Developmental changes in the effect of inversion: using a picture book to investigate face recognition.

A novel child-oriented procedure was used to examine the face-recognition abilities of children as young as 2 years. A recognition task was embedded in a picture book containing a story about two boys and a witch. The story and the task were designed to be entertaining for children of a wide age range. In eight trials, the children were asked to pick out one of the boys from amongst eight distractors as quickly as possible. Response-time data to both upright and inverted conditions were analysed. The results revealed that children aged 6 years onwards showed the classic inversion effect. By contrast, the youngest children, aged 2 to 4 years, were faster at recognising the target face in the inverted condition than in the upright condition. Several possible explanations for this 'inverted inversion effect' are discussed.

Featural and configurational processes in the recognition of faces of different familiarity.

Previous research suggests that face recognition may involve both configurational and piecemeal (featural) processing. To explore the relationship between these processing modes, we examined the patterns of recognition impairment produced by blurring, inversion, and scrambling, both singly and in various combinations. Two tasks were used: recognition of unfamiliar faces (seen once before) and recognition of highly familiar faces (celebrities). The results provide further support for a configurational-featural distinction. Recognition performance remained well above chance if faces were blurred, scrambled, inverted, or simultaneously inverted and scrambled: each of these manipulations disrupts either configurational or piecemeal processing, leaving the other mode available as a route to recognition. However, blurred/scrambled and blurred/inverted faces were recognised at or near chance levels, presumably because both configurational processing and featural processing were disrupted. Similar patterns of effects were found for both familiar and unfamiliar faces, suggesting that the relationship between configurational and featural processing is qualitatively similar in both cases.

Evidence for holistic processing of faces viewed as photographic negatives.

Inversion and photographic negation both impair face recognition. Inversion seems to disrupt processing of the spatial relationship between facial features ('relational' processing) which normally occurs with upright faces and which facilitates their recognition. It remains unclear why negation affects recognition. To find out if negation impairs relational processing, we investigated whether negative faces are subject to the 'chimeric-face effect'. Recognition of the top half of a composite face (constructed from top and bottom halves of different faces) is difficult when the face is upright, but not when it is inverted. To perform this task successfully, the bottom half of the face has to be disregarded, but the relational processing which normally occurs with upright faces makes this difficult. Inversion reduces relational processing and thus facilitates performance on this particular task. In our experiments, subjects saw pairs of chimeric faces and had to decide whether or not the top halves were identical. On half the trials the two chimeras had identical tops; on the remaining trials the top halves were different. (The bottom halves were always different.) All permutations of orientation (upright or inverted) and luminance (normal or negative) were used. In experiment 1, each pair of 'identical' top halves were the same in all respects. Experiment 2 used differently oriented views of the same person, to preclude matches being based on incidental features of the images rather than the faces displayed within them. In both experiments, similar chimeric-face effects were obtained with both positive and negative faces, implying that negative faces evoke some form of relational processing. It is argued that there may be more than one kind of relational processing involved in face recognition: the 'chimeric-face effect' may reflect an initial 'holistic' processing which binds facial features into a 'Gestalt', rather than being a demonstration of the configurational processing involved in individual recognition.

The influence of feature-based information in the age processing of unfamiliar faces.

The influence of the internal features (eyes, nose, and mouth) in the age processing of unfamiliar faces was examined. Younger and older versions of the faces of six individuals (covering three different age ranges, from infancy to maturity) were used as donor stimuli. For each individual in turn, the effects on age estimates of placing older features in the younger face version (or vice versa) were investigated. Age estimates were heavily influenced by the age of the internal facial features. Experiment 2 replicated these effects with a larger number of faces within a narrower age range (after growth is complete and before major skin changes have occurred). Taken together, these two experiments show that the internal facial features may be influential in conveying age information to the perceiver. However, the mechanisms by which features exert their influence remain difficult to determine: although age estimates might be based on local information from the features themselves, an alternative possibility is that featural changes indirectly influence age estimates by altering the global three-dimensional shape of the head.

Recognising the ageing face: the role of age in face processing.

The effect of age-induced changes on face recognition were investigated as a means of exploring the role of age in the encoding of new facial memories. The ability of participants to recognise each of six previously learnt faces was tested with versions which were either identical to the learnt faces, the same age (but different in pose and expression), or younger or older in age. Participants were able to cope well with facial changes induced by ageing: their performance with older, but not younger, versions was comparable to that with faces which differed only in pose and expression. Since the large majority of different age versions were recognised successfully, it can be concluded that the process of recognition does not require an exact match in age characteristics between the stored representation of a face and the face currently in view. As the age-related changes explored here were those that occur during the period of growth, this in turn implies that the underlying structural physical properties of the face are (in addition to pose and facial expression) invariant to a certain extent.

Decay and interference effects in visuospatial short-term memory.

The method of constant stimuli was used to examine the accuracy with which two-dimensional spatial information can be represented in mental images. In experiment 1, subjects had to decide which of two successively presented two-dot separations was wider. Over the range of interstimulus intervals employed (0 to 30s), there was a linear relationship between interstimulus interval and spatial interval thresholds. In experiment 2 subjects' abilities to represent accurately more than one spatial interval at a time was investigated. Three dot pairs were presented, but only two pairs were to be compared, the third being completely irrelevant to the task. This manipulation doubled thresholds (relative to a two-dot-pair control condition), whether or not subjects were obliged to attend to the irrelevant dots. Overall, the results suggest that mental representations of spatial information may be temporally durable, but only in the absence of extraneous stimuli. The latter not only disrupt memory for spatial information, but appear to have obligatory access to it.

The influence of perceptual 'set' on the detection of motorcyclists using daytime headlights.

Voluntary daytime headlight use by the majority of motorcyclists might endanger those not using lights: it has been suggested that drivers might scan for lights rather than for motorcyclists per se. Two experiments are described that attempted to investigate this issue in the laboratory. Subjects had to decide as rapidly as possible whether or not a motorcyclist was present in each of a series of slides depicting traffic. Experiment 1 showed that headlight-using motorcyclists were more quickly detected than unlit motorcyclists, especially when they were far away. However, repeated exposure to headlight-using motorcyclists significantly delayed detection of an unlit motorcyclist. Experiment 2 showed that this delayed-detection effect occurred when only 60% of the motorcyclists shown were using their headlight. Under laboratory conditions, at least, subjects readily appear to develop a 'set' for responding on the basis of headlight-use, even when this is an unreliable guide to the motorcyclists' presence.

Factors influencing the accuracy of age estimates of unfamiliar faces.

Factors affecting the accuracy with which adults could assess the age of unfamiliar male faces aged between 5 and 70 years were examined. In the first experiment twenty-five 'young' adult subjects, aged 16-25, and twenty-five 'old' adults, aged 51-60, were used. Each subject saw five versions of three different faces: these consisted of an original version of each face and four manipulated versions of it. The manipulations consisted of mirror reversal, pseudo-cardioidal strain, thresholding, and elimination of all but the internal features of the face. The second experiment was similar except that a between-subjects design was used: each subject saw three faces for each age category of target face, but was exposed to only a single type of manipulation (plus a set of 'original' faces which were identical for all groups, so that the comparability of the different groups in age estimation could be checked). Results from both experiments were similar. Age estimates for unmanipulated 'original' faces were highly accurate, although subjects were most accurate with target faces that were within their own age range. Results for the manipulated faces implied that the importance of cardioidal strain as a necessary and sufficient cue to age may have been overestimated in previous reports: subjects' age estimates were accurate when cardioidal strain was absent from the stimulus, and poor when cardioidal strain was the only cue available.

Configurational factors in the perception of unfamiliar faces.

Young et al (1987) have demonstrated that the juxtaposition of top and bottom halves of different faces produces a powerful impression of a novel face. It is difficult to isolate perceptually either half of the 'new' face. Inversion of the stimulus, however, makes this task easier. Upright chimeric faces appear to evoke strong and automatic configurational processing mechanisms which interfere with selective piecemeal processing. In this paper three experiments are described in which a matching paradigm was used to show that Young et al's findings apply to unfamiliar as well as to familiar faces. The results highlight the way in which minor procedural differences may alter the way in which subjects perform face-recognition tasks.

Evidence for positional coding in hyperacuity.

Observers performed simple pattern discriminations [tests of orientation (vernier) acuity and spatial-interval acuity] with targets consisting of spatially separated squares. We investigated the effects on acuity of supernumerary squares placed at various mean positions between the two squares constituting the target configuration. The exact position of the supernumerary squares relative to the target squares changed randomly from trial to trial, so that their spatial relationship to the targets could not serve as a cue. Observers attempted to ignore these supernumerary squares and to base their judgments on the outer target squares alone. The supernumerary squares raised thresholds if they were sufficiently close (4.4-arcmin separation) to the target squares but not if they were at a greater distance (21.0 arcmin). The results therefore show that the observers could ignore the supernumerary squares, even when they fell into the space between the target squares. This finding suggests that observers can select a class of length- and orientation-tuned filter that is suited exactly to the requirements of a particular psychophysical task. We argue that filter models of hyperacuity are insufficient unless they address this critical issue of filter selection and that a complete model requires an explicit spatial representation of target feature position.

Biases and sensitivities in geometrical illusions.

Psychometric functions were collected to measure biases and sensitivities in certain classical illusory configurations, such as the Müller-Lyer. We found that sensitivities (thresholds or just noticeable differences) were generally not affected by the introduction of illusory biases, and the implications of this for theories of the illusions are discussed. Experiments on the Müller-Lyer figure showed that the effect depends upon mis-location of the ends of the figure, rather than upon a global expansion as demanded by the size-constancy theory. A new illusion is described in which the perceived position of a dot is displaced towards the centre of a surrounding cluster of dots, even though it is clearly discriminable from other members of the cluster by their colour. We argue that illusions illustrate powerful constraints upon visual processing: they arise when subjects are instructed to carry out a task to which the visual system is not adapted.

The role of social experience in the development of sexual competence in Rattus norvegicus.

To clarify the hitherto ambiguous role of pubertal social experience in determining adult sexual competence in male Rattus norvegicus , the quality of the subjects' social interactions was manipulated. In Experiment 1, subjects were raised from weaning onwards in male-only groups, in groups with limited periods of social deprivation at various ages, or in total isolation. Only the latter showed a significant degree of sexual impairment. In Experiment 2, subjects were raised in mixed-sex groups, in total physical (but not visual or olfactory) isolation from a surrounding mixed-sex group, or in physical isolation except for one hour's social contact per day with a peer. All of these subjects were sexually competent as adults. It thus appears that, in the laboratory rat, social deprivation must consist of total physical and visual and/or olfactory isolation in order to produce a significant degree of sexual impairment.