Decay and interference effects in visuospatial short-term memory

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The effect of familiarity on face adaptation

Face aftereffects can provide information on how faces are stored by the human visual system (eg Leopold et al, 2001 Nature Neuroscience 4 89 – 94), but few studies have used robustly represented (highly familiar) faces. In this study we investigated the influence of facial familiarity on adaptation effects. Participants were adapted to a series of distorted faces (their own face, a famous face, or an unfamiliar face). In experiment 1, figural aftereffects were significantly smaller when participants were adapted to their own face than when they were adapted to the other faces (ie their own face appeared significantly less distorted than a famous or unfamiliar face). Experiment 2 showed that this ‘own-face’ effect did not occur when the same faces were used as adaptation stimuli for participants who were unfamiliar with them. Experiment 3 replicated experiment 1, but included a pre-adaptation baseline. The results highlight the importance of considering facial familiarity when conducting research on face aftereffects

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 effects 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

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

Longitudinal studies of play in <italic>Rattus norvegicus</italic>

This thesis describes experiments and observational studies of social play in Rattus norvegicus. focussing on two aspects of play which have received relatively little attention: the relationship of play to other behaviours during development, and the immediate causation of play, Chapter two looks at play in relation to other social and non-social behaviours. Social play showed a distinctive inverted "U"-shaped ontogenetic trend (as did exploration), and was the major form of social interaction for young rats. However, social behaviours accounted for little of the developing animal's overall time-budget. No evidence was found for a relationship between play and the agonistic behaviours it is traditionally supposed to resemble. Experiments two and three provide further data on this point. Chapter three looks at temporal and contextual aspects of play—features which have been studied very little. Most play-bouts were found to be very short, and to show little reciprocity between interactants. Play occurred in a context of exploration, play, and activity, and was not associated with sedentary or agonistic behaviours. Experiments on play's immediate causation highlight the importance of environmental factors in determining whether play will occur. Experiment one shows that the "rebound" effect (increased play induced by prior short-term social deprivation) is not ameliorated by non-playful social contact. Experiment two looks at the effects on play of environmental change. Experiment three shows that food-deprivation selectively suppresses play. These results suggest that play's "costs" may have been overestimated; that play may have immediate benefits (exercise and allo-grooming); and that of the plethora of benefits which play could provide for this particular species, practice of agonistic activities seems the least plausible

Effect of vertical stretching on the extraction of mean identity from faces

Observers can extract the mean identity from a set of faces and falsely recognise it as a genuine set member. The current experiment demonstrated that this ‘perceptual averaging’ also occurs with vertically stretched faces. On each trial, participants decided whether a target face was present in a preceding set of four faces. In the control condition, the faces were all normally proportioned; in the stretched set condition, the face sets were stretched but the targets were normal; and in the stretched target condition, the face sets were normal but the targets were stretched. In all three conditions, participants falsely identified the set mean as a face that had been presented within the set, implying that this identity-averaging effect is based on high-level identity information rather than the low-level physical characteristics of the face stimuli

Can Social Categorisation Elicit Own-Group Biases in Face Recognition

Previous research has demonstrated a number of own-group biases in face recognition. For example, people are better at recognising own-race compared to other-race faces (Meissner & Brigham, 2001); and own-age compared to other-age faces (Anastasi & Rhodes, 2012). However, exactly why these own-group biases occur is unclear. Perceptual expertise and social-cognitive accounts have been put forward in an attempt to explain these effects. The first suggests the own-group advantage arises from the relatively increased experience (and therefore expertise) we have differentiating own-group faces; while the second suggests these effects are simply the result of categorising a face as belonging to our ‘in’ or ‘out’ group. Two studies explored whether own-group biases can be brought about by mere categorisation at encoding. Participants were shown 40 facial images grouped according to in-/out-group status. Study One used University membership as the grouping variable; while Study Two grouped faces (and participants) according to their position on Brexit (i.e. as Leave or Remain supporters). Differences in accuracy for in- and out-group faces were investigated, alongside the influence of in-group affiliation strength. Results are discussed in terms of the perceptual expertise and social-cognitive explanations of own-group biases

Comparison of methods for numerical calculation of continuum damping

Continuum resonance damping is an important factor in determining the stability of certain global modes in fusion plasmas. A number of analytic and numerical approaches have been developed to compute this damping, particularly in the case of the toroidicity-induced shear Alfv\'en eigenmode. This paper compares results obtained using an analytical perturbative approach with those found using resistive and complex contour numerical approaches. It is found that the perturbative method does not provide accurate agreement with reliable numerical methods for the range of parameters examined. This discrepancy exists even in the limit where damping approaches zero. When the perturbative technique is implemented using a standard finite element method, the damping estimate fails to converge with radial grid resolution. The finite elements used cannot accurately represent the eigenmode in the region of the continuum resonance, regardless of the number of radial grid points used.Comment: 19 pages, 9 figure

Facial aesthetics: babies prefer attractiveness to symmetry

The visual preferences of human infants for faces that varied in their attractiveness and in their symmetry about the midline were explored. The aim was to establish whether infants' visual preference for attractive faces may be mediated by the vertical symmetry of the face. Chimeric faces, made from photographs of attractive and unattractive female faces, were produced by computer graphics. Babies looked longer at normal and at chimeric attractive faces than at normal and at chimeric unattractive faces. There were no developmental differences between the younger and older infants: all preferred to look at the attractive faces. Infants as young as 4 months showed similarity with adults in the 'aesthetic perception' of attractiveness and this preference was not based on the vertical symmetry of the face