People can represent temporal stimuli (e.g., pictures depicting past and future events) as spatially connoted dimensions arranged along the three main axes (horizontal, sagittal, and vertical). For example, past and future events are generally represented, from the perspective of the individuals, as being placed behind and in front of them, respectively. Here, we report that such a 3D representation can also emerge for facial stimuli of different ages. In three experiments, participants classified a central target face, representing an individual at different age stages, as younger or older than the reference face of 40 years. Manual responses were provided with two keys placed along the horizontal axis (Experiment 1), the sagittal axis (Experiment 2), and the vertical axis (Experiment 3). The results indicated that the younger faces were represented on the left/back/top side of the space, whereas the older faces were represented on the right/forward/bottom side of the space. Furthermore, in all experiments, the latencies decreased with the absolute difference between the age of the target face and that of the reference face (i.e., a distance effect). Overall, this work suggests that the spatial representation of time includes social features of the human face.

By the end of the first year of life, infants\' discrimination abilities tune to frequently experienced face groups. Little is known about the exploration strategies adopted to efficiently discriminate frequent, familiar face types. The present eye-tracking study examined the distribution of visual fixations produced by 10-month-old and 4-month-old singletons while learning adult (i.e., familiar) and child (i.e., unfamiliar) White faces. Infants were tested in an infant-controlled visual habituation task, in which post-habituation preference measured successful discrimination. Results confirmed earlier evidence that, without sibling experience, 10-month-olds discriminate only among adult faces. Analyses of gaze movements during habituation showed that infants\' fixations were centered in the upper part of the stimuli. The mouth was sampled longer in adult faces than in child faces, while the child eyes were sampled longer and more frequently than the adult eyes. At 10 months, but not at 4 months, global measures of scanning behavior on the whole face also varied according to face age, as the spatiotemporal distribution of scan paths showed larger within- and between-participants similarity for adult faces than for child faces. Results are discussed with reference to the perceptual narrowing literature, and the influence of age-appropriate developmental tasks on infants\' face processing abilities.

Knowing how humans differentiate children from adults has useful implications in many areas of both forensic and cognitive psychology. Yet, how we extract age from faces has been surprisingly underexplored in both disciplines. Here, we used a novel data-driven experimental technique to objectively measure the facial features human observers use to categorise child and adult faces. Relying on more than 35,000 trials, we used a reverse correlation technique that enabled us to reveal how specific features which are known to be important in face-perception - position, spatial-frequency (SF), and orientation - are associated with accurate child and adult discrimination. This showed that human observers relied on evidence in the nasal bone and eyebrow area for accurate adult categorisation, while they relied on the eye and jawline area to accurately categorise child faces. For orientation structure, only facial information of vertical orientation was linked to face-adult categorisation, while features of horizontal and, to a lesser extent oblique orientations, were more diagnostic of a child face. Finally, we found that SF diagnosticity showed a U-shaped pattern for face-age categorisation, with information in low and high SFs being diagnostic of child faces, and mid SFs being diagnostic of adult faces. Through this first characterisation of the facial features of face-age categorisation, we show that important information found in psychophysical studies of face-perception in general (i.e., the eye area, horizontals, and mid-level SFs) is crucial to the practical context of face-age categorisation, and present data-driven procedures through which face-age classification training could be implemented for real-world challenges.

Inattentional blindness (IB) refers to the nature of an individual being unaware of an unexpected stimulus when focusing on an attentional task. Investigation into IB provides an innovative approach for the research of attentional bias that is connected with an individual\'s immediate attentional capture. This study explored the effect of emotional valence and age of faces on the IB rates of children and adults. We employed a between-subject experimental design with a 2 (age of participants: child, adult) × 2 (age of face: child face, adult face) × 2 (emotional valence: positive, negative) method and used the classic IB task of cross judgment. The participants included 79 adults (54.63 ± 8.192 years old) and 78 children (10.62 ± 2.32 years old). The results showed that: (1) The IB rates of the two groups differed significantly. Children performed better than adults in detecting the faces appearing unexpectedly. (2) The effect of emotional valence only emerged on adult participants\' IB. Adults were significantly more likely to detect the positive-emotional faces than the negative-emotional ones. (3) The age of a face was not a significant factor to predict participants\' IB. Neither children nor adults showed a preference for the faces of a specific age (e.g., their own age). These findings revealed the distinct characteristics of attentional capture of children and adults when confronting unexpected facial stimuli.

Multiple facial cues such as facial expression and face gender simultaneously influence facial trustworthiness judgement in adults. The current work was to examine the effect of multiple facial cues on trustworthiness judgement across age groups. Eight-, 10-year-olds, and adults detect trustworthiness from happy and neutral adult faces (female and male faces) in Experiment 1. Experiment 2 included both adult and child faces wearing happy, angry, and neutral expressions. Nine-, 11-, 13-year-olds, and adults had to rate facial trustworthiness with a 7-point Likert scale. The results of Experiments 1 and 2 revealed that facial expression and face gender independently affected facial trustworthiness judgement in children aged 10 and below but simultaneously affected judgement in children aged 11 and above, adolescents, and adults. There was no own-age bias in children and adults. The results showed that children younger than 10 could not process multiple facial cues in the same manner as in older children and adults when judging trustworthiness. The current findings provide evidence for the stable-feature account, but not for the own-age bias account or the expertise account.

Face attractiveness can influence memory for previously seen faces. This effect has been shown to differ for young and older perceivers. Two parallel studies examined the moderation of both the age of the face and the age of the perceiver on the relationship between facial attractiveness and face memory. Study 1 comprised 29 young and 31 older participants; Study 2 comprised 25 young and 24 older participants. In both studies, participants completed an incidental face encoding and a surprise old/new recognition test with young and older faces that varied in face attractiveness. Face attractiveness affected memory for young but not older faces. In addition, young but not older perceivers showed a linear effect of facial attractiveness on memory for young faces, while both young and older perceivers showed a quadratic effect on memory for young faces. These findings extend previous work by demonstrating that the effect of facial attractiveness on face memory is a function of both the age of the perceiver and the age of the face. Factors that could account for such moderations of face and perceiver age on the associations between face attractiveness and face memory are discussed (e.g. age differences in social goals and face similarity/distinctiveness).

Adults\' face processing may be specialized for the dimensions of young adult faces. For example, young and older adults exhibit increased accuracy in normality judgments and greater agreement in attractiveness ratings for young versus older adult faces. The present study was designed to examine whether there is a similar young adult face bias in facial age estimates. In Experiment 1, we created a face age continuum by morphing an averaged young adult face with an averaged older adult face in 5% increments, for a total of 21 faces ranging from 0 to 100% old. Young and older adults estimated facial age for three stimulus age categories [young (morphs 0-30%), middle-aged (morphs 35-65%), and older adult (morphs 70-100%)]. Both age groups showed the least differentiation in age estimates for young adult faces, despite showing greater consensus across participants in estimates for young faces. In Experiment 2, young and older adults made age estimates for individual young and older adult identities. Both age groups were more accurate and showed greater consensus in age estimates for young faces. Collectively, these results provide evidence for a bias in processing young adult faces beyond that which is often observed in recognition and normality/attractiveness judgment tasks.

We examined category formation for faces differing in age in 9- and 12-month-olds, and the influence of exposure to infant faces on such ability. Infants were familiarized with adult or infant faces, and then tested with a novel exemplar from the familiarized category paired with a novel exemplar from a novel category (Experiment 1). Both age groups formed discrete categories of adult and infant faces, but exposure to infant faces in everyday life did not modulate performance. The same task was conducted with child versus infant faces (Experiment 2). Whereas 9-month-olds preferred infant faces after familiarization with child faces, but not child faces after familiarization with infant faces, 12-month-olds formed discrete categories of child and infant faces. Moreover, more exposure to infant faces correlated with higher novel category preference scores when infants were familiarized with infant faces in 12-month-olds, but not 9-month-olds. The 9-month-old asymmetry did not reflect spontaneous preference for infant over child faces (Experiment 3). These findings indicate that 9- and 12-month-olds can form age-based categories of faces. The ability of 12-month-olds to form separate child and infant categories suggests that they have a more exclusive representation of face age, one that may be influenced by prior experience with infant faces.

It is well-established that our recognition ability is enhanced for faces belonging to familiar categories, such as own-race faces and own-age faces. Recent evidence suggests that, for race, the recognition bias is also accompanied by different visual scanning strategies for own- compared to other-race faces. Here, we tested the hypothesis that these differences in visual scanning patterns extend also to the comparison between own and other-age faces and contribute to the own-age recognition advantage. Participants (young adults with limited experience with infants) were tested in an old/new recognition memory task where they encoded and subsequently recognized a series of adult and infant faces while their eye movements were recorded. Consistent with findings on the other-race bias, we found evidence of an own-age bias in recognition which was accompanied by differential scanning patterns, and consequently differential encoding strategies, for own-compared to other-age faces. Gaze patterns for own-age faces involved a more dynamic sampling of the internal features and longer viewing time on the eye region compared to the other regions of the face. This latter strategy was extensively employed during learning (vs. recognition) and was positively correlated to discriminability. These results suggest that deeply encoding the eye region is functional for recognition and that the own-age bias is evident not only in differential recognition performance, but also in the employment of different sampling strategies found to be effective for accurate recognition.

The correct interpretation of emotional expressions is crucial for social life. However, emotions in old relative to young faces are recognized less well. One reason for this may be decreased signal clarity of older faces due to morphological changes, such as wrinkles and folds, obscuring facial displays of emotions. Across three experiments, the present research investigates how misattributions of emotions to elderly faces impair emotion discrimination. In a preliminary task, neutral expressions were perceived as more expressive in old than in young faces by human raters (Experiment 1A) and an automatic system for emotion recognition (Experiment 1B). Consequently, task difficulty was higher for old faces relative to young faces in a visual search task (Experiment 2). Specifically, participants detected old faces expressing negative emotions less accurately and slower among neutral faces of their peers than young faces among neutral faces of their peers. Thus, we argue that age-related changes in facial features are the most plausible explanation for the differences in emotion perception between young and old faces. These findings are of relevance for the social interchange with the elderly, especially when multiple older individuals are present.