Paola Ricciardelli

Are visual stimuli sufficient to evoke motor information?: Studies with hand primes

In two experiments we assessed whether seeing objects automatically activates information regarding how to manipulate them. In Experiment 1 participants categorized photographs of objects that could be manipulated either with a power or a precision grip into artefacts or natural kinds. Target-objects were preceded by primes consisting of photographs of hands in grasping postures (precision or power grip). Experiment 2 involved a preliminary motor training phase in which each visual prime was associated with the actual motor action. In both experiments, natural kinds graspable with a power grip produced the fastest responses. In Experiment 2 we also found a congruency effect between the prime and the kind of grip required by the object (precision, power). Results suggest that visual stimuli automatically activate motor information. Specific motor programs are, however, activated only if motor training is performed before the categorization task. Implications of the results for the understanding of the organization of conceptual and motor information in the brain are discussed.

Effects of head orientation on gaze perception: How positive congruency effects can be reversed

Several past studies have considered how perceived head orientation may be combined with perceived gaze direction in judging where someone else is attending. In three experiments we tested the impact of different sources of information by examining the role of head orientation in gaze-direction judgements when presenting: (a) the whole face; (b) the face with the nose masked; (c) just the eye region, removing all other head-orientation cues apart from some visible part of the nose; or (d) just the eyes, with all parts of the nose masked and no head orientation cues present other than those within the eyes themselves. We also varied time pressure on gaze direction judgements. The results showed that gaze judgements were not solely driven by the eye region. Gaze perception can also be affected by parts of the head and face, but in a manner that depends on the time constraints for gaze direction judgements. While “positive” congruency effects were found with time pressure (i.e., faster left/right judgements of seen gaze when the seen head deviated towards the same side as that gaze), the opposite applied without time pressure.

Positive and negative gaze perception in autism spectrum conditions

Abstract Eyes are key social features providing a wealth of information about the attention, interest, emotion, and intention of others. Humans are typically very adept at detecting gaze direction, but there is a large decrement in gaze discrimination ability when eye images change from positive to negative polarity. This is thought to show an expert system for gaze perception that applies a contrast-specific heuristic to determine where someone else is looking. Autism spectrum conditions (ASC) are characterized by social deficits including difficulties in face-processing and in the social use of gaze. People with ASC are thought to have less expertise for gaze processing compared to typical controls, though little research has tested this. We investigated gaze direction perception in typical males and females, and males with ASC using facial stimuli with positive or negative polarity of the eyes. Results showed that the ASC group was worse at judging gaze direction with positive stimuli, and showed less of a decrement in performance when eye stimuli changed from positive to negative polarity. The differences in gaze perception for the ASC group were most evident when information from the eyes was more difficult and ambiguous. Typical females performed better at gaze direction detection with positive polarity than typical males, who in turn performed better than males with ASC. This latter finding is consistent with the extreme male brain theory of autism, and with the idea that people with ASC have less gaze expertise.

Is gaze following purely reflexive or goal-directed instead? Revisiting the automaticity of orienting attention by gaze cues

Distracting gaze has been shown to elicit automatic gaze following. However, it is still debated whether the effects of perceived gaze are a simple automatic spatial orienting response or are instead sensitive to the context (i.e. goals and task demands). In three experiments, we investigated the conditions under which gaze following occurs. Participants were instructed to saccade towards one of two lateral targets. A face distracter, always present in the background, could gaze towards: (a) a task-relevant target––(“matching” goal-directed gaze shift)––congruent or incongruent with the instructed direction, (b) a task-irrelevant target, orthogonal to the one instructed (“non-matching” goal-directed gaze shift), or (c) an empty spatial location (no-goal-directed gaze shift). Eye movement recordings showed faster saccadic latencies in correct trials in congruent conditions especially when the distracting gaze shift occurred before the instruction to make a saccade. Interestingly, while participants made a higher proportion of gaze-following errors (i.e. errors in the direction of the distracting gaze) in the incongruent conditions when the distracter’s gaze shift preceded the instruction onset indicating an automatic gaze following, they never followed the distracting gaze when it was directed towards an empty location or a stimulus that was never the target. Taken together, these findings suggest that gaze following is likely to be a product of both automatic and goal-driven orienting mechanisms.

Is there a direct link between gaze perception and joint attention behaviours? Effects of gaze contrast polarity on oculomotor behaviour

Previous studies have found that attention is oriented in the direction of other people’s gaze suggesting that gaze perception is related to the mechanisms of joint attention. However, the role of the perception of gaze direction on joint attention has been challenged. We investigated the effects of disrupting gaze perception on the orienting of observers’ attention, in particular, whether orienting to gaze direction is affected by the disruptive effect of negative contrast polarity on gaze perception. A dynamic distracting gaze was presented to observers performing an endogenous saccadic task. Gaze perception was manipulated by reversing the contrast polarity between the sclera and the iris. With positive display polarity, eye movement recordings showed shorter saccadic latencies when the direction of the instructed saccade matched the direction of the distracting gaze, and a substantial number of erroneous saccades towards the direction of the perceived gaze when the latter did not match the instruction. Crucially, such effects were not found when gaze contrast polarity was reversed and gaze perception was impaired. These results extend previous studies by demonstrating the existence of a direct link between joint attention and the perception of gaze direction, and show how orienting of attention to other people’s gaze can be suppressed.

Face age modulates gaze following in young adults

Gaze-following behaviour is considered crucial for social interactions which are influenced by social similarity. We investigated whether the degree of similarity, as indicated by the perceived age of another person, can modulate gaze following. Participants of three different age-groups (18–25; 35–45; over 65) performed an eye movement (a saccade) towards an instructed target while ignoring the gaze-shift of distracters of different age-ranges (6–10; 18–25; 35–45; over 70). The results show that gaze following was modulated by the distracter face age only for young adults. Particularly, the over 70 year-old distracters exerted the least interference effect. The distracters of a similar age-range as the young adults (18–25; 35–45) had the most effect, indicating a blurred own-age bias (OAB) only for the young age group. These findings suggest that face age can modulate gaze following, but this modulation could be due to factors other than just OAB (e.g., familiarity).

How do we update faces? Effects of gaze direction and facial expressions on working memory updating.

The aim of the study was to investigate how the biological binding between different facial dimensions, and their social and communicative relevance, may impact updating processes in working memory (WM). We focused on WM updating because it plays a key role in ongoing processing. Gaze direction and facial expression are crucial and changeable components of face processing. Direct gaze enhances the processing of approach-oriented facial emotional expressions (e.g., joy), while averted gaze enhances the processing of avoidance-oriented facial emotional expressions (e.g., fear). Thus, the way in which these two facial dimensions are combined communicates to the observer important behavioral and social information. Updating of these two facial dimensions and their bindings has not been investigated before, despite the fact that they provide a piece of social information essential for building and maintaining an internal ongoing representation of our social environment. In Experiment 1 we created a task in which the binding between gaze direction and facial expression was manipulated: high binding conditions (e.g., joy-direct gaze) were compared to low binding conditions (e.g., joy-averted gaze). Participants had to study and update continuously a number of faces, displaying different bindings between the two dimensions. In Experiment 2 we tested whether updating was affected by the social and communicative value of the facial dimension binding; to this end, we manipulated bindings between eye and hair color, two less communicative facial dimensions. Two new results emerged. First, faster response times were found in updating combinations of facial dimensions highly bound together. Second, our data showed that the ease of the ongoing updating processing varied depending on the communicative meaning of the binding that had to be updated. The results are discussed with reference to the role of WM updating in social cognition and appraisal processes.

Gaze direction and facial expressions exert combined but different effects on attentional resources

Gaze direction and facial expressions are critical components of face processing and have been shown to influence attention deployment. We investigated whether gaze direction (direct vs. averted) combined with a neutral or angry expression modulates the deployment of attentional resources over time. In a Rapid Serial Visual Presentation (RSVP) paradigm participants had to decide the gender of a neutral or an angry target face with direct or averted gaze (T1) and then to judge the orientation of a target picture of a landscape (T2), following the face at different time intervals. Results showed no attentional blink effect (i.e., no deterioration in T2 accuracy) when T1 was an angry face with direct gaze, whereas it was present for angry faces with averted gaze or neutral faces with either averted or direct gaze. These findings are consistent with appraisal theories and are discussed against the background of automatic processing of threat stimuli.

Can we resist another person’s gaze?

Adaptive adjustments of strategies are needed to optimize behavior in a dynamic and uncertain world. A key function in implementing flexible behavior and exerting self-control is represented by the ability to stop the execution of an action when it is no longer appropriate for the environmental requests. Importantly, stimuli in our environment are not equally relevant and some are more valuable than others. One example is the gaze of other people, which is known to convey important social information about their direction of attention and their emotional and mental states. Indeed, gaze direction has a significant impact on the execution of voluntary saccades of an observer since it is capable of inducing in the observer an automatic gaze-following behavior: a phenomenon named social or joint attention. Nevertheless, people can exert volitional inhibitory control on saccadic eye movements during their planning. Little is known about the interaction between gaze direction signals and volitional inhibition of saccades. To fill this gap, we administered a countermanding task to 15 healthy participants in which they were asked to observe the eye region of a face with the eyes shut appearing at central fixation. In one condition, participants were required to suppress a saccade, that was previously instructed by a gaze shift toward one of two peripheral targets, when the eyes were suddenly shut down (social condition, SC). In a second condition, participants were asked to inhibit a saccade, that was previously instructed by a change in color of one of the two same targets, when a change of color of a central picture occurred (non-social condition, N-SC). We found that inhibitory control was more impaired in the SC, suggesting that actions initiated and stopped by social cues conveyed by the eyes are more difficult to withhold. This is probably due to the social value intrinsically linked to these cues and the many uses we make of them.

Emotion recognition through static faces and moving bodies: a comparison between typically developed adults and individuals with high level of autistic traits

We investigated whether the type of stimulus (pictures of static faces vs. body motion) contributes differently to the recognition of emotions. The performance (accuracy and response times) of 25 Low Autistic Traits (LAT group) young adults (21 males) and 20 young adults (16 males) with either High Autistic Traits or with High Functioning Autism Spectrum Disorder (HAT group) was compared in the recognition of four emotions (Happiness, Anger, Fear, and Sadness) either shown in static faces or conveyed by moving body patch-light displays (PLDs). Overall, HAT individuals were as accurate as LAT ones in perceiving emotions both with faces and with PLDs. Moreover, they correctly described non-emotional actions depicted by PLDs, indicating that they perceived the motion conveyed by the PLDs per se. For LAT participants, happiness proved to be the easiest emotion to be recognized: in line with previous studies we found a happy face advantage for faces, which for the first time was also found for bodies (happy body advantage). Furthermore, LAT participants recognized sadness better by static faces and fear by PLDs. This advantage for motion kinematics in the recognition of fear was not present in HAT participants, suggesting that (i) emotion recognition is not generally impaired in HAT individuals, (ii) the cues exploited for emotion recognition by LAT and HAT groups are not always the same. These findings are discussed against the background of emotional processing in typically and atypically developed individuals.