Non-invasive primate head restraint using thermoplastic masks

BACKGROUND

The success of many neuroscientific studies depends upon adequate head fixation of awake, behaving animals. Typically, this is achieved by surgically affixing a head-restraint prosthesis to the skull.

NEW METHOD

Here we report the use of thermoplastic masks to non-invasively restrain monkeys' heads. Mesh thermoplastic sheets become pliable when heated and can then be molded to an individual monkey's head. After cooling, the custom mask retains this shape indefinitely for day-to-day use.

RESULTS

We successfully trained rhesus macaques (Macaca mulatta) to perform cognitive tasks while wearing thermoplastic masks. Using these masks, we achieved a level of head stability sufficient for high-resolution eye-tracking and intracranial electrophysiology.

COMPARISON WITH EXISTING METHOD

Compared with traditional head-posts, we find that thermoplastic masks perform at least as well during infrared eye-tracking and single-neuron recordings, allow for clearer magnetic resonance image acquisition, enable freer placement of a transcranial magnetic stimulation coil, and impose lower financial and time costs on the lab.

CONCLUSIONS

We conclude that thermoplastic masks are a viable non-invasive form of primate head restraint that enable a wide range of neuroscientific experiments.

Linguistic labels, dynamic visual features, and attention in infant category learning

How do words affect categorization? According to some accounts, even early in development words are category markers and are different from other features. According to other accounts, early in development words are part of the input and are akin to other features. The current study addressed this issue by examining the role of words and dynamic visual features in category learning in 8- to 12-month-old infants. Infants were familiarized with exemplars from one category in a label-defined or motion-defined condition and then tested with prototypes from the studied category and from a novel contrast category. Eye-tracking results indicated that infants exhibited better category learning in the motion-defined condition than in the label-defined condition, and their attention was more distributed among different features when there was a dynamic visual feature compared with the label-defined condition. These results provide little evidence for the idea that linguistic labels are category markers that facilitate category learning.

Eyetracking of social preference choices reveals normal but faster processing in autism

People with Autism Spectrum Disorder (ASD) have been reported to show atypical attention and evaluative processing, in particular for social stimuli such as faces. The usual measure in these studies is an explicit, subjective judgment, which is the culmination of complex-temporally extended processes that are not typically dissected in detail. Here we addressed a neglected aspect of social decision-making in order to gain further insight into the underlying mechanisms: the temporal evolution of the choice. We investigated this issue by quantifying the alternating patterns of gaze onto faces, as well as nonsocial stimuli, while subjects had to decide which of the two stimuli they preferred. Surprisingly, the temporal profile of fixations relating to choice (the so-called "gaze cascade") was entirely normal in ASD, as were the eventual preference choices. Despite these similarities, we found two key abnormalities: people with ASD made choices more rapidly than did control subjects across the board, and their reaction times for social preference judgments were insensitive to choice difficulty. We suggest that ASD features an altered decision-making process when basing choice on social preferences. One hypothesis motivated by these data is that a choice criterion is reached in ASD regardless of the discriminability of the options.

Informational constraints on spontaneous visuomotor entrainment

Past research has revealed that an individual's rhythmic limb movements become spontaneously entrained to an environmental rhythm if visual information about the rhythm is available and its frequency is near that of the individual's movements. Research has also demonstrated that if the eyes track an environmental stimulus, the spontaneous entrainment to the rhythm is strengthened. One hypothesis explaining this enhancement of spontaneous entrainment is that the limb movements and eye movements are linked through a neuromuscular coupling or synergy. Another is that eye-tracking facilitates the pick up of important coordinating information. Experiment 1 investigated the first hypothesis by evaluating whether any rhythmic movement of the eyes would facilitate spontaneous entrainment. Experiments 2 and 3 (respectively) explored whether eye-tracking strengthens spontaneous entrainment by allowing the pickup of trajectory direction change information or allowing an increase in the amount of information to be picked-up. Results suggest that the eye-tracking enhancement of spontaneous entrainment is a consequence of increasing the amount of information available to be picked-up.

Task constraints distinguish perspective inferences from perspective use during discourse interpretation in a false belief task

Interpreting other peoples' actions relies on an understanding of their current mental states (e.g. beliefs, desires and intentions). In this paper, we distinguish between listeners' ability to infer others' perspectives and their explicit use of this knowledge to predict subsequent actions. In a visual-world study, two groups of participants (passive observers vs. active participants) watched short videos, depicting transfer events, where one character ('Jane') either held a true or false belief about an object's location. We tracked participants' eye-movements around the final visual scene, time-locked to related auditory descriptions (e.g. "Jane will look for the chocolates in the container on the left".). Results showed that active participants had already inferred the character's belief in the 1s preview period prior to auditory onset, before it was possible to use this information to predict an outcome. Moreover, they used this inference to correctly anticipate reference to the object's initial location on false belief trials at the earliest possible point (i.e. from "Jane" onwards). In contrast, passive observers only showed evidence of a belief inference from the onset of "Jane", and did not show reliable use of this inference to predict Jane's behaviour on false belief trials until much later, when the location ("left/right") was auditorily available. These results show that active engagement in a task activates earlier inferences about others' perspectives, and drives immediate use of this information to anticipate others' actions, compared to passive observers, who are susceptible to influences from egocentric or reality biases. Finally, we review evidence that using other peoples' perspectives to predict their behaviour is more cognitively effortful than simply using one's own.

The effects of visual context and individual differences on perception and evaluation of modern art and graffiti art

Traditionally, artworks are seen as autonomous objects that stand (or should stand) on their own. However, at least since the emergence of Conceptual Art in the 1920s and Pop Art in the 1960s, art lacks any distinctive perceptual features that define it as such. Art, therefore, cannot be defined without reference to its context. Some studies have shown that context affects the evaluation of artworks, and that specific contexts (street for graffiti art, museum for modern art) elicit specific effects (Gartus & Leder, 2014). However, it is yet unclear how context changes perception and appreciation processes. In our study we measured eye-movements while participants (64 psychology undergraduates, 48% women) perceived and evaluated beauty, interest, emotional valence, as well as perceived style for modern art and graffiti art embedded into either museum or street contexts. For modern art, beauty and interest ratings were higher in a museum than in a street context, but context made no difference for the ratings of graffiti art. Importantly, we also found an interaction of context and individual interest in graffiti for beauty and interest ratings, as well as for number of fixations. Analyses of eye-movements also revealed that viewing times were in general significantly longer in museum than in street contexts. We conclude that context can have an important influence on aesthetic appreciation. However, some effects depend also on the style of the artworks and the individual art interests of the viewers.

Double attention bias for positive and negative emotional faces in clinical depression: evidence from an eye-tracking study

BACKGROUND AND OBJECTIVES

According to cognitive models, attentional biases in depression play key roles in the onset and subsequent maintenance of the disorder. The present study examines the processing of emotional facial expressions (happy, angry, and sad) in depressed and non-depressed adults.

METHODS

Sixteen unmedicated patients with Major Depressive Disorder (MDD) and 34 never-depressed controls (ND) completed an eye-tracking task to assess different components of visual attention (orienting attention and maintenance of attention) in the processing of emotional faces.

RESULTS

Compared to ND, participants with MDD showed a negative attentional bias in attentional maintenance indices (i.e. first fixation duration and total fixation time) for sad faces. This attentional bias was positively associated with the severity of depressive symptoms. Furthermore, the MDD group spent a marginally less amount of time viewing happy faces compared with the ND group. No differences were found between the groups with respect to angry faces and orienting attention indices.

LIMITATIONS

The current study is limited by its cross-sectional design.

CONCLUSIONS

These results support the notion that attentional biases in depression are specific to depression-related information and that they operate in later stages in the deployment of attention.

Which psychotic experiences are associated with a need for clinical care?

BACKGROUND

The aims of this study were to identify (1) the factor structure of anomalous experiences across the psychosis continuum; (2) qualitative and quantitative differences in psychotic experiences (PEs) between "non need-for-care" and two clinical groups: psychosis patients and individuals at ultra high risk (UHR) of psychosis. We aimed to distinguish which types of experiences would be related to malign (need-for-care and/or help-seeking) versus benign outcomes.

METHODS

Component scores obtained from a Principal Components Analysis of PEs from lifetime scores on the Appraisals of Anomalous Experience Inventory (Brett et al., 2007) were compared across 96 participants: patients diagnosed with a psychotic disorder (n=37), help-seeking UHR people (n=21), and non-clinical individuals presenting with enduring PEs (n=38).

RESULTS

A five-component structure provided the best solution, comprising dissociative-type experiences, subjective cognitive deficits, and three separate components relating to "positive" symptoms. All groups reported "positive" experiences, such as ideas of reference and hallucinations, with the non-clinical group displaying more PEs in the Paranormal/Hallucinatory component than both clinical groups. "Cognitive/Attentional anomalies" was the only component where the clinical groups reported significantly more anomalies than the non-clinical group. However psychosis patients reported more frequent first-rank type symptoms and "hypomanic" type PEs than the other groups.

DISCUSSION

"Positive" PEs were common across the psychosis spectrum, although first-rank type symptoms were particularly marked in participants diagnosed with a psychotic disorder. Help-seeking and need-for-care were associated with the presence of subjective cognitive disturbances. These findings suggest that anomalies of cognition and attention may be more relevant to poorer outcomes than the presence of anomalous experiences.

Excessive checking behavior during an image comparison task in schizophrenia

BACKGROUND

Patients with schizophrenia display significant working memory and executive deficits. In patients with obsessive-compulsive disorder (OCD), several studies suggest that working memory dysfunction may be one of the causes of compulsive checking behaviors. Hence, this study aimed at assessing whether patients with schizophrenia were impaired on an image comparison task used to measure checking behaviors, and whether the origin and profile of impairment on this task was different between schizophrenia and OCD.

METHODS

Eye movement recordings were used to assess the checking behavior of 24 patients with schizophrenia and 24 control participants who had to decide whether two images were different or identical. The verbal and visuo-spatial components of participants' working memory were measured using the reading span and backward location span tests.

RESULTS

Compared to controls, patients with schizophrenia had reduced working memory spans and showed excessive checking behavior when comparing the two images. However, the intensity of their checking behavior was not significantly related to their working memory deficits.

CONCLUSIONS

Several recent studies demonstrated that the excessive checking behaviors displayed by patients with OCD were related to working memory dysfunction. The absence of a relationship between the excessive checking behavior of patients with schizophrenia and their working memory deficits suggests that checking behaviors do not have the same origin in the two disorders.

A comparative study of sustained attentional bias on emotional processing in ADHD children to pictures with eye-tracking

OBJECTIVE

ADHD children have anomalous and negative behavior especially in emotionally related fields when compared to other. Evidence indicates that attention has an impact on emotional processing. The present study evaluates the effect of emotional processing on the sustained attention of children with ADHD type C.

MATERIALS & METHODS

Sixty participants form two equal groups (each with 30 children) of normal and ADHD children) and each subject met the required selected criterion as either a normal or an ADHD child. Both groups were aged from 6-11-years-old. All pictures were chosen from the International Affective Picture System (IAPS) and presented paired emotional and neutral scenes in the following categories: pleasant-neutral; pleasant-unpleasant; unpleasant-neutral; and neutral-neutral. Sustained attention was evaluated based on the number and duration of total fixation and was compared between the groups with MANOVA analysis.

RESULTS

The duration of sustained attention on pleasant in the pleasant-unpleasant pair was significant. Bias in duration of sustained attention on pleasant scenes in pleasant-neutral pairs is significantly different between the groups.

CONCLUSION

Such significant differences might be indicative of ADHD children deficiencies in emotional processing. It seems that the highly deep effect of emotionally unpleasant scenes to gain the focus of ADHD children's attention is responsible for impulsiveness and abnormal processing of emotional stimuli.

Immediate lexical integration of novel word forms

It is well known that familiar words inhibit each other during spoken word recognition. However, we do not know how and under what circumstances newly learned words become integrated with the lexicon in order to engage in this competition. Previous work on word learning has highlighted the importance of offline consolidation (Gaskell & Dumay, 2003) and meaning (Leach & Samuel, 2007) to establish this integration. In two experiments we test the necessity of these factors by examining the inhibition between newly learned items and familiar words immediately after learning. Participants learned a set of nonwords without meanings in active (Experiment 1) or passive (Experiment 2) exposure paradigms. After training, participants performed a visual world paradigm task to assess inhibition from these newly learned items. An analysis of participants' fixations suggested that the newly learned words were able to engage in competition with known words without any consolidation.

Orienting and maintenance of attention to threatening facial expressions in anxiety--an eye movement study

Cognitive models posit that anxiety disorders stem in part from underlying attentional biases to threat. Consistent with this, studies have found that the attentional bias to threat-related stimuli is greater in high vs. low anxious individuals. Nevertheless, it is not clear if similar biases exist for different threatening emotions or for any facial emotional stimulus. In the present study, we used eye-tracking to measure orienting and maintenance of attention to faces displaying anger, fear and disgust as threats, and faces displaying happiness and sadness. Using a free viewing task, we examined differences between low and high trait anxious (HTA) individuals in the attention they paid to each of these emotional faces (paired with a neutral face). We found that initial orienting was faster for angry and happy faces, and high trait anxious participants were more vigilant to fearful and disgust faces. Our results for attentional maintenance were not consistent. The results of the present study suggest that attentional processes may be more emotion-specific than previously believed. Our results suggest that attentional processes for different threatening emotions may not be the same and that attentional processes for some negative and some positive emotions may be similar.

Losing track of time? Processing of time reference inflection in agrammatic and healthy speakers of German

BACKGROUND

Individuals with agrammatic aphasia (IWAs) have problems with grammatical decoding of tense inflection. However, these difficulties depend on the time frame that the tense refers to. Verb morphology with reference to the past is more difficult than with reference to the non-past, because a link needs to be made to the past event in discourse, as captured in the PAst DIscourse LInking Hypothesis (PADILIH; Bastiaanse, R., Bamyaci, E., Hsu, C., Lee, J., Yarbay Duman, T., Thompson, C. K., 2011. Time reference in agrammatic aphasia: A cross-linguistic study. J. Neurolinguist. 24, 652-673). With respect to reference to the (non-discourse-linked) future, data so far indicate that IWAs experience less difficulties as compared to past time reference (Bastiaanse, R., Bamyaci, E., Hsu, C., Lee, J., Yarbay Duman, T., Thompson, C. K., 2011. Time reference in agrammatic aphasia: A cross-linguistic study. J. Neurolinguist. 24, 652-673), supporting the assumptions of the PADILIH. Previous online studies of time reference in aphasia used methods such as reaction times analysis (e.g., Faroqi-Shah, Y., Dickey, M. W., 2009. On-line processing of tense and temporality in agrammatic aphasia. Brain Lang. 108, 97-111). So far, no such study used eye-tracking, even though this technique can bring additional insights (Burchert, F., Hanne, S., Vasishth, S., 2013. Sentence comprehension disorders in aphasia: the concept of chance performance revisited. Aphasiology 27, 112-125, doi:10.1080/02687038.2012.730603).

AIMS

This study investigated (1) whether processing of future and past time reference inflection differs between non-brain-damaged individuals (NBDs) and IWAs, and (2) underlying mechanisms of time reference comprehension failure by IWAs.

METHODS AND PROCEDURES

A visual-world experiment combining sentence-picture matching and eye-tracking was administered to 12 NBDs and 6 IWAs, all native speakers of German. Participants heard German sentences with periphrastic future ('will+V') or periphrastic past ('has+V-d') verb forms while they were presented with corresponding pictures on a computer screen.

RESULTS AND DISCUSSION

NBDs scored at ceiling and significantly higher than the IWAs. IWAs had below-ceiling performance on the future condition, and both participant groups were faster to respond to the past than to the future condition. These differences are attributed to a pre-existing preference to look at a past picture, which has to be overcome. Eye movement patterns suggest that both groups interpret future time reference similarly, while IWAs show a delay relative to NBDs in interpreting past time reference inflection. The eye tracking results support the PADILIH, because processing reference to the past in discourse syntax requires additional resources and thus, is problematic and delayed for people with aphasia.

Goal-oriented gaze strategies afforded by object interaction

Task influence has long been known to play a major role in the way our eyes scan a scene. Yet most studies focus either on visual search or on sequences of active tasks in complex real world scenarios. Few studies have contrasted the distribution of eye fixations during viewing and grasping objects. Here we address how attention is deployed when different actions are planned on objects, in contrast to when the same objects are categorized. In this respect, we are particularly interested in the role every fixation plays in the unfolding dynamics of action control. We conducted an eye-tracking experiment in which participants were shown images of real-world objects. Subjects were either to assign the displayed objects to one of two classes (categorization task), to mimic lifting (lifting task), or to mimic opening the object (opening task). Results suggest that even on simplified, two dimensional displays the eyes reveal the participant's intentions in an anticipatory fashion. For the active tasks, already the second saccade after stimulus onset was directed towards the central region between the two locations where the thumb and the rest of the fingers would be placed. An analysis of saliency at fixation locations showed that fixations in active tasks have higher correspondence with salient features than fixations in the passive task. We suggest that attention flexibly coordinates visual selection for information retrieval and motor planning, working as a gateway between three components, linking the task (action), the object (target), and the effector (hand) in an effective way.

A non-invasive head-holding device for chronic neural recordings in awake behaving monkeys

BACKGROUND

We have developed a novel head-holding device for behaving non-human primates that affords stability suitable for reliable chronic electrophysiological recording experiments. The device is completely non-invasive, and thus avoids the risk of infection and other complications that can occur with the use of conventional, surgically implanted head-fixation devices.

NEW METHOD

The device consists of a novel non-invasive head mold and bar clamp holder, and is customized to the shape of each monkey's head. The head-holding device that we introduce, combined with our recording system and reflection-based eye-tracking system, allows for chronic behavioral experiments and single-electrode or multi-electrode recording, as well as manipulation of brain activity.

RESULTS AND COMPARISON WITH EXISTING METHODS

With electrodes implanted chronically in multiple brain regions, we could record neural activity from cortical and subcortical structures with stability equal to that recorded with conventional head-post fixation. Consistent with the non-invasive nature of the device, we could record neural signals for more than two years with a single implant. Importantly, the monkeys were able to hold stable eye fixation positions while held by this device, demonstrating the possibility of analyzing eye movement data with only the gentle restraint imposed by the non-invasive head-holding device.

CONCLUSIONS

We show that the head-holding device introduced here can be extended to the head holding of smaller animals, and note that it could readily be adapted for magnetic resonance brain imaging over extended periods of time.

Cue strength in second-language processing: an eye-tracking study

This study used eye-tracking and grammaticality judgement measures to examine how second-language (L2) learners process syntactic violations in English. Participants were native Arabic and native Mandarin Chinese speakers studying English as an L2, and monolingual English-speaking controls. The violations involved incorrect word order and differed in two ways predicted to be important by the unified competition model [UCM; MacWhinney, B. (2005). A unified model of language acquisition. In J. F. Kroll & A. M. B. de Groot (Eds.), Handbook of bilingualism: Psycholinguistic approaches (pp. 49-67). Oxford: Oxford University Press.]. First, one violation had more and stronger cues to ungrammaticality than the other. Second, the grammaticality of these word orders varied in Arabic and Mandarin Chinese. Sensitivity to violations was relatively quick overall, across all groups. Sensitivity also was related to the number and strength of cues to ungrammaticality regardless of native language, which is consistent with the general principles of the UCM. However, there was little evidence of cross-language transfer effects in either eye movements or grammaticality judgements.

The role of attentional bias in the effect of food advertising on actual food intake among children

This study examined the potential moderating role of attentional bias (i.e., gaze duration, number of fixations, latency of initial fixation) in the effect of advergames promoting energy-dense snacks on children's snack intake. A randomized between-subject design was conducted with 92 children who played an advergame that promoted either energy-dense snacks or nonfood products. Eye movements and reaction times to food and nonfood cues were recorded to assess attentional bias during playtime using eye-tracking methods. Children could eat freely after playing the game. The results showed that playing an advergame containing food cues increased total intake. Furthermore, children with a higher gaze duration for the food cues ate more of the advertised snacks. In addition, children with a faster latency of initial fixation to the food cues ate more in total and ate more of the advertised snacks. The number of fixations on the food cues did not increase actual snack intake. Food advertisements are designed to grab attention, and this study shows that the extent to which a child's attention is directed to a food cue increases the effect of the advertisement.

Processing lexical ambiguity in sentential context: Eye-tracking data from brain-damaged and non-brain-damaged individuals

The purpose of the present study was to identify general and syndrome-specific deficits in the lexical processing of individuals with non-fluent and fluent aphasia compared to individuals without cognitive, neurological or language impairments. The time course of lexical access, as well as lexical selection and integration was studied using a visual-world paradigm in three groups of Russian speakers: 36 individuals in the control group, 15 individuals with non-fluent aphasia and eight individuals with fluent aphasia. Participants listened to temporarily ambiguous sentences wherein the context biased the interpretation of an ambiguous word toward one of its two meanings. In half of the experimental sentences, a reanalysis was needed upon encountering the disambiguating phrase. The effect of the length of the intervening material between the ambiguous word and the disambiguation point was additionally monitored. All groups of participants showed intact lexical access under slowed speech rate, but non-fluent participants experienced difficulties with timely activation of multiple referents. At later stages of lexical processing, they additionally demonstrated a specific impairment of reanalysis. The deficit in participants with fluent aphasia was not focalized at any specific stage of lexical processing. Rather, the breakdown of lexical processes in fluent aphasia was likely related to difficulties with the inhibition of irrelevant lexical activation, which is further supported by the finding that increased phonological distance between the ambiguous word and ambiguity resolution was influential to the offline performance in this group.

Recognition of facial emotions and identity in patients with mesial temporal lobe and idiopathic generalized epilepsy: an eye-tracking study

PURPOSE

To describe visual scanning pattern for facial identity recognition (FIR) and emotion recognition (FER) in patients with idiopathic generalized (IGE) and mesial temporal lobe epilepsy (MTLE). Secondary endpoint was to correlate the results with cognitive function.

METHODS

Benton Facial Recognition Test (BFRT) and Ekman&Friesen series were performed for FIR and FER respectively in 23 controls, 20 IGE and 19 MTLE patients. Eye movements were recorded by a Hi-Speed eye-tracker system. Neuropsychological tools explored cognitive function.

RESULTS

Correct FIR rate was 78% in controls, 70.7% in IGE and 67.4% (p=0.009) in MTLE patients. FER hits reached 82.7% in controls, 74.3% in IGE (p=0.006) and 73.4% in MTLE (p=0.002) groups. IGE patients failed in disgust (p=0.005) and MTLE ones in fear (p=0.009) and disgust (p=0.03). FER correlated with neuropsychological scores, particularly verbal fluency (r=0.542, p<0.001). Eye-tracking revealed that controls scanned faces more diffusely than IGE and MTLE patients for FIR, who tended to top facial areas. A longer scanning of the top facial area was found in the three groups for FER. Gap between top and bottom facial region fixation time decreased in MTLE patients, with more but shorter fixations in bottom facial region. However, none of these findings were statistically significant.

CONCLUSION

FIR was impaired in MTLE patients, and FER in both IGE and MTLE, particularly for fear and disgust. Although not statistically significant, those with impaired FER tended to perform more diffuse eye-tracking over the faces and have cognitive dysfunction.

Body region dissatisfaction predicts attention to body regions on other women

The proliferation of "idealized" (i.e., very thin and attractive) women in the media has contributed to increasing rates of body dissatisfaction among women. However, it remains relatively unknown how women attend to these images: does dissatisfaction predict greater or lesser attention to these body regions on others? Fifty healthy women (mean age=21.8 years) viewed images of idealized and plus-size models; an eye-tracker recorded visual attention. Participants also completed measures of satisfaction for specific body regions, which were then used as predictors of visual attention to these regions on models. Consistent with an avoidance-type process, lower levels of satisfaction with the two regions of greatest reported concern (mid, lower torso) predicted less attention to these regions; greater satisfaction predicted more attention to these regions. While this visual attention bias may aid in preserving self-esteem when viewing idealized others, it may preclude the opportunity for comparisons that could improve self-esteem.

Eye spy: the predictive value of fixation patterns in detecting subtle and extreme emotions from faces

Successful social interaction requires recognizing subtle changes in the mental states of others. Deficits in emotion recognition are found in several neurological and psychiatric illnesses, and are often marked by disturbances in gaze patterns to faces, typically interpreted as a failure to fixate on emotionally informative facial features. However, there has been very little research on how fixations inform emotion recognition in healthy people. Here, we asked whether fixations predicted detection of subtle and extreme emotions in faces. We used a simple model to predict emotion detection scores from participants' fixation patterns. The best fit of this model heavily weighted fixations to the eyes in detecting subtle fear, disgust and surprise, with less weight, or zero weight, given to mouth and nose fixations. However, this model could not successfully predict detection of subtle happiness, or extreme emotional expressions, with the exception of fear. These findings argue that detection of most subtle emotions is best served by fixations to the eyes, with some contribution from nose and mouth fixations. In contrast, detection of extreme emotions and subtle happiness appeared to be less dependent on fixation patterns. The results offer a new perspective on some puzzling dissociations in the neuropsychological literature, and a novel analytic approach for the study of eye gaze in social or emotional settings.

Reactivity to fearful expressions of familiar and unfamiliar people in children with autism: an eye-tracking pupillometry study

BACKGROUND

Individuals with autism are often reported to have difficulty with emotion processing. However, clinical and experimental data show that they are sensitive to familiarity; for example, they show normative attachment to familiar people, and have normative brain activity in response to familiar faces. To date, no study has measured their reactivity to the emotions of familiar vs. unfamiliar people. Thus, our aim was to determine whether individuals with autism would show normative reactivity to emotion in familiar people.

METHODS

Participants were 21 children with autism and 21 children with typical development, aged two to five years, matched on age and gender. The children observed videos of familiar people (their child-care teachers) and unfamiliar people expressing fear, whilst their visual attention and pupillary reactions were recorded (the latter as an index of emotional reactivity), using eye tracking technology.

RESULTS

The children with autism showed normative pupillary reactions (peak magnitude) to fear expressed by familiar people, but a reduced response to fear expressed by unfamiliar people. However, across familiarity conditions, the children with autism had longer latency peak responses than the typically developing children. This pattern of findings was independent of cognitive factors or visual attention as visual attention by group was not related to familiarity condition. The children with autism had reduced visual attention to neutral faces; however, on fearful faces there were no group differences. Abnormalities in pupillary reactivity in the autism group were related to less prosocial behaviour and more severe play and communication deficits.

CONCLUSIONS

Children with autism were less atypical in their responses to fearful expressions of people they know, arguing against a pervasive emotional impairment in autism, but rather one that may be mediated by familiarity.

Adaptive processing of fractions--evidence from eye-tracking

Recent evidence indicated that fraction pair type determined whether a particular fraction is processed holistically, componentially or in a hybrid manner. Going beyond previous studies, we investigated how participants adapt their processing of fractions not only to fraction type, but also to experimental context. To examine adaptation in fraction processing, we recorded participants' eye-fixation behaviour in a fraction magnitude comparison task. Participants' eye fixation behaviour indicated componential processing of fraction pairs with common components for which the decision-relevant components are easy to identify. Importantly, we observed that fraction processing was adapted to experimental context: Evidence for componential processing was stronger, when experimental context allowed valid expectations about which components are decision-relevant. Taken together, we conclude that fraction processing is adaptive beyond the comparison of different fraction types, because participants continuously adjust to the experimental context in which fractions are processed.

In the attraction, compromise, and similarity effects, alternatives are repeatedly compared in pairs on single dimensions

In multi-alternative choice, the attraction, compromise, and similarity effects demonstrate that the value of an alternative is not independent of the other alternatives in the choice-set. Rather, these effects suggest that a choice is reached through the comparison of alternatives. We investigated exactly how alternatives are compared against each other using eye-movement data. The results indicate that a series of comparisons is made in each choice, with a pair of alternatives compared on a single attribute dimension in each comparison. We conclude that psychological models of choice should be based on these single-attribute pairwise comparisons.

Early sensitivity for eyes within faces: a new neuronal account of holistic and featural processing

Eyes are central to face processing however their role in early face encoding as reflected by the N170 ERP component is unclear. Using eye tracking to enforce fixation on specific facial features, we found that the N170 was larger for fixation on the eyes compared to fixation on the forehead, nasion, nose or mouth, which all yielded similar amplitudes. This eye sensitivity was seen in both upright and inverted faces and was lost in eyeless faces, demonstrating it was due to the presence of eyes at fovea. Upright eyeless faces elicited largest N170 at nose fixation. Importantly, the N170 face inversion effect (FIE) was strongly attenuated in eyeless faces when fixation was on the eyes but was less attenuated for nose fixation and was normal when fixation was on the mouth. These results suggest the impact of eye removal on the N170 FIE is a function of the angular distance between the fixated feature and the eye location. We propose the Lateral Inhibition, Face Template and Eye Detector based (LIFTED) model which accounts for all the present N170 results including the FIE and its interaction with eye removal. Although eyes elicit the largest N170 response, reflecting the activity of an eye detector, the processing of upright faces is holistic and entails an inhibitory mechanism from neurons coding parafoveal information onto neurons coding foveal information. The LIFTED model provides a neuronal account of holistic and featural processing involved in upright and inverted faces and offers precise predictions for further testing.