Associate Professor Darren Burke

Identifying perceptual thresholds is critical for understanding the mechanisms that underlie signal evolution. Using computer-animated stimuli, we examined visual speed sensitivity in the Jacky dragon Amphibolurus muricatus, a species that makes extensive use of rapid motor patterns in social communication. First, focal lizards were tested in discrimination trials using random-dot kinematograms displaying combinations of speed, coherence, and direction. Second, we measured subject lizards' ability to predict the appearance of a secondary reinforcer (1 of 3 different computer-generated animations of invertebrates: cricket, spider, and mite) based on the direction of movement of a field of drifting dots by following a set of behavioural responses (e.g., orienting response, latency to respond) to our virtual stimuli. We found an effect of both speed and coherence, as well as an interaction between these 2 factors on the perception of moving stimuli. Overall, our results showed that Jacky dragons have acute sensitivity to high speeds. We then employed an optic flow analysis to match the performance to ecologically relevant motion. Our results suggest that the Jacky dragon visual system may have been shaped to detect fast motion. This pre-existing sensitivity may have constrained the evolution of conspecific displays. In contrast, Jacky dragons may have difficulty in detecting the movement of ambush predators, such as snakes and of some invertebrate prey. Our study also demonstrates the potential of the computeranimated stimuli technique for conducting nonintrusive tests to explore motion range and sensitivity in a visually mediated species.

© 2015 The Author(s). Previous research has demonstrated that while women prefer to look at the face of men regardless of relationship context, men preferentially look at women's bodies for short-term (over long-term) relationship judgments. The current study examined how self-rated mate value and 'mating intelligence' correlate with the subjective importance of information from the face or body. In addition, given the apparent sex differences in these judgments, we investigated whether either sex is aware of how the opposite-sex prioritizes this. Participants were 266 undergraduate students/volunteers who completed an online survey, measuring preferences for information from the face or body in short-term or long-term contexts, and a range of self-rated mate value measures. Information from the body was more important in short-term contexts for men (but not women), and correlated positively with mating strategy measures. While both sexes overestimated the opposite-sex's preference for looking at the body, women accurately perceived men's differential investment in face or body across contexts, whereas men assumed that women make decisions similarly to themselves. Women might benefit more than men from awareness of opposite-sex preferences as this could afford the enhancement or reduction of cues to sexual availability.

Almost all previous studies of face recognition have found that matching the same face depicted from different viewpoints incurs both reaction time and accuracy costs. This has been interpreted as evidence that the underlying neural representations of faces are viewpoint-specific, but such a conclusion depends on the experimental data being an accurate reflection of real-world viewpoint generalisation. An equally plausible explanation for poor viewpoint generalisation in experimental situations is that important information that is normally used to generalise across views in real-world settings is not available in the experiment. Stereoscopic information about the three-dimensional structure of the face is systematically misleading in nearly all previous investigations of face recognition, since a face depicted on a computer monitor contains explicit stereoscopic information that the face is flat. The current experiment demonstrates that viewpoint costs are reduced by depicting the face with stereoscopic three-dimensionality (compared to a synoptically presented face), raising the possibility that the viewpoint costs found in face recognition experiments might be a better reflection of the information that is typically unavailable in the experimental stimuli than of the underlying neural representation of facial identity. Crown Copyright © 2007.

In recent research the change-detection paradigm has been used along with cueing manipulations to show that more attention is allocated to the upper than lower facial region, and that this attentional allocation is disrupted by inversion. We report two experiments the object of which was to investigate how the type of information changed might be a factor in these findings by explicitly comparing the role of attention in detecting change to information thought to be 'special' to faces (second-order relations) with information that is more useful for basic-level object discrimination (first-order relations). Results suggest that attention is automatically directed to second-order relations in upright faces, but not first-order relations, and that this pattern of attentional allocation is similar across features. © 2007 a Pion publication.

The tendency of nectarivorous birds to perform better on tasks requiring them to avoid previously rewarding locations (to win-shift) than to return to them (win-stay) has been explained as an adaptation to the depleting nature of nectar. This interpretation relies on the previously untested assumption that the win-shift tendency is not associated with food types possessing a different distribution. To test this assumption, we examined the specificity of this bias to different food types in an omnivorous honeyeater, the noisy miner (Manorina melanocephala). As predicted, we found that the win-shift bias was sensitive to foraging context, manifesting only in association with foraging for nectar, not with foraging for invertebrates. © 2007 The Royal Society.

Although traditionally there has been a debate over whether object recognition involves 3-D structural descriptions or 2-D views, most current approaches to object recognition include the representation of object structure in some form. An advantage for the processing of structural or configural information in objects has been recently demonstrated using a change detection task (Keane, Hayward, & Burke, 2003). We report two experiments that extend this finding and show that configural information dominates change detection performance regardless of an object's orientation. Experiment 1 demonstrated the advantage that configural information has over shape and part arrangement information in change detection across four different object rotations in depth. Experiment 2 showed that this advantage occurs for both categorical and coordinate configural changes. These results are consistent with the hypothesis that configural information is a critical feature of object representations and that this information is utilized effectively in object recognition across changes in viewpoint. Copyright 2006 Psychonomic Society, Inc.

Prinzmetal and Beck (2001) Journal of Experimental Psychology: Human Perception and Performance 27 206-217) argued that a subset of visual illusions is caused by the same mechanisms that are responsible for the perception of vertical and horizontal - a theory they referred to as the tilt-constancy theory of visual illusions. They argued that these illusions should increase if the observer's head or head and body are tilted because extra reliance would then be placed on the illusion-inducing local visual context. Exactly that result had previously been reported in the case of the tilted-room and the rod-and-frame illusions. Prinzmetal and Beck reported similar increases in the tilt illusion (TI), as well as the Zöllner, Poggendorff, and Ponzo illusions. In two experiments, we re-examined the effect of head tilt on the TI. In experiment 1, we used more conventional TI stimuli, more standard experimental methods, and a more complete experimental design than Prinzmetal and Beck, and additionally extended the investigation to attraction as well as repulsion effects. Experiment 2 more closely replicated the Prinzmetal and Beck stimuli. Although we found that head tilt did increase TIs in both experiments, the increases were of the order of 1°-2°, more modest than the 7° reported by Prinzmetal and Beck. Significantly, the TI increase was larger when inducing tilts and head tilts were in the same direction than when they were in opposite directions, suggesting that the tilt-constancy theory may be oversimplified. In addition, because previous evidence renders unlikely the claim that the Poggendorff illusion can be explained simply in terms of misperceived orientation of the transversals, the question arises whether there might be some other explanation for the increase in the Zöllner, Poggendorff, and Ponzo illusions with body tilt that Prinzmetal and Beck reported.

Recent research suggests that there is an advantage for processing configural information in scenes and objects. The purpose of this study was to investigate the extent to which attention may account for this configural advantage. In Experiment 1, we found that cueing the location of change in single object displays improved detection performance for both configural and shape changes, yet cueing attention away from the location of change was detrimental only for shape change detection. A configural advantage was present for each cueing condition. Experiments 2A and 2B examined whether the configural advantage persisted in conditions where attention was distributed more widely, using a visual search paradigm. Although searches for configural changes were faster than those for shape changes across all set sizes, both types of information appeared to be processed with similar efficiency. Overall, these results suggest that the configural advantage is independent of the location or distribution of visual attention. © 2006 Psychology Press Ltd.

An issue of central concern in the object recognition literature is whether changes in the viewpoint from which an object is depicted produces systematic costs in performance, or whether perfomance is (largely) unaffected by such changes. This issue has generated a vigorous and lengthy debate because viewpoint-dependent or viewpoint-independent performance has been seen as a reflection of the underlying object representations. The current experiment shows that the effect of viewpoint differences between objects is strongly affected by whether or not they are depicted with stereoscopic depth, a result that is predicted by neither of the main approaches to object recognition. Instead, it is proposed that viewpoint costs in object recognition experiments are a function of the extent to which the information a subject is provided with generalizes across views, without this holding any necessary implications for the nature of the underlying object representations. © 2005 Psychology Press Ltd.

Studies have shown that nectar-feeding birds more easily learn to avoid a previously rewarding location (to win-shift) than to return to such a location (to win-stay). This pattern has been interpreted as evidence of an evolved adaptation to the fact that nectar is a depleting resource; however, such a conclusion requires ruling out the possibility that this tendency is a consequence of the experience of individual birds, and is more compelling if performance in the memory task reveals sensitivity to detailed features of the spatiotemporal distribution of nectar in the environment. We tested the tendency of captive-reared Regent honeyeaters, Xanthomyza phrygia, a species of nectar-feeding bird, to win-shift or win-stay at different intervisit intervals. The birds generally avoided rewarding locations after a short retention interval (10 min), but returned to these locations after a long retention interval (3 h). This behaviour tracks the replenishment rate of the flowers exploited by this species in the wild, even though the subjects were born and reared in captivity. © 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Palmisano et al (2000 Perception 29 57-67) found that adding coherent perspective jitter to constant-velocity radial flow improved visually induced illusions of self-motion (vection). This was a surprising finding, because unlike pure radial flow, this jittering radial flow should have generated sustained visual - vestibular conflicts - previously thought to always reduce/impair vection. We attempted to ascertain the essential stimulus features for this jitter advantage for vection by examining three novel types of jitter display. While adding incoherent jitter to radial flow was found to impair vection, adding coherent non-perspective jitter had little effect on this subjective experience (contrary to the notion that jitter improves vection by reducing adaptation to radial flow). Importantly, we found that coherent perspective jitter not only improves the vection induced by radial flow, but it also appears to induce modest vection by itself (demonstrating that vection can still occur when there is an extreme mismatch between actual and expected vestibular activity). These results suggest that the previously demonstrated advantage for coherent perspective jitter was due (in part at least) to jittering vection combining with forwards vection in depth to produce a more compelling overall vection experience.

In this study a change-detection paradigm is used to explore the nature of the information used to recognize three-dimensional, novel objects. In particular, whether we are sensitive to changes in part identity or configuration information. Experiments 1 and 2 showed that configural changes made to the object parts were significantly easier and quicker to detect than changes made to the shape or arrangement of object parts. Variance due to the total change in pixels did not predict performance in either of the experiments. The results of Experiment 3 showed the same pattern as Experiments 1 and 2, even though the objects used were altered to make part identity information more salient. Experiment 4 demonstrated that the physical size of the changes is not the crucial variable for this pattern of results. These findings are discussed in relation to the nature of visual representations and theories of object recognition.

The parallel drawn by Norman between the dorsal and ventral systems and direct and indirect approaches is based on two misrepresentations of the direct approach - that it is concerned only with the unconscious control of action, and that it cannot explain learning. We propose a way of understanding the visual system differences from within the direct approach.

Numerous previous investigators have explained species differences in spatial memory performance in terms of differences in foraging ecology. In three experiments we attempted to extend these findings by examining the extent to which the spatial memory performance of echidnas ¿or "spiny anteaters"¿ can be understood in terms of the spatio-temporal distribution of their prey ¿ants and termites¿. This is a species and a foraging situation that have not been examined in this way before. Echidnas were better able to learn to avoid a previously rewarding location ¿to "win-shift"¿ than to learn to return to a previously rewarding location ¿to "win-stay"¿, at short retention intervals, but were unable to learn either of these strategies at retention intervals of 90 min. The short retention interval results support the ecological hypothesis, but the long retention interval results do not.

Implicit learning tasks usually involve the learning of complex rules. While this does reduce the likelihood of subjects becoming aware of the relationship to be learned, it also raises the possibility of explaining improved performance in terms of explicit processes. The current experiments are an attempt to develop a task which shows evidence of implicit learning, but which involves the learning of a very simple rule and so avoids these alternative explanations. In two experiments, we exposed subjects to learning trials in which a target letter (or shape) was immediately preceded by a cue letter (or shape) in otherwise random nine-letter (or 15-shape) sequences. In a test phase, subjects responded more quickly to cued than uncued targets if the learning phase had involved reliable cue-target pairings, but not following random control pairings. This was true of subjects who were classified as aware and those classified as unaware of the cue-target relationship. © 2000 Academic Press.

Liu, Tyler, and Schor (1992 Vision Research 32 1471-1479) reported the surprising finding that dichoptically presented orthogonal sine-wave gratings do not always produce binocular rivalry. Gratings of high spatial frequency, and especially of low contrast, fuse to produce a stable percept of a dichoptic plaid. Using a somewhat different perceptual task, we replicated those findings and extended them. The probability of a plaid percept is higher for square-wave gratings than for sine-wave gratings, and higher still for rectangular-wave gratings with high duty cycles (with very thin light or dark bars). Experiments were conducted to test whether this duty-cycle effect was due to changes in overall luminance, or in the size of the regions of luminance congruity (which may reduce the probability of rivalry), but no such effects could account for the results. The presence of locally conflicting contour information in the two eyes was shown to be an important determinant of rivalry onset, but, since removing such regions did not eliminate rivalry, other factors also have a role to play. The spatial frequency composition of the gratings is one such factor which is consistent with all of the findings we report.