Social Context and Rejection Expectations Modulate Neural and Behavioral Responses to Social Feedback.

When meeting other people, some are optimistic and expect to be accepted by others, whereas others are pessimistic and expect mostly rejections. How social feedback is evaluated in situations that meet or do not meet these biases and how people differ in their response to rejection and acceptance depending on the social situation are unknown. In this study, participants experienced rejection and acceptance by peers in two different social contexts, one with high (negative context) and the other with low probability of rejection (positive context). We examined how the neural and behavioral responses to rejection are altered by this context and whether it depends on the individual's sensitivity to rejection. Behavioral results show that, on average, people maintain an optimistic bias even when mostly experiencing rejection. Importantly, personality differences in rejection sensitivity affected both prior expectations to be rejected in the paradigm and the extent to which expectations changed during the paradigm. The context also strongly modulated ERPs and theta responses to rejection and acceptance feedback. Specifically, valence effects on neural responses were enhanced in the negative context, suggesting a greater relevance to monitor social feedback in such a situation. Moreover, midfrontal theta predicted how expectations were changed in response to prediction errors, stressing a role for theta in learning from social feedback. Surprisingly, interindividual differences in rejection sensitivity did not affect neural responses to feedback. Our results stress the importance of considering the interaction between subjective expectations and the social context for behavioral and neural responses to social rejection.

Effective connectivity underlying reward-based executive control.

Motivational influences on cognitive control play an important role in shaping human behavior. Cognitive facilitation through motivators such as prospective reward or punishment is thought to depend on regions from the dopaminergic mesocortical network, primarily the ventral tegmental area (VTA), inferior frontal junction (IFJ), and anterior cingulate cortex (ACC). However, how interactions between these regions relate to motivated control remains elusive. In the present functional magnetic resonance imaging study, we used dynamic causal modeling (DCM) to investigate effective connectivity between left IFJ, ACC, and VTA in a task-switching paradigm comprising three distinct motivational conditions (prospective monetary reward or punishment and a control condition). We found that while prospective punishment significantly facilitated switching between tasks on a behavioral level, interactions between IFJ, ACC, and VTA were characterized by modulations through prospective reward but not punishment. Our DCM results show that IFJ and VTA modulate ACC activity in parallel rather than by interaction to serve task demands in reward-based cognitive control. Our findings further demonstrate that prospective reward and punishment differentially affect neural control mechanisms to initiate decision-making.

Quantifying the individual auditory and visual brain response in 7-month-old infants watching a brief cartoon movie.

Electroencephalography (EEG) continues to be the most popular method to investigate cognitive brain mechanisms in young children and infants. Most infant studies rely on the well-established and easy-to-use event-related brain potential (ERP). As a severe disadvantage, ERP computation requires a large number of repetitions of items from the same stimulus-category, compromising both ERPs' reliability and their ecological validity in infant research. We here explore a way to investigate infant continuous EEG responses to an ongoing, engaging signal (i.e., "neural tracking") by using multivariate temporal response functions (mTRFs), an approach increasingly popular in adult EEG research. N = 52 infants watched a 5-min episode of an age-appropriate cartoon while the EEG signal was recorded. We estimated and validated forward encoding models of auditory-envelope and visual-motion features. We compared individual and group-based ('generic') models of the infant brain response to comparison data from N = 28 adults. The generic model yielded clearly defined response functions for both, the auditory and the motion regressor. Importantly, this response profile was present also on an individual level, albeit with lower precision of the estimate but above-chance predictive accuracy for the modelled individual brain responses. In sum, we demonstrate that mTRFs are a feasible way of analyzing continuous EEG responses in infants. We observe robust response estimates both across and within participants from only 5 min of recorded EEG signal. Our results open ways for incorporating more engaging and more ecologically valid stimulus materials when probing cognitive, perceptual, and affective processes in infants and young children.

Brain responses reveal that infants' face discrimination is guided by statistical learning from distributional information.

Infants' perception of faces becomes attuned to the environment during the first year of life. However, the mechanisms that underpin perceptual narrowing for faces are only poorly understood. Considering the developmental similarities seen in perceptual narrowing for faces and speech and the role that statistical learning has been shown to play for speech, the current study examined whether and how learning from distributional information impacts face identity discrimination. We familiarized 6.5-month-old infants with exemplars of female faces taken from a morphed continuum going from one identity to another. Using event-related brain potentials (ERPs), we show that only infants who were familiarized with a bimodal frequency distribution, but not infants familiarized with a unimodal frequency distribution, discriminated between identities. These results are the first to demonstrate the influence of probabilistic information on infants' face identity discrimination, suggesting that statistical learning contributes to perceptual attunement for both faces and language.

When in infancy does the "fear bias" develop?

Much research has focused on how infants respond to emotional facial expressions. One of the key findings in this area of research is that by 7months of age, but not younger, infants show a bias in processing fearful faces even when compared with other negative and novel facial expressions. A recent study by Heck and colleagues (Journal of Experimental Child Psychology, 2016, Vol. 147, pp. 100-110) challenges this idea by showing that 5-month-olds looked longer at fearful faces than at happy and at neutral faces when dynamic displays (videos) are used. Given that previous work failed to find enhanced attention to fearful faces in 5-month-olds using static displays (photographs), this was taken as evidence that biased attention to fear can be observed earlier when dynamic information is presented. However, we computed an analysis indicating that the overall amount of motion displayed in the videos in Heck and colleagues' study is confounded with emotion such that the greatest amount of motion is evident in the fearful face videos and may have driven infants' looking patterns. We discuss these findings and their limitations in the context of other research using dynamic emotion stimuli. Although these findings do not rule out the possibility that 5-month-olds are sensitive to fear, we stress the need to control for physical differences such as motion before any conclusions regarding the emergence of the fear bias during infancy can be drawn and in order to improve research practice in the field.

Unconscious discrimination of social cues from eye whites in infants.

Human eyes serve two key functions in face-to-face social interactions: they provide cues about a person's emotional state and attentional focus (gaze direction). Both functions critically rely on the morphologically unique human sclera and have been shown to operate even in the absence of conscious awareness in adults. However, it is not known whether the ability to respond to social cues from scleral information without conscious awareness exists early in human ontogeny and can therefore be considered a foundational feature of human social functioning. In the current study, we used event-related brain potentials (ERPs) to show that 7-mo-old infants discriminate between fearful and nonfearful eyes (experiment 1) and between direct and averted gaze (experiment 2), even when presented below the perceptual threshold. These effects were specific to the human sclera and not seen in response to polarity-inverted eyes. Our results suggest that early in ontogeny the human brain detects social cues from scleral information even in the absence of conscious awareness. The current findings support the view that the human eye with its prominent sclera serves critical communicative functions during human social interactions.

Neural and Behavioral Evidence for Infants' Sensitivity to the Trustworthiness of Faces.

Face evaluation is a key aspect of face processing in humans, serving important functions in regulating social interactions. Adults and preschool children readily evaluate faces with respect to a person's trustworthiness and dominance. However, it is unclear whether face evaluation is mainly a product of extensive learning or a foundational building block of face perception already during infancy. We examined infants' sensitivity to facial signs of trustworthiness (Experiment 1) and dominance (Experiment 2) by measuring ERPs and looking behavior in response to faces that varied with respect to the two facial attributes. Results revealed that 7-month-old infants are sensitive to facial signs of trustworthiness but not dominance. This sensitivity was reflected in infants' behavioral preference and in the modulation of brain responses previously linked to emotion detection from faces. These findings provide first evidence that processing faces with respect to trustworthiness has its origins in infancy and shed light on the behavioral and neural correlates of this early emerging sensitivity.

Aesthetic appreciation of poetry correlates with ease of processing in event-related potentials.

Rhetorical theory suggests that rhythmic and metrical features of language substantially contribute to persuading, moving, and pleasing an audience. A potential explanation of these effects is offered by "cognitive fluency theory," which stipulates that recurring patterns (e.g., meter) enhance perceptual fluency and can lead to greater aesthetic appreciation. In this article, we explore these two assertions by investigating the effects of meter and rhyme in the reception of poetry by means of event-related brain potentials (ERPs). Participants listened to four versions of lyrical stanzas that varied in terms of meter and rhyme, and rated the stanzas for rhythmicity and aesthetic liking. The behavioral and ERP results were in accord with enhanced liking and rhythmicity ratings for metered and rhyming stanzas. The metered and rhyming stanzas elicited smaller N400/P600 ERP responses than their nonmetered, nonrhyming, or nonmetered and nonrhyming counterparts. In addition, the N400 and P600 effects for the lyrical stanzas correlated with aesthetic liking effects (metered-nonmetered), implying that modulation of the N400 and P600 has a direct bearing on the aesthetic appreciation of lyrical stanzas. We suggest that these effects are indicative of perceptual-fluency-enhanced aesthetic liking, as postulated by cognitive fluency theory.

The developmental emergence of unconscious fear processing from eyes during infancy.

From early in life, emotion detection plays an important role during social interactions. Recently, 7-month-old infants have been shown to process facial signs of fear in others without conscious perception and solely on the basis of their eyes. However, it is not known whether unconscious fear processing from eyes is present before 7months of age or only emerges at around 7months. To investigate this question, we measured 5-month-old infants' event-related potentials (ERPs) in response to subliminally presented fearful and non-fearful eyes and compared these with 7-month-old infants' ERP responses from a previous study. Our ERP results revealed that only 7-month-olds, but not 5-month-olds, distinguished between fearful and non-fearful eyes. Specifically, 7-month-olds' processing of fearful eyes was reflected in early visual processes over occipital cortex and later attentional processes over frontal cortex. This suggests that, in line with prior work on the conscious detection of fearful faces, the brain processes associated with the unconscious processing of fearful eyes develop between 5 and 7months of age. More generally, these findings support the notion that emotion perception and the underlying brain processes undergo critical change during the first year of life. Therefore, the current data provide further evidence for viewing infancy as a formative period in human socioemotional functioning.

Neural tracking in infants - An analytical tool for multisensory social processing in development.

Humans are born into a social environment and from early on possess a range of abilities to detect and respond to social cues. In the past decade, there has been a rapidly increasing interest in investigating the neural responses underlying such early social processes under naturalistic conditions. However, the investigation of neural responses to continuous dynamic input poses the challenge of how to link neural responses back to continuous sensory input. In the present tutorial, we provide a step-by-step introduction to one approach to tackle this issue, namely the use of linear models to investigate neural tracking responses in electroencephalographic (EEG) data. While neural tracking has gained increasing popularity in adult cognitive neuroscience over the past decade, its application to infant EEG is still rare and comes with its own challenges. After introducing the concept of neural tracking, we discuss and compare the use of forward vs. backward models and individual vs. generic models using an example data set of infant EEG data. Each section comprises a theoretical introduction as well as a concrete example using MATLAB code. We argue that neural tracking provides a promising way to investigate early (social) processing in an ecologically valid setting.

Maternal odor reduces the neural response to fearful faces in human infants.

Maternal odor is known to play an important role in mother-infant-interaction in many altricial species such as rodents. However, we only know very little about its role in early human development. The present study therefore investigated the impact of maternal odor on infant brain responses to emotional expression. We recorded the electroencephalographic (EEG) signal of seven-month-old infants watching happy and fearful faces. Infants in two control groups exposed to no specific odor (control 1) or the odor of a different infant's mother (control 2) showed the expected EEG fear response. Crucially, this response was markedly absent in the experimental group exposed to their mother's odor. Thus, infants respond differently to fear signals in the presence of maternal odor. Our data therefore suggest that maternal odor can be a strong modulator of social perception in human infants.

Neural evidence for the impact of facial trustworthiness on object processing in a gaze-cueing task in 7-month-old infants.

Humans automatically judge a person's trustworthiness solely based on facial features and use these judgments to inform subsequent behavior. While recent studies demonstrate that already infants are sensitive to variance in facial trustworthiness, it remains unclear whether this variance also influences subsequent socio-cognitive processes. We investigated event-related brain responses (ERPs) to faces varying in trustworthiness in a gaze-cueing paradigm in 7-month-old infants. Our analysis focused on the ERP responses to cued or un-cued objects shown in isolation after the gaze-cue was presented. We observed an enhanced occipital positive slow wave (PSW) to un-cued compared to cued objects, suggesting a gaze-cueing effect irrespective of facial trustworthiness. Furthermore, objects in the un-cued condition elicited a larger fronto-central Nc when the gaze cue was provided by trustworthy compared to untrustworthy faces. This pattern suggests that while gaze cueing occurs irrespective of facial trustworthiness, allocation of attention, as indexed by modulation of the Nc amplitude, varies as a function of trustworthiness. Taken together, our results show that facial trustworthiness impacts object processing in the context of a gaze cueing paradigm, adding to the notion that it serves as an important social cue from early in ontogeny.

The developmental origins of subliminal face processing.

Sensitive responding to facial information is of key importance during human social interactions. Research shows that adults glean much information from another person's face without conscious perception, attesting to the robustness of face processing in the service of adaptive social functioning. Until recently, it was unclear whether such subliminal face processing is an outcome of extensive learning, resulting in adult face processing skills, or an early defining feature of human face processing. Here, we review recent research examining the early ontogeny and brain correlates of subliminal face processing, demonstrating that subliminal face processing: (1) emerges during the first year of life; (2) is multifaceted in response to transient (gaze, emotion) and stable (trustworthiness) facial cues; (3) systematically elicits frontal brain responses linked to attention allocation. The synthesized research suggests that subliminal face processing emerges early in human development and thus may play a foundational role during human social interactions. This offers a fresh look at the ontogenetic origins of unconscious face processing and informs theoretical accounts of human sociality.

Can processing of face trustworthiness bypass early visual cortex? A transcranial magnetic stimulation masking study.

As a highly social species, we constantly evaluate human faces to decide whether we can trust someone. Previous studies suggest that face trustworthiness can be processed unconsciously, but the underlying neural pathways remain unclear. Specifically, the question remains whether processing of face trustworthiness relies on early visual cortex (EVC), required for conscious perception. If processing of trustworthiness can bypass EVC, then disrupting EVC should impair subjective (conscious) trustworthiness perception while leaving objective (forced-choice) trustworthiness judgment intact. We applied double-pulse transcranial magnetic stimulation (TMS) to right EVC, at different stimulus onset asynchronies (SOAs) from presentation of a face in either the left or right hemifield. Faces were slightly rotated clockwise or counterclockwise, and were either trustworthy or untrustworthy. On each trial, participants discriminated 1) trustworthiness, 2) stimulus rotation, and 3) reported subjective visibility of trustworthiness. At early SOAs and specifically in the left hemifield, performance on the rotation task was impaired by TMS. Crucially, though TMS also impaired subjective visibility of trustworthiness, no effects on trustworthiness discrimination were obtained. Thus, conscious perception of face trustworthiness (captured by subjective visibility ratings) relies on intact EVC, while objective forced-choice trustworthiness judgments may not. These results are consistent with the hypothesis that objective trustworthiness processing can bypass EVC. For basic visual features, extrastriate pathways are well-established; but face trustworthiness depends on a complex configuration of features. Its potential processing without EVC is therefore of particular interest, further highlighting its ecological relevance.

Neural evidence for the subliminal processing of facial trustworthiness in infancy.

Face evaluation is thought to play a vital role in human social interactions. One prominent aspect is the evaluation of facial signs of trustworthiness, which has been shown to occur reliably, rapidly, and without conscious awareness in adults. Recent developmental work indicates that the sensitivity to facial trustworthiness has early ontogenetic origins as it can already be observed in infancy. However, it is unclear whether infants' sensitivity to facial signs of trustworthiness relies upon conscious processing of a face or, similar to adults, occurs also in response to subliminal faces. To investigate this question, we conducted an event-related brain potential (ERP) study, in which we presented 7-month-old infants with faces varying in trustworthiness. Facial stimuli were presented subliminally (below infants' face visibility threshold) for only 50ms and then masked by presenting a scrambled face image. Our data revealed that infants' ERP responses to subliminally presented faces differed as a function of trustworthiness. Specifically, untrustworthy faces elicited an enhanced negative slow wave (800-1000ms) at frontal and central electrodes. The current findings critically extend prior work by showing that, similar to adults, infants' neural detection of facial signs of trustworthiness occurs also in response to subliminal face. This supports the view that detecting facial trustworthiness is an early developing and automatic process in humans.

Boosting the effect of reward on cognitive control using TMS over the left IFJ.

Although an enhancing effect of reward on cognitive performance has been observed consistently, its neural underpinnings remain elusive. Recent evidence suggests that the inferior frontal junction (IFJ) may be a key player underlying such an enhancement by integrating motivational processes and cognitive control. However, its exact role and in particular a potential causality of IFJ activation is still unclear. In the present study, we therefore investigated the causal contributions of the left IFJ in motivated task switching by temporarily disrupting its activity using continuous theta burst stimulation (cTBS, Exp.1) or 1 Hz repetitive transcranial magnetic stimulation (rTMS, Exp.2). After TMS application over the left IFJ or a control site (vertex), participants performed a switch task in which numbers had to be judged by magnitude or parity. Different amounts of monetary rewards (high vs low) were used to manipulate the participants' motivational states. We measured reaction times and error rates. Irrespective of TMS stimulation, participants exhibited slower responses following task switches compared to task repeats. This effect was reduced in high reward trials. Importantly, we found that disrupting the IFJ improved participants' behavioral performance in the high reward condition. For high reward trials exclusively, error rates decreased when the IFJ was modulated with cTBS or 1 Hz rTMS but not after vertex stimulation. Our results suggest that the left IFJ is causally related to the increase in cognitive performance through reward.

Exploring the Role of Spatial Frequency Information during Neural Emotion Processing in Human Infants.

Enhanced attention to fear expressions in adults is primarily driven by information from low as opposed to high spatial frequencies contained in faces. However, little is known about the role of spatial frequency information in emotion processing during infancy. In the present study, we examined the role of low compared to high spatial frequencies in the processing of happy and fearful facial expressions by using filtered face stimuli and measuring event-related brain potentials (ERPs) in 7-month-old infants (N = 26). Our results revealed that infants' brains discriminated between emotional facial expressions containing high but not between expressions containing low spatial frequencies. Specifically, happy faces containing high spatial frequencies elicited a smaller Nc amplitude than fearful faces containing high spatial frequencies and happy and fearful faces containing low spatial frequencies. Our results demonstrate that already in infancy spatial frequency content influences the processing of facial emotions. Furthermore, we observed that fearful facial expressions elicited a comparable Nc response for high and low spatial frequencies, suggesting a robust detection of fearful faces irrespective of spatial frequency content, whereas the detection of happy facial expressions was contingent upon frequency content. In summary, these data provide new insights into the neural processing of facial emotions in early development by highlighting the differential role played by spatial frequencies in the detection of fear and happiness.

Putting the face in context: Body expressions impact facial emotion processing in human infants.

Body expressions exert strong contextual effects on facial emotion perception in adults. Specifically, conflicting body cues hamper the recognition of emotion from faces, as evident on both the behavioral and neural level. We examined the developmental origins of the neural processes involved in emotion perception across body and face in 8-month-old infants by measuring event-related brain potentials (ERPs). We primed infants with body postures (fearful, happy) that were followed by either congruent or incongruent facial expressions. Our results revealed that body expressions impact facial emotion processing and that incongruent body cues impair the neural discrimination of emotional facial expressions. Priming effects were associated with attentional and recognition memory processes, as reflected in a modulation of the Nc and Pc evoked at anterior electrodes. These findings demonstrate that 8-month-old infants possess neural mechanisms that allow for the integration of emotion across body and face, providing evidence for the early developmental emergence of context-sensitive facial emotion perception.

Pupillary responses reveal infants' discrimination of facial emotions independent of conscious perception.

Sensitive responding to others' emotions is essential during social interactions among humans. There is evidence for the existence of subcortically mediated emotion discrimination processes that occur independent of conscious perception in adults. However, only recently work has begun to examine the development of automatic emotion processing systems during infancy. In particular, it is unclear whether emotional expressions impact infants' autonomic nervous system regardless of conscious perception. We examined this question by measuring pupillary responses while subliminally and supraliminally presenting 7-month-old infants with happy and fearful faces. Our results show greater pupil dilation, indexing enhanced autonomic arousal, in response to happy compared to fearful faces regardless of conscious perception. Our findings suggest that, early in ontogeny, emotion discrimination occurs independent of conscious perception and is associated with differential autonomic responses. This provides evidence for the view that automatic emotion processing systems are an early-developing building block of human social functioning.