Face-like Stimuli Research Articles

Infant viewing of social scenes is under genetic control and is atypical in autism.

Long before infants reach, crawl, or walk, they explore the world by looking: they look to learn and to engage1, giving preferential attention to social stimuli including faces2, face-like stimuli3, and biological motion4. This capacity—social visual engagement—shapes typical infant development from birth5 and is pathognomonically impaired in children affected by autism6. Here we show that variation in viewing of social scenes—including levels of preferential attention and the timing, direction, and targeting of individual eye movements—is strongly influenced by genetic factors, with effects directly traceable to the active seeking of social information7. In a series of eye-tracking experiments conducted with 338 toddlers—including 166 epidemiologically-ascertained twins, 88 non-twins with autism, and 84 singleton controls—we find high monozygotic twin-twin concordance (0.91) and relatively low dizygotic concordance (0.35). Moreover, the measures that are most highly heritable, preferential attention to eye and mouth regions of the face, are also those that are differentially diminished in children with autism (Χ2=64.03, P<0.0001). These results—which implicate social visual engagement as a neurodevelopmental endophenotype—not only for autism, but for population-wide variation in social-information-seeking8—reveal a means of human biological niche construction, with phenotypic differences emerging from the interaction of individual genotypes with early life experience7.

The Human Fetus Preferentially Engages with Face-like Visual Stimuli

In the third trimester of pregnancy, the human fetus has the capacity to process perceptual information [1-3]. With advances in 4D ultrasound technology, detailed assessment of fetal behavior [4] is now possible. Furthermore, modeling of intrauterine conditions has indicated a substantially greater luminance within the uterus than previously thought [5]. Consequently, light conveying perceptual content could be projected through the uterine wall and perceived by the fetus, dependent on how light interfaces with maternal tissue. We do know that human infants at birth show a preference to engage with atop-heavy, face-like stimulus when contrasted with all other forms of stimuli [6, 7]. However, the viability of performing such an experiment based on visual stimuli projected through the uterine wall with fetalparticipants is not currently known. We examined fetal head turns to visually presented upright and inverted face-like stimuli. Here we show that the fetus in the third trimester of pregnancy is more likely to engage with upright configural stimuli when contrasted to inverted visual stimuli, in a manner similar to results with newborn participants. The current study suggests that postnatal experience is not required for this preference. In addition, we describe a new method whereby it is possible todeliver specific visual stimuli to the fetus. This new technique provides an important new pathway for the assessment of prenatal visual perceptual capacities.

Electrophysiological evidence for attentional capture by irrelevant angry facial expressions

Attention is believed to be biased toward threatening objects or faces. Therefore, we tested whether angry face stimuli would capture attention even when they are irrelevant to the task. Observers searched for a neutral face with a tilted nose. On some trials, the target was shown together with an irrelevant angry or happy face and we measured the N2pc (an electrophysiological marker of attentional selectivity) to the distractor expression. We found that angry distractors triggered an N2pc, whereas happy distractors did not. Follow-up experiments explored the reliability of the N2pc to angry distractors using upright or inverted angry faces, the eye or mouth region of angry faces and face-like stimuli. We conclude that a threatening expression has a high attentional priority due to its emotional content and captures attention despite being irrelevant for the task.

The N170 component is sensitive to face-like stimuli: a study of Chinese Peking opera makeup.

The N170 component is considered a neural marker of face-sensitive processing. In the present study, the face-sensitive N170 component of event-related potentials (ERPs) was investigated with a modified oddball paradigm using a natural face (the standard stimulus), human- and animal-like makeup stimuli, scrambled control images that mixed human- and animal-like makeup pieces, and a grey control image. Nineteen participants were instructed to respond within 1000ms by pressing the 'F' or 'J' key in response to the standard or deviant stimuli, respectively. We simultaneously recorded ERPs, response accuracy, and reaction times. The behavioral results showed that the main effect of stimulus type was significant for reaction time, whereas there were no significant differences in response accuracies among stimulus types. In relation to the ERPs, N170 amplitudes elicited by human-like makeup stimuli, animal-like makeup stimuli, scrambled control images, and a grey control image progressively decreased. A right hemisphere advantage was observed in the N170 amplitudes for human-like makeup stimuli, animal-like makeup stimuli, and scrambled control images but not for grey control image. These results indicate that the N170 component is sensitive to face-like stimuli and reflect configural processing in face recognition.

Face Detection and the Development of Own-Species Bias in Infant Macaques.

In visually complex environments, numerous items compete for attention. Infants may exhibit attentional efficiency-privileged detection, attention capture, and holding-for face-like stimuli. However, it remains unknown when these biases develop and what role, if any, experience plays in this emerging skill. Here, nursery-reared infant macaques' (Macaca mulatta; n=10) attention to faces in 10-item arrays of nonfaces was measured using eye tracking. With limited face experience, 3-week-old monkeys were more likely to detect faces and looked longer at faces compared to nonfaces, suggesting a robust face detection system. By 3months, after peer exposure, infants looked faster to conspecific faces but not heterospecific faces, suggesting an own-species bias in face attention capture, consistent with perceptual attunement.

Orienting Toward Face-Like Stimuli in Early Childhood.

Newborn infants orient preferentially toward face‐like or “protoface” stimuli and recent studies suggest similar reflexive orienting responses in adults. Little is known, however, about the operation of this mechanism in childhood. An attentional‐cueing procedure was therefore developed to investigate protoface orienting in early childhood. Consistent with the extant literature, 5‐ to 6‐year‐old children (n = 25) exhibited orienting toward face‐like stimuli; they responded faster when target location was cued by the appearance of a protoface stimulus than when location was cued by matched control patterns. The potential of this procedure to investigate the development of typical and atypical social perception is discussed.

Staring us in the face? An embodied theory of innate face preference

Human expertise in face perception grows over development, but even within minutes of birth, infants exhibit an extraordinary sensitivity to face-like stimuli. The dominant theory accounts for innate face detection by proposing that the neonate brain contains an innate face detection device, dubbed 'Conspec'. Newborn face preference has been promoted as some of the strongest evidence for innate knowledge, and forms a canonical stage for the modern form of the nature-nurture debate in psychology. Interpretation of newborn face preference results has concentrated on monocular stimulus properties, with little mention or focused investigation of potential binocular involvement. However, the question of whether and how newborns integrate the binocular visual streams bears directly on the generation of observable visual preferences. In this theoretical paper, we employ a synthetic approach utilizing robotic and computational models to draw together the threads of binocular integration and face preference in newborns, and demonstrate cases where the former may explain the latter. We suggest that a system-level view considering the binocular embodiment of newborn vision may offer a mutually satisfying resolution to some long-running arguments in the polarizing debate surrounding the existence and causal structure of newborns' 'innate knowledge' of faces.

Novelty preference in face perception by week-old lambs (Ovis aries)

An extensive literature has been accumulating, in recent years, on face-processing in sheep and on the relevance of faces for social interaction in this species. In spite of this, spontaneous preferences for face or non-face stimuli in lambs have not been reported. In this study we tested the spontaneous preference of 8-day-old lambs (N = 9) for three pairs of stimuli. In each pair, one stimulus was a face-like display, whereas the other presented the same inner features displaced in unnatural positions. One pair of stimuli was obtained from photographic images of ewes’ faces, the other two pairs were schematic face-like stimuli. Lambs could differentiate the two stimuli obtained by photos of conspecifics, looking longer at the non-face stimulus (p &lt; 0.05). We interpret this as a novelty preference, proving that few day-old lambs have already encoded the structural properties that define a face and recognize violations of those general properties.

Developmental changes in attention to faces and bodies in static and dynamic scenes.

Typically developing individuals show a strong visual preference for faces and face-like stimuli; however, this may come at the expense of attending to bodies or to other aspects of a scene. The primary goal of the present study was to provide additional insight into the development of attentional mechanisms that underlie perception of real people in naturalistic scenes. We examined the looking behaviors of typical children, adolescents, and young adults as they viewed static and dynamic scenes depicting one or more people. Overall, participants showed a bias to attend to faces more than on other parts of the scenes. Adding motion cues led to a reduction in the number, but an increase in the average duration of face fixations in single-character scenes. When multiple characters appeared in a scene, motion-related effects were attenuated and participants shifted their gaze from faces to bodies, or made off-screen glances. Children showed the largest effects related to the introduction of motion cues or additional characters, suggesting that they find dynamic faces difficult to process, and are especially prone to look away from faces when viewing complex social scenes—a strategy that could reduce the cognitive and the affective load imposed by having to divide one's attention between multiple faces. Our findings provide new insights into the typical development of social attention during natural scene viewing, and lay the foundation for future work examining gaze behaviors in typical and atypical development.

P1 and N170 components distinguish human-like and animal-like makeup stimuli

This study used event-related potentials to investigate the sensitivity of P1 and N170 components to human-like and animal-like makeup stimuli, which were derived from pictures of Peking opera characters. As predicted, human-like makeup stimuli elicited larger P1 and N170 amplitudes than did animal-like makeup stimuli. Interestingly, a right hemisphere advantage was observed for human-like but not for animal-like makeup stimuli. Dipole source analyses of 130-200-ms window showed that the bilateral fusiform face area may contribute to the differential sensitivity of the N170 component in response to human-like and animal-like makeup stimuli. The present study suggests that the amplitudes of both the P1 and the N170 are sensitive for the mouth component of face-like stimuli.

Effects of tilted orientations and face-like configurations on visual search asymmetry in macaques

Visual search asymmetry has been used as an important tool for exploring cognitive mechanisms in humans. Here, we examined visual search asymmetry in two macaques toward two types of stimulus: the orientation of line stimuli and face-like stimuli. In the experiment, the monkeys were required to detect an odd target among numerous uniform distracters. The monkeys detected a tilted-lines target among horizontal- or vertical-lined distracters significantly faster than a horizontal- or vertical-lined target among tilted-lined distracters, regardless of the display size. However, unlike the situation in which inverted-face stimuli were introduced as distracters, this effect was diminished if upright-face stimuli were used as distracters. Additionally, monkeys detected an upright-face target among inverted-face distracters significantly faster than an inverted-face target among upright-face distracters, regardless of the display size. These results demonstrate that macaques can search a target efficiently to detect both tilted lines among non-tilted lines and upright faces among inverted faces. This clarifies that there are several types of visual search asymmetry in macaques.

Sensitivity to First‐Order Relations of Facial Elements in Infant Rhesus Macaques

Faces are visually attractive to both human and nonhuman primates. Human neonates are thought to have a broad template for faces at birth and prefer face-like to non-face-like stimuli. To better compare developmental trajectories of face processing phylogenetically, here we investigated preferences for face-like stimuli in infant rhesus macaques using photographs of real faces. We presented infant macaques aged 15-25days with human, macaque, and abstract faces with both normal and linear arrangements of facial features, and measured infants' gaze durations, number of fixations, and latency to look to each face using eye-tracking technology. There was an overall preference for normal over linear facial arrangements for abstract and monkey faces, but not human faces. Moreover, infant macaques looked less at monkey faces than at abstract or human faces. These results suggest that species and facial configurations affect face processing in infant macaques, and we discuss potential explanations for these findings. Further, carefully controlled studies are required to ascertain whether infant macaques' face template can be considered as broad as human infants' face template.

Bartlett's schema theory: The unreplicated “portrait d'homme” series from 1932

In 1932, Frederic Bartlett laid the foundation for the later schema theory. His key assumption of previous knowledge affecting the processing of new stimuli was illustrated in the famous "portrait d'homme" series. Sequenced reproductions of ambiguous stimuli showed progressive object-likeness. As Bartlett pointed out, activation of specific schemata, for instance "the face schema", biases memory retrieval towards such schemata. In five experiments (Experiment 1, n = 53; Experiment 2, n = 177; Experiment 3, n = 36; Experiment 4, n = 6; Experiment 5, n = 2), we tested several factors potentially influencing retrieval biases-for example, by varying the general procedure of reproduction (repeated vs. serial) and by omitting versus providing visual or semantic cues for activating face schemata. Participants inspected face-like stimuli with the caption "portrait of the human" and reproduced them repeatedly under specific conditions. None of the experiments revealed a systematic tendency towards Bartlett's described case, even when the participants were explicitly instructed to draw "a face" like the previously inspected one. In one of the "serial reproduction" experiments, we even obtained contrary effects with decreasing face-likeness over the reproduction generations. A close analysis of the original findings raises questions about the replicability of Bartlett's findings, qualifying the "portrait d'homme" series more or less as an illustrative example of the main idea of reconstructive memory.

Quantifying Cognitive State From EEG Using Dependence Measures

The exquisite human ability to perceive facial features has been explained by the activity of neurons particularly responsive to faces, found in the fusiform gyrus and the anterior part of the superior temporal sulcus. This study hypothesizes and demonstrates that it is possible to automatically discriminate face processing from processing of a simple control stimulus based on processed EEGs in an online fashion with high temporal resolution using measures of statistical dependence applied on steady-state visual evoked potentials. Correlation, mutual information, and a novel measure of association, referred to as generalized measure of association (GMA), were applied on filtered current source density data. Dependences between channel locations were assessed for two separate conditions elicited by distinct pictures (a face and a Gabor grating) flickering at a rate of 17.5 Hz. Filter settings were chosen to minimize the distortion produced by bandpassing parameters on dependence estimation. Statistical analysis was performed for automated stimulus classification using the Kolmogorov-Smirnov test. Results show active regions in the occipito-parietal part of the brain for both conditions with a greater dependence between occipital and inferotemporal sites for the face stimulus. GMA achieved a higher performance in discriminating the two conditions. Because no additional face-like stimuli were examined, this study established a basic difference between one particular face and one nonface stimulus. Future work may use additional stimuli and experimental manipulations to determine the specificity of the current connectivity results.

Measuring Internal Representations from Behavioral and Brain Data

The study of internal knowledge representations is a cornerstone of the research agenda in the interdisciplinary study of cognition. An influential proposal assumes that the brain uses its internal knowledge of the external world to constrain, in a top-down manner, high-dimensional sensory data into a lower-dimensional representation that enables perceptual decisions and other higher-level cognitive functions [1-9]. This proposal relies on a precise formulation of the observer-specific internal knowledge (i.e., the internal representations, or models) that guides reduction of the high-dimensional retinal input onto a low-dimensional code. Here, we directly revealed the content of subjective internal representations by instructing five observers to detect a face in the presence of only white noise, to force a pure top-down, knowledge-based task. We used reverse correlation methods to visualize each observer's internal representation that supports detection of an illusory face. Using reverse correlation again, this time applied to observers' electroencephalogram activity, we established where and when in the brain specific internal knowledge conceptually interprets the input white noise as a face. We show that internal representations can be reconstructed experimentally from behavioral and brain data, and that their content drives neural activity first over frontal and then over occipitotemporal cortex.

Preverbal infants experience sound-shape correspondences

One of the most important crossmodal associations is between vision and sound, and we know that such bimodal information is of great importance in perceptual learning. Many crossmodal relationships are non-arbitrary or ‘natural’, and a particularly important case is object naming. While many object-name relationships are arbitrary, others are not. The clearest examples are known as onomatopoeia — the cuckoo and the kittiwake are named after the sounds they make. And a striking demonstration that such effects extend beyond onomatopoeic naming of familiar objects concerns shapes. When adults are shown two shapes, one angular and one with rounded contours, and given the words ‘Takete’ and ‘Maluma’ they will invariably associate ‘Takete’ with the angular shape, and ‘Maluma’ with the rounded shape. This effect was first described by Kohler in 1947, and there have been recent demonstrations of the effect with adults and young (3-year-old) children. Several researchers have suggested that these non-arbitrary associations may be of great importance in that they may influence and ‘bootstrap’ the infant’s early language development, particularly the learning of words for objects. If this is so, such associations should be present prior to language acquisition, and we describe three experiments which demonstrate such relationships in preverbal, 3–5-month-old infants, using random shapes, such as those in the figure, and angular and rounded face-like stimuli.

Inversion of contrast polarity abolishes spontaneous preferences for face-like stimuli in newborn chicks

A spontaneous preference for face-like stimuli has been demonstrated in domestic chicks, similar to that shown by human newborns, suggesting evolutionary continuity across species. Inversion of contrast polarity of face-like stimuli abolishes face preferences in human newborns. Here we investigated the effects of contrast polarity inversion and brain lateralization in chicks’ preferences for faces. In Experiment 1 face-naïve chicks were tested with a negative face obtained from a stimulus that elicited preferential approach in previous research. As in human newborns, reversal of contrast polarity abolished face-preferences. Experiments 2, 3 and 5 investigated the effect of adding a pupil-like dot within the inner features of the negative and of positive stimuli (a manipulation that re-established face-preference in human newborns). Chicks reacted to this by avoiding the face stimulus. In Experiments 4 and 6 we found that the preference expressed by chicks having only their left eye (right hemisphere) in use changed according to contrast polarity, whereas it remained unaffected in chicks having their right eye in use. Thus, in domestic chicks, as in human beings, a stimulus is perceived as face-like only if it presents the correct luminance pattern expected for a face under natural top-lit illumination and the right hemisphere seems to play a crucial role in this kind of social orienting responses.

Face-likeness and image variability drive responses in human face-selective ventral regions.

The human ventral visual stream contains regions that respond selectively to faces over objects. However, it is unknown whether responses in these regions correlate with how face-like stimuli appear. Here, we use parameterized face silhouettes to manipulate the perceived face-likeness of stimuli and measure responses in face- and object-selective ventral regions with high-resolution fMRI. We first use "concentric hyper-sphere" (CH) sampling to define face silhouettes at different distances from the prototype face. Observers rate the stimuli as progressively more face-like the closer they are to the prototype face. Paradoxically, responses in both face- and object-selective regions decrease as face-likeness ratings increase. Because CH sampling produces blocks of stimuli whose variability is negatively correlated with face-likeness, this effect may be driven by more adaptation during high face-likeness (low-variability) blocks than during low face-likeness (high-variability) blocks. We tested this hypothesis by measuring responses to matched-variability (MV) blocks of stimuli with similar face-likeness ratings as with CH sampling. Critically, under MV sampling, we find a face-specific effect: responses in face-selective regions gradually increase with perceived face-likeness, but responses in object-selective regions are unchanged. Our studies provide novel evidence that face-selective responses correlate with the perceived face-likeness of stimuli, but this effect is revealed only when image variability is controlled across conditions. Finally, our data show that variability is a powerful factor that drives responses across the ventral stream. This indicates that controlling variability across conditions should be a critical tool in future neuroimaging studies of face and object representation.

Perception of human face does not induce cooperation in darkness

Many studies showed that a concern to maintaining good reputation induces cooperation. Haley &amp; Fessler (2005) found that an illustration of a human face makes people cooperative in the dictator game. We demonstrate that this effect is moderated by a particular contextual variable – darkness. We found that the illustration of a human face did not increase an amount of donation in the dictator game when it was presented in a dark sound proof room. In darkness, an observer often has a hard time in monitoring an actor even when an actor can see an observer. Hence, we conjecture that the human face-like stimuli does not increase a concern to reputation when presented in darkness, because the risk of an observer to identify the actor is low. Current experimental results show a possibility that a system that makes people cooperative in response to cues indicating the presence of the others is triggered only in a specific condition.

Infant cognition

Infant cognition