Search

We examined the influence of experience upon information-sampling and decision-making behaviour in a group of military personnel as they conducted risk assessments of scenes photographed from patrol routes during the recent conflict in Afghanistan. Their risk assessment was based on an evaluation of Potential Risk Indicators during examination of each scene. We found that both participant groups were equally likely to fixate Potential Risk Indicators, demonstrating similarity in the selectivity of their information-sampling. However, the inexperienced participants made more revisits to Potential Risk Indicators, had longer response times, and were more likely to decide that the scenes contained a high level of risk. Together, these results suggest that experience primarily modulates decision-making behaviour. We discuss potential routes to train personnel to conduct risk assessments in a more similar manner to experienced participants.

Recent studies have shown that the prevalence of target presentation in visual search has an impact on target detection rates, and also that searching for two targets leads to a decrement in performance (the “dual-target cost”). In the present experiments, we added to previous work that has examined the interaction between the prevalence effect and dual-target cost, and also to previous work that has examined a full range of prevalence levels. We found no interaction between the dual-target cost and prevalence effect, though the response criterion in dual-target search did interact with target prevalence in an unexpected manner. Furthermore, we detected anasymmetry in the prevalence effect: It was more marked for high than low prevalence. Implications for real-world tasks are discussed.

In two experiments we examined the perceived grouping of grids of equidistant dots, which are rapidly modulated over time so that alternate rows or columns are presented out of phase. In Experiment 1, we report that observers were able to group the grids consistent with the temporal modulation reliably, even at contrasts/frequencies for which flicker was not detectable. Moreover, flicker thresholds decreased with stimulus duration, whilst grouping thresholds did not change. In Experiment 2, we examined the impact of visual transients, by measuring performance when, either a mask or a contrast ramp was presented before and after the stimulus. Performance dropped substantially for both conditions, but remained significantly above chance. The results are discussed in relation to the role of temporal correlations in stimulus modulations and visual transients in grouping.

Seventeen adolescents with autism and seventeen typically developing children, matched for chronological age, were tested in a whole versus part paradigm in which participants matched a face target either to a complete face or to a face feature. Previous studies showed an accuracy advantage in whole‐face matching, indicating a holistic processing advantage for adults (Donnelly & Davidoff, 1999). It has been suggested that individuals with autism have difficulty in holistic processing, however the extent to which this difficulty may be moderated by attentional cues is uncertain. The present study included a condition that cued participants to the relevant face feature for matching. In the comparison group, the cue did not moderate the whole‐face matching advantage. In the participants with autism, cueing generated a whole‐face advantage, while uncued stimuli showed no difference between whole face and feature matching. This suggests that a lack of holistic processing in face processing, which is associated with individuals with autism, can be moderated with cueing. The implications for weak central coherence theory are discussed.

The present study reports the ability of young children to detect the Thatcher illusion. Participants were asked to detect the “unusual” face in a two-alternative forced-choice version of the Thatcher illusion with greyscale (Experiment 1) and monochrome “Mooney” face images (Experiment 2). The results of Experiment 1 showed that all groups of children could see the Thatcher illusion. When processing demands were increased (Experiment 2) sensitivity to the Thatcher task increased with age and was absent for 6-year-olds. The results are discussed in terms of differential task demands determining whether evidence for or against the development of configural face processing is found.

Three experiments were conducted to investigate the influence of fast temporally segmented presentations of alternate rows or columns on the perception of grids of either symmetrically or asymmetrically spaced dot-like stimuli. Experiments 1a and 1b demonstrated that observers were able to discriminate between temporally segmented presentations of rows/columns stimuli, but showed a reduced performance in discrimination between non-temporally segmented stimuli and temporally segmented stimuli that were spatially unstructured. Experiment 2 confirmed the influence of temporally segmented presentations of rows and columns using elements whose mean luminance summed to the same as the display background. Experiment 3 demonstrated that the influence of temporal cues reduced when display elements were asymmetrically spaced. The results are discussed in terms of the influence of external spatio-temporal factors on the neural mechanisms of visual grouping.

A series of visual search experiments explored whether early visual processes are sensitive to the overall shape of objects. Previous work (Wolfe & Bennett, 1997) has suggested that information concerning overall shape is not coded in early vision. However, in Experiment 1, we demonstrate that these previous findings are explicable in terms of non-target heterogeneity rather than an absence of shape information in early vision. In Experiments 2 and 3, we demonstrate that shape similarity, rather than individual contour similarity, can determine search efficiency. In Experiments 4 and 5, we show that manipulating the contrast polarity of contours and defining shape using texture significantly impeded search for an odd-one-out shape. The implications of these results for shape processing in early vision are discussed.

We explore the integration of facial features and house parts to form holistic representations of complete objects. In Experiments 1, 2, and 3, we test for evidence of the holistic representation of houses and faces. We do so by testing for a complete over part probe advantage (CPA) in 2AFC recognition and matching tasks. We present evidence consistent with holistic features being represented for both types of stimuli. In Experiments 4 and 5, we examine further theeffect with faces. Experiment 4 shows thatfacial features used in the matching task contribute differentially to CPAs across varying probe delays but with a similar pattern to that found in the recognition task (Experiment 1). Experiment5 shows thatCPAs are mandatory and cannot be removed by precueing with the probe type or the name of the feature to be probed.