were non-significant in the social target condition and significantly negative in the non-social target condition. These results suggest that attentional bias towards angry faces in the dot-probe task is moderated by the activation of a social processing mode in unselected samples.

Furious snarling: Teeth-exposure and anxiety-related attentional bias towards angry faces

Dot-probe studies consistently show that high trait anxious individuals have an attentional bias towards threatening faces. However, little is known about the influence of perceptual confounds of specific emotional expressions on this effect. Teeth-exposure was recently recognized as an important factor for the occurrence of attentional bias towards angry faces in a closely related paradigm (the face-in-the-crowd paradigm). Therefore, we investigated the effect of exposed teeth on attentional bias towards angry faces in the dot-probe task. Participants (N = 74) were asked to classify probe stimuli that were preceded by two simultaneously presented face cues, one angry and the other neutral. Half of the angry faces had exposed teeth, the other half had concealed teeth. Afterwards, participants completed the trait anxiety scale of the STAI. For angry faces with non-exposed teeth, we found the expected positive correlation (r = .441) of trait anxiety with the attentional bias score (reaction times for probes replacing the neutral face minus reaction times for probes replacing the angry face). However, we found no influence of trait anxiety on attentional bias towards angry faces with exposed teeth. These results suggest that natural low-level stimulus confounds of emotional faces like exposed teeth can affect the manifestation of anxiety-related attentional biases towards angry faces in the dot-probe task.

Temporal dynamics in attention bias: effects of sex differences, task timing parameters, and stimulus valence

New methods of calculating indices from the dot-probe task measure temporal dynamics in attention bias or fluctuations in attention bias towards and away from emotional stimuli over time. However, it is unclear how task-specific parameters such as stimulus valence and stimulus onset asynchrony (SOA) as well as participant sex affect temporal dynamics in attention bias. To address this, male and female participants (N = 106) completed either a fearful or happy face dot-probe task with four levels of SOA (84 ms, 168 ms, 336 ms, and 672 ms). Results suggest that temporal dynamics in attention bias are (1) greatest at the longest SOA, (2) greater in females, and (3) insensitive to stimulus valence. These findings indicate that participant sex and task timing, but not stimulus valence, are related to temporal dynamics in attention bias and should be considered in future studies utilizing this approach.

The dot-probe task to measure emotional attention: A suitable measure in comparative studies?

For social animals, attending to and recognizing the emotional expressions of other individuals is of crucial importance for their survival and likely has a deep evolutionary origin. Gaining insight into how emotional expressions evolved as adaptations over the course of evolution can be achieved by making direct cross-species comparisons. To that extent, experimental paradigms that are suitable for investigating emotional processing across species need to be developed and evaluated. The emotional dot-probe task, which measures attention allocation toward emotional stimuli, has this potential. The task is implicit, and subjects need minimal training to perform the task successfully. Findings in nonhuman primates, although scarce, show that they, like humans, have an attentional bias toward emotional stimuli. However, the wide literature on human studies has shown that different factors can have important moderating effects on the results. Due to the large heterogeneity of this literature, these moderating effects often remain unnoticed. We here review this literature and show that subject characteristics and differences in experimental designs affect the results of the dot-probe task. We conclude with specific recommendations regarding these issues that are particularly relevant to take into consideration when applying this paradigm to study animals.

Attentional bias to threat in the general population is contingent on target competition, not on attentional control settings

Dot-probe studies usually find an attentional bias towards threatening stimuli only in anxious participants. Here, we investigated under what conditions such a bias occurs in unselected samples. According to contingent-capture theory, an irrelevant cue only captures attention if it matches an attentional control setting. Therefore, we first tested the hypothesis that an attentional control setting tuned to threat must be activated in (non-anxious) individuals. In Experiment 1, we used a dot-probe task with a manipulation of attentional control settings ('threat' - set vs. control set). Surprisingly, we found an (anxiety-independent) attentional bias to angry faces that was not moderated by attentional control settings. Since we presented two stimuli (i.e., a target and a distractor) on the target screen in Experiment 1 (a necessity to realise the test of contingent capture), but most dot-probe studies only employ a single target, we conducted Experiment 2 to test the hypothesis that attentional bias in the general population is contingent on target competition. Participants performed a dot-probe task, involving presentation of a stand-alone target or a target competing with a distractor. We found an (anxiety-independent) attentional bias towards angry faces in the latter but not the former condition. This suggests that attentional bias towards angry faces in unselected samples is not contingent on attentional control settings but on target competition.

Event-related potentials of attentional bias toward faces in the dot-probe task: A systematic review

The dot-probe task is a common task to assess attentional bias toward different stimuli and how groups differ (e.g., attentional bias in anxiety disorders). However, measuring reaction time has been suggested to be unreliable. Neuroimaging methods such as fMRI were shown to be more reliable in assessing attentional bias, but fMRI has poor temporal resolution and therefore cannot assess timing of attention. ERPs have been used to examine the time course of attentional bias. Although ERP research may be more reliable than reaction time, there have been inconsistencies in the literature. This review systematically searched for articles that used the dot-probe task with facial expressions and measured neural correlates with ERP. We found that some of the inconsistencies might be the cause of methodological differences (e.g., timing of stimuli), differences in emotional expression, and/or sample differences (e.g., sex, age, etc.). Suggestions on how future research could address the issues presented in this review were discussed.

The human body odor compound androstadienone leads to anger-dependent effects in an emotional Stroop but not dot-probe task using human faces

The androgen derivative androstadienone is a substance found in human sweat and thus is a putative human chemosignal. Androstadienone has been studied with respect to effects on mood states, attractiveness ratings, physiological and neural activation. With the current experiment, we aimed to explore in which way androstadienone affects attention to social cues (human faces). Moreover, we wanted to test whether effects depend on specific emotions, the participants' sex and individual sensitivity to smell androstadienone. To do so, we investigated 56 healthy individuals (thereof 29 females taking oral contraceptives) with two attention tasks on two consecutive days (once under androstadienone, once under placebo exposure in pseudorandomized order). With an emotional dot-probe task we measured visuo-spatial cueing while an emotional Stroop task allowed us to investigate interference control. Our results suggest that androstadienone acts in a sex, task and emotion-specific manner as a reduction in interference processes in the emotional Stroop task was only apparent for angry faces in men under androstadienone exposure. More specifically, men showed a smaller difference in reaction times for congruent compared to incongruent trials. At the same time also women were slightly affected by smelling androstadienone as they classified angry faces more often correctly under androstadienone. For the emotional dot-probe task no modulation by androstadienone was observed. Furthermore, in both attention paradigms individual sensitivity to androstadienone was neither correlated with reaction times nor error rates in men and women. To conclude, exposure to androstadienone seems to potentiate the relevance of angry faces in both men and women in connection with interference control, while processes of visuo-spatial cueing remain unaffected.

Capturing Dynamics of Biased Attention: Are New Attention Variability Measures the Way Forward?

Background

New indices, calculated on data from the widely used Dot Probe Task, were recently proposed to capture variability in biased attention allocation. We observed that it remains unclear which data pattern is meant to be indicative of dynamic bias and thus to be captured by these indices. Moreover, we hypothesized that the new indices are sensitive to SD differences at the response time (RT) level in the absence of bias.

Method

Randomly generated datasets were analyzed to assess properties of the Attention Bias Variability (ABV) and Trial Level Bias Score (TL-BS) indices. Sensitivity to creating differences in 1) RT standard deviation, 2) mean RT, and 3) bias magnitude were assessed. In addition, two possible definitions of dynamic attention bias were explored by creating differences in 4) frequency of bias switching, and 5) bias magnitude in the presence of constant switching.

Results

ABV and TL-BS indices were found highly sensitive to increasing SD at the response time level, insensitive to increasing bias, linearly sensitive to increasing bias magnitude in the presence of bias switches, and non-linearly sensitive to increasing the frequency of bias switches. The ABV index was also found responsive to increasing mean response times in the absence of bias.

Conclusion

Recently proposed DPT derived variability indices cannot uncouple measurement error from bias variability. Significant group differences may be observed even if there is no bias present in any individual dataset. This renders the new indices in their current form unfit for empirical purposes. Our discussion focuses on fostering debate and ideas for new research to validate the potentially very important notion of biased attention being dynamic.

Relevance drives attention: Attentional bias for gain- and loss-related stimuli is driven by delayed disengagement

Attentional bias to gain- and loss-related stimuli was investigated in a dot-probe task. We used coloured stimuli that had acquired their valence during the experiment by signalling the chance to either win or lose points in a game task. Replicating previous findings with the additional singleton paradigm, we found attentional bias effects for both gain- and loss-related colours. The effects were due to delayed disengagement from valent stimuli, especially if they were positive, and could not be explained by nonattentional processes like behavioural freezing. Our findings suggest that stimuli signalling opportunities and dangers hold attention, supporting a general motivational relevance principle of the orienting of attention.