Of snakes and faces: An evolutionary perspective on the psychology of fear

Snakes and faces are unique stimuli because they are deeply grounded in evolutionarily shaped behavior systems. Snakes are the prototypical stimulus in a predatory defense system promoting escape from predators, which prepares primates for efficient processing, attentional priority, and rapid fear acquisition to snakes and other stimuli related to predation. The social submissiveness system plays a similar role on the social arena by promoting yielding to dominant individuals without jeopardizing the protection of the group. Supporting these theoretical propositions, empirical data from a research program spanning four decades demonstrate enhanced fear conditioning to snakes and threatening faces compared to neutral stimuli, as well as fast nonconscious processing of, and prioritized attention to, snakes and threatening faces. Human brain‐imaging data show that these effects are mediated by an extensive fear‐network centering on the amygdala.     

The narrow fellow in the grass: human infants associate snakes and fear

Why are snakes such a common target of fear? One current view is that snake fear is one of several innate fears that emerge spontaneously. Another is that humans have an evolved predisposition to learn to fear snakes. In the first study reported here, 9‐ to 10‐month‐old infants showed no differential spontaneous reaction to films of snakes versus other animals. In the second study, 7‐ to 18‐month‐old infants associated snakes with fear: As predicted, they looked longer at films of snakes while listening to a frightened human voice than while listening to a happy voice. In the third study, infants did not look differentially to still photos of snakes and other animals, indicating that movement is crucial to infants’ association of snakes with fear. These results offer support for the view that humans have a natural tendency to selectively associate snakes with fear.     

Recognition by association: Within‐ and cross‐modality associative priming with faces and voices

Recent literature has raised the suggestion that voice recognition runs in parallel to face recognition. As a result, a prediction can be made that voices should prime faces and faces should prime voices. A traditional associative priming paradigm was used in two studies to explore within‐modality priming and cross‐modality priming. In the within‐modality condition where both prime and target were faces, analysis indicated the expected associative priming effect: The familiarity decision to the second target celebrity was made more quickly if preceded by a semantically related prime celebrity, than if preceded by an unrelated prime celebrity. In the cross‐modality condition, where a voice prime preceded a face target, analysis indicated no associative priming when a 3‐s stimulus onset asynchrony (SOA) was used. However, when a relatively longer SOA was used, providing time for robust recognition of the prime, significant cross‐modality priming emerged. These data are explored within the context of a unified account of face and voice recognition, which recognizes weaker voice processing than face processing.     

Asymmetrical impact: vigilance for differences and self‐relevant stimuli

We hypothesized that people are ‘vigilant’ for differences between stimuli. In particular, we compared the reactions elicited by unexpected differences versus unexpected similarities. Participants imagined themselves in several situations where they learned something unexpected. This unexpected information showed either that two things previously thought to be similar were actually different or that two things previously thought to be different were actually similar. Also, the new information was either beneficial, neutral, or detrimental to the perceiver. Participants indicated for each situation how surprised they would be and how they would feel. Unexpected differences were rated as more surprising than unexpected similarities for positive and negative events, though not for neutral events. Participants also reported that beneficial differences would produce more positive affect than beneficial similarities, whereas detrimental differences would produce more negative affect than detrimental similarities. These findings support the asymmetrical impact hypothesis that differences have more psychological impact than similarities. Copyright © 2002 John Wiley & Sons, Ltd.     

When infants talk,infants listen: pre‐babbling infants prefer listening to speech with infant vocal properties

To learn to produce speech, infants must effectively monitor and assess their own speech output. Yet very little is known about how infants perceive speech produced by an infant, which has higher voice pitch and formant frequencies compared to adult or child speech. Here, we tested whether pre‐babbling infants (at 4–6 months) prefer listening to vowel sounds with infant vocal properties over vowel sounds with adult vocal properties. A listening preference favoring infant vowels may derive from their higher voice pitch, which has been shown to attract infant attention in infant‐directed speech (IDS). In addition, infants' nascent articulatory abilities may induce a bias favoring infant speech given that 4‐ to 6‐month‐olds are beginning to produce vowel sounds. We created infant and adult /i/ (‘ee’) vowels using a production‐based synthesizer that simulates the act of speaking in talkers at different ages and then tested infants across four experiments using a sequential preferential listening task. The findings provide the first evidence that infants preferentially attend to vowel sounds with infant voice pitch and/or formants over vowel sounds with no infant‐like vocal properties, supporting the view that infants' production abilities influence how they process infant speech. The findings with respect to voice pitch also reveal parallels between IDS and infant speech, raising new questions about the role of this speech register in infant development. Research exploring the underpinnings and impact of this perceptual bias can expand our understanding of infant language development.     

Loving and angry? Happy and sad? Understanding and reporting of mixed emotions in mother–child relationships by 6‐ to 12‐year‐olds

The Evaluative Space Model of emotions allows for the coactivation of positive‐appetitive and negative‐avoidant systems, but few studies have examined mixed emotions in child development. Existing research suggests children's understanding of opposite valence emotion combinations emerges by approximately 11 years of age. However, it is not yet clear whether various opposite valence combinations are understood at different ages, nor whether children can understand them in others before they have experienced such mixed emotions themselves. Semi‐structured interviews with 97 children investigated whether they regarded six combinations of opposite valence mixed emotions as possible, could provide reasons for them, and report their own experience of each in the context of mother–child relationships. Both understanding that such combinations are possible and ability to provide reasons for them increased after age 6 and up to age 11, but were still incomplete in 12‐year‐olds. Understanding of different opposite valence combinations developed at different rates. At each age, fewer children who showed understanding of these combinations in others reported having had a similar experience themselves. The findings suggest a need to systematically examine a range of mixed emotions in order to develop a comprehensive theory of the development of mixed emotion understanding. They also suggest extending research into adolescence.     

Linking actions and emotions: Evidence from 15‐ and 18‐month‐old infants

This study investigated 15‐ and 18‐month‐olds' understanding of the link between actions and emotions. Infants watched a videotape in which three adult models performed an action on an object. Each adult expressed the same emotion (positive, negative, or neutral affect) on completion of the action. Infants were subsequently given 20 seconds to interact with the object. Infants were less likely to perform the target action after the models' expressed negative as opposed to positive or neutral affect. Although infants' imitative behaviour was influenced by the models' emotional displays, this social referencing effect was not apparent in their more general object‐directed behaviour. For instance, infants in the negative emotion condition were just as quick to touch the object and spent the same amount of time touching the object as did infants in the neutral and positive emotion conditions. These findings suggest that infants understood that the models' negative affect was in response to the action, rather than the object itself. Infants apparently used this negative emotional information to appraise the action as one that was ‘undesirable’ or ‘bad’. Consequently, infants were now loath to reproduce the action themselves.     

Cause or effect: What matters? How 12‐month‐old infants learn to categorize artifacts

This paper investigates the role of cause and effect relations for infants' learning about artifacts. Two experiments tested whether 12‐month‐olds categorized a given set of unfamiliar artifacts according to overall similarity and/or according to part similarity, depending on what kind of video demonstration was presented before the start of the categorization task. In both experiments, the actions performed with objects were accompanied by interesting effects but the causal relation between object‐structure and effects was teased apart. In one video demonstration (Expt 1), the experimenter used the object part to produce some kind of effect in a causally plausible way. In another video demonstration (Expt 2), the experimenter performed similar actions with the same objects as in Expt 1, followed by the same effects as before. Importantly, however, no plausible cause–effect relation was provided this time. Only infants participating in Expt 1 categorized the set of unfamiliar objects according to part similarity. This finding suggests that 12‐month‐olds attend to the causal relation between specific object parts and their functional use when categorizing artifacts, rather than merely associating form‐characteristics with an interesting effect.     

Face detection in 2‐ to 6‐month‐old infants is influenced by gaze direction and species

Humans detect faces efficiently from a young age. Face detection is critical for infants to identify and learn from relevant social stimuli in their environments. Faces with eye contact are an especially salient stimulus, and attention to the eyes in infancy is linked to the emergence of later sociality. Despite the importance of both of these early social skills—attending to faces and attending to the eyes—surprisingly little is known about how they interact. We used eye tracking to explore whether eye contact influences infants' face detection. Longitudinally, we examined 2‐, 4‐, and 6‐month‐olds' (N = 65) visual scanning of complex image arrays with human and animal faces varying in eye contact and head orientation. Across all ages, infants displayed superior detection of faces with eye contact; however, this effect varied as a function of species and head orientation. Infants were more attentive to human than animal faces and were more sensitive to eye and head orientation for human faces compared to animal faces. Unexpectedly, human faces with both averted heads and eyes received the most attention. This pattern may reflect the early emergence of gaze following—the ability to look where another individual looks—which begins to develop around this age. Infants may be especially interested in averted gaze faces, providing early scaffolding for joint attention. This study represents the first investigation to document infants' attention patterns to faces systematically varying in their attentional states. Together, these findings suggest that infants develop early, specialized functional conspecific face detection.     

Maternal expectations about infant development of pre‐term and full‐term infants: a cross‐national comparison

In three European regions (The Netherlands, Northern Italy and Southern Italy) we investigated whether mothers of healthy pre‐term infants (n=92) adjust their expectations for the timing of developmental milestones in the first years of life as compared to mothers of full‐term infants (n=140). We examined whether these adjustments could be seen as reflecting a pessimistic view, as would be predicted from the ‘prematurity stereotype’ perspective. Partial corrections for prematurity were regularly made, but no indications were found for an overly pessimistic view. Moreover, the differences between the regions in the anticipated timing of mastery of milestones were larger than the effects of prematurity. Copyright © 2006 John Wiley & Sons, Ltd.     

The neural correlates of orienting to walking direction in 6‐month‐old infants: An ERP study

The ability to detect social signals represents a first step to enter our social world. Behavioral evidence has demonstrated that 6‐month‐old infants are able to orient their attention toward the position indicated by walking direction, showing faster orienting responses toward stimuli cued by the direction of motion than toward uncued stimuli. The present study investigated the neural mechanisms underpinning this attentional priming effect by using a spatial cueing paradigm and recording EEG (Geodesic System 128 channels) from 6‐month‐old infants. Infants were presented with a central point‐light walker followed by a single peripheral target. The target appeared randomly at a position either congruent or incongruent with the walking direction of the cue. We examined infants' target‐locked event‐related potential (ERP) responses and we used cortical source analysis to explore which brain regions gave rise to the ERP responses. The P1 component and saccade latencies toward the peripheral target were modulated by the congruency between the walking direction of the cue and the position of the target. Infants' saccade latencies were faster in response to targets appearing at congruent spatial locations. The P1 component was larger in response to congruent than to incongruent targets and a similar congruency effect was found with cortical source analysis in the parahippocampal gyrus and the anterior fusiform gyrus. Overall, these findings suggest that a type of biological motion like the one of a vertebrate walking on the legs can trigger covert orienting of attention in 6‐month‐old infants, enabling enhancement of neural activity related to visual processing of potentially relevant information as well as a facilitation of oculomotor responses to stimuli appearing at the attended location.     

Effects of testing on subsequent re‐encoding and long‐term forgetting of action‐relevant materials: On the influence of recall type

Testing one's memory of previously studied information reduces the rate of forgetting, compared to restudy. However, little is known about how this direct testing effect applies to action phrases (e.g., “wash the car”) – a learning material relevant to everyday memory. As action phrases consist of two different components, a verb (e.g., “wash”) and a noun (e.g., “car”), testing can either be implemented as noun‐cued recall of verbs or verb‐cued recall of nouns, which may differently affect later memory performance. In the present study, we investigated the effect of testing for these two recall types, using verbally encoded action phrases as learning materials. Results showed that repeated study–test practice, compared to repeated study–restudy practice, decreased the forgetting rate across 1 week to a similar degree for both noun‐cued and verb‐cued recall types. However, noun‐cued recall of verbs initiated more new subsequent learning during the first restudy, compared to verb‐cued recall of nouns. The study provides evidence that testing has benefits on both subsequent restudy and long‐term retention of action‐relevant materials, but that these benefits are differently expressed with testing via noun‐cued versus verb‐cued recall.     

Habituation in high‐risk infants: reliability and patterns of responding

We examined both the reliability of infant‐controlled habituation and patterns of responding in a group of high‐risk infants (mean age 16 mos). Good test–retest reliability was found for mean, total, and baseline looking time for one of the stimuli. Classification of infants' pattern of performance yielded two groups: linear (57%) and non‐linear (29%) responders; 14% of cases could not be classified because of cross‐session inconsistencies in performance. Linear responders had shorter total looking times, fewer trials to criterion, and showed more habituation than non‐linear responders, thus validating the linear/non‐linear distinction. Our findings indicate that the infant‐controlled habituation task can be used reliably with infants who are at high risk for developmental disorders. Indeed, we provide evidence that this task is not only reliable, but may also provide meaningful distinctions between infants within the high‐risk population. Discussion focuses on the role of attention in distinguishing between short (linear) and long (non‐linear) lookers. Copyright © 2003 John Wiley & Sons, Ltd.     

Lexical studies of Filipino person descriptors: adding personality‐relevant social and physical attributes

Lexical studies have focused on traits. In the Filipino language, we investigated whether additional dimensions can be identified when personality‐relevant terms for social roles, statuses and effects, plus physical attributes, are included. Filipino students (N = 496) rated themselves on 268 such terms, plus 253 markers of trait and evaluative dimensions. We identified 10 dimensions of social and physical attributes—Prominence, Uselessness, Attractiveness, Respectability, Uniqueness, Destructiveness, Presentableness, Strength, Dangerousness and Charisma. Most of these dimensions did not correspond in a one‐to‐one manner to Filipino or alternative trait models (Big Five, HEXACO, ML7). However, considerable redundancy was observed between the social and physical attribute dimensions and trait and evaluative dimensions. Thus, social and physical attributes communicate information about personality traits, and vice versa. Copyright © 2008 John Wiley & Sons, Ltd.     

Examining the relationships between self‐efficacy,task‐relevant attentional control,and task performance: Evidence from event‐related brain potentials

Self‐efficacy (SE) is a modifiable psychosocial factor related to individuals’ beliefs in their capabilities to successfully complete courses of action and has been shown to be positively associated with task performance. The authors hypothesized that one means through which SE is related with improved performance is through enhanced task‐relevant attentional control during task execution. To assess this hypothesis, we examined the relationships between SE and behavioural and neural indices of task performance and task‐relevant attentional control for 76 young adults during the completion of a flanker task. Results showed that greater SE was associated with greater response accuracy and P3b amplitude across task conditions, and faster RT under more difficult task conditions. Additionally, P3b amplitude was found to mediate the relationship between SE and task performance in the difficult condition. These findings suggest that greater attentional allocation to task‐relevant processes, including monitoring stimulus‐response relationships and focusing attention on working memory operations, may help explain the association between SE and improved task performance.     

`Babbling' and social context in infant monkeys: parallels to human infants

Although only humans use spoken language, the vocal communication of many animals shares some features with language. Within the context of their family, normal children and young non-human primates develop proficiency in the nuances of their species-specific vocal communication system. Engaging in speech-like phonetic activity, or babbling, occurs in all normal children regardless of their native language. Similar periods of vocal development have not been described previously for non-human primates. However, in the pygmy marmoset, a South American monkey, we found that the primary vocal behavior of infants parallels many characteristics of human infant babbling. These analogous features include universality, repetition, use of a subset of the adult vocal repertoire, recognizably adult-like vocal structure and lack of a clear vocal referent. Also, like human infants, young marmosets develop in a closely knit family unit that includes both parents and often older siblings. In this context, the babbling-like behavior of the marmoset infant stimulates interaction with caregivers, thereby serving a key role in the infant's own development. These developmental and social processes indicate that the study of vocal development in non-human primate species can provide insights into the function of babbling in humans.     

Habituation and novelty detection fNIRS brain responses in 5‐ and 8‐month‐old infants: The Gambia and UK

The first 1,000 days of life are a critical window of vulnerability to exposure to socioeconomic and health challenges (i.e. poverty/undernutrition). The Brain Imaging for Global Health (BRIGHT) project has been established to deliver longitudinal measures of brain development from 0 to 24 months in UK and Gambian infants and to assess the impact of early adversity. Here results from the Habituation‐Novelty Detection (HaND) functional near‐infrared spectroscopy (fNIRS) task at 5 and 8 months are presented (N = 62 UK; N = 115 Gambia). In the UK cohort distinct patterns of habituation and recovery of response to novelty are seen, becoming more robust from 5 to 8 months of age. In The Gambia, an attenuated habituation response is evident: a larger number of trials are required before the response sufficiently suppresses relative to the response during the first presented trials. Furthermore, recovery of response to novelty is not evident at 5 or 8 months of age. As this longitudinal study continues in The Gambia, the parallel collection of socioeconomic, caregiving, health and nutrition data will allow us to stratify how individual trajectories of habituation and recovery of response to novelty associate with different risk factors and adaptive mechanisms in greater depth. Given the increasing interest in the use of neuroimaging methods within global neurocognitive developmental studies, this study provides a novel cross‐culturally appropriate paradigm for the study of brain responses associated with attention and learning mechanisms across early development.