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Facial appearance can be altered, not just by restyling but also by sensory processes. Exposure to a female face can, for instance, make subsequent faces look more masculine than they would otherwise. Two explanations exist. According to one, exposure to a female face renormalizes face perception, making that female and all other faces look more masculine as a consequence—a unidirectional effect. According to that explanation, exposure to a male face would have the opposite unidirectional effect. Another suggestion is that face gender is subject to contrastive aftereffects. These should make some faces look more masculine than the adaptor and other faces more feminine—a bidirectional effect. Here, we show that face gender aftereffects are bidirectional, as predicted by the latter hypothesis. Images of real faces rated as more and less masculine than adaptors at baseline tended to look even more and less masculine than adaptors post adaptation. This suggests that, rather than mental representations of all faces being recalibrated to better reflect the prevailing statistics of the environment, mental operations exaggerate differences between successive faces, and this can impact facial gender perception. [ABSTRACT FROM AUTHOR]

Illusory motion reversals (IMRs) can happen when looking at a repetitive pattern of motion, such as a spinning wheel. To date these have been attributed to either a form of motion aftereffect seen while viewing a moving stimulus or to the visual system taking discrete perceptual snapshots of continuous input. Here we present evidence that we argue is inconsistent with both proposals. First, we show that IMRs are driven by the adaptation of nondirectional temporal frequency tuned cells, which is inconsistent with the motion aftereffect account. Then we establish that the optimal frequency for inducing IMRs differs for color and luminance defined movement. These data are problematic for any account based on a constant rate of discrete perceptual sampling. Instead, we suggest IMRs result from a perceptual rivalry involving discrepant signals from a feature tracking analysis of movement and motion-energy based analyses. We do not assume that feature tracking relies on a discrete sampling of input at a fixed rate, but rather that feature tracking can (mis)match features at any rate less than a stimulus driven maximal resolution. Consistent with this proposal, we show that the critical frequency for inducing IMRs is dictated by the duty cycle of salient features within a moving pattern, rather than by the temporal frequency of luminance changes. [ABSTRACT FROM AUTHOR]

One of the oldest known visual aftereffects is the shape aftereffect, wherein looking at a particular shape can make subsequent shapes seem distorted in the opposite direction. After viewing a narrow ellipse, for example, a perfect circle can look like a broad ellipse. It is thought that shape aftereffects are determined by the dimensions of successive retinal images. However, perceived shape is invariant for large retinal image changes resulting from different viewing angles; current understanding suggests that shape aftereffects should not be impacted by the operations responsible for this viewpoint invariance. By viewing adaptors from an angle, with subsequent frontoparallel tests, we establish that shape aftereffects are not solely determined by the dimensions of successive retinal images. Moreover, by comparing performance with and without stereo surface slant cues, we show that shape aftereffects reflect a weighted function of retinal image shape and surface slant information, a hallmark of shape constancy operations. Thus our data establish that shape aftereffects can be influenced by perceived shape, as determined by constancy operations, and must therefore involve higher-level neural substrates than previously thought. [ABSTRACT FROM AUTHOR]

Determining if we, or another agent, were responsible for a sensory event can require an accurate sense of timing. Our sense of appropriate timing relationships must, however, be malleable as there is a variable delay between the physical timing of an event and when sensory signals concerning that event are encoded in the brain. One dramatic demonstration of such malleability involves having people repeatedly press a button thereby causing a beep. If a delay is inserted between button presses and beeps, when it is subsequently taken away beeps can seem to precede the button presses that caused them. For this to occur it is important that people feel they were responsible for instigating the beeps. In terms of their timing, as yet it is not clear what combination of events is important for motor-sensory temporal recalibration. Here, by introducing ballistic reaches of short or longer extent before a button press, we varied the delay between the intention to act and the sensory consequence of that action. This manipulation failed to modulate recalibration magnitude. By contrast, introducing a similarly lengthened delay between button presses and consequent beeps eliminated recalibration. Thus it would seem that the critical timing relationship for motor-sensory temporal recalibration is between tactile signals relating to the completion of an action and the subsequent auditory percept. [ABSTRACT FROM AUTHOR]

Abstract: After prolonged exposure to a female face, faces that had previously seemed androgynous are more likely to be judged as male. Similarly, after prolonged exposure to a face with expanded features, faces that had previously seemed normal are more likely to be judged as having contracted features. These facial aftereffects have both been attributed to the impact of adaptation upon a norm-based opponent code, akin to low-level analyses of colour. While a good deal of evidence is consistent with this, some recent data is contradictory, motivating a more rigorous test. In behaviourally matched tasks we compared the characteristics of aftereffects generated by adapting to colour, to expanded or contracted faces, and to male or female faces. In our experiments opponent coding predicted that the appearance of the adapting image should change and that adaptation should induce symmetrical shifts of two category boundaries. This combination of predictions was firmly supported for colour adaptation, somewhat supported for facial distortion aftereffects, but not supported for facial gender aftereffects. Interestingly, the two face aftereffects we tested generated discrepant patterns of response shifts. Our data suggest that superficially similar aftereffects can ensue from mechanisms that differ qualitatively, and therefore that not all high-level categorical face aftereffects can be attributed to a common coding strategy. [Copyright &y& Elsevier]

Observers change their audio-visual timing judgements after exposure to asynchronous audiovisual signals. The mechanism underlying this temporal recalibration is currently debated. Three broad explanations have been suggested. According to the first, the time it takes for sensory signals to propagate through the brain has changed. The second explanation suggests that decisional criteria used to interpret signal timing have changed, but not time perception itself. A final possibility is that a population of neurones collectively encode relative times, and that exposure to a repeated timing relationship alters the balance of responses in this population. Here, we simplified each of these explanations to its core features in order to produce three corresponding six-parameter models, which generate contrasting patterns of predictions about how simultaneity judgements should vary across four adaptation conditions: No adaptation, synchronous adaptation, and auditory leading/lagging adaptation. We tested model predictions by fitting data from all four conditions simultaneously, in order to assess which model/explanation best described the complete pattern of results. The latency-shift and criterion-change models were better able to explain results for our sample as a whole. The population-code model did, however, account for improved performance following adaptation to a synchronous adapter, and best described the results of a subset of observers who reported least instances of synchrony. [ABSTRACT FROM AUTHOR]

Cross-modal temporal recalibration describes a shift in the point of subjective simultaneity (PSS) between 2 events following repeated exposure to asynchronous cross-modal inputs--the adaptors. Previous research suggested that audiovisual recalibration is insensitive to the spatial relationship between the adaptors. Here we show that audiovisual recalibration can be driven by cross-modal spatial grouping. Twelve participants adapted to alternating trains of lights and tones. Spatial position was manipulated, with alternating sequences of a light then a tone, or a tone then a light, presented on either side of fixation (e.g., left tone--left light--right tone--right light, etc.). As the events were evenly spaced in time, in the absence of spatial-based grouping it would be unclear if tones were leading or lagging lights. However, any grouping of spatially colocalized cross-modal events would result in an unambiguous sense of temporal order. We found that adapting to these stimuli caused the PSS between subsequent lights and tones to shift toward the temporal relationship implied by spatial-based grouping. These data therefore show that temporal recalibration is facilitated by spatial grouping. [ABSTRACT FROM AUTHOR]

Deciding precisely when we have acted is challenging, as actions involve a train of neural events spread across both space and time. Repeated delays between actions and consequent events can result in a shift, such that immediate feedback can seem to precede the causative act. Here we examined which neurocognitive representations are affected during such sensorimotor temporal recalibration, by testing if the effect generalizes across limbs and whether it might reflect altered decision criteria for temporal judgments. Hand or foot adaptation phases were interspersed with simultaneity judgments about actions involving the same or opposite limb. Shifts in the distribution of participants' simultaneity responses were quantified using a detection-theoretic model, where a shift of both boundaries together gives a stronger indication that the effect is not simply a result of decision bias. By demonstrating that temporal recalibration occurs in the foot as well as the hand, we confirmed that it is a robust motor phenomenon: Both low and high boundaries shifted reliably in the same-limb conditions. However, in cross-limb conditions only the high boundary shifted reliably. These two patterns are interpreted to reflect a genuine change in how the time of action is represented, and a timing criterion shift, respectively. [ABSTRACT FROM AUTHOR]