Race-specific perceptual discrimination improvement following short individuation training with faces

This study explores the effect of individuation training on the acquisition of race-specific expertise. First, we investigated whether practice individuating other-race faces yields improvement in perceptual discrimination for novel faces of that race. Second, we asked whether there was similar improvement for novel faces of a different race for which participants received equal practice, but in an orthogonal task that did not require individuation. Caucasian participants were trained to individuate faces of one race (African American or Hispanic) and to make difficult eye-luminance judgments on faces of the other race. By equating these tasks we are able to rule out raw experience, visual attention, or performance/success-induced positivity as the critical factors that produce race-specific improvements. These results indicate that individuation practice is one mechanism through which cognitive, perceptual, and/or social processes promote growth of the own-race face recognition advantage.     

Contrasting rule-based and similarity-based category learning: The effects of mood and prior knowledge on ambiguous categorization

This study adopts a dual-system view of category learning. The findings suggest that consumers who learn a dominant feature as a verbal rule for a product category will classify a new ambiguous product according to that feature even if it more closely resembles a different product category. The findings also demonstrate that dominant features can bias categorization toward a less prototypical category in the event that the new product breaks the rule. We refer to this phenomenon as criterial inferencing. Lastly, we offer unique empirical evidence to suggest that mood influences category learning and thus attenuates the criterial inferencing bias.     

Towards mouse models of perseveration: a heritable component in extinction of operant behavior in fourteen standard and recombinant inbred mouse lines

Extinction of instrumental responses is an essential skill for adaptive behavior such as foraging. So far, only few studies have focused on extinction following appetitive conditioning in mice. We studied extinction of appetitive operant lever-press behavior in six standard inbred mouse strains (A/J, C3H/HeJ, C57BL/6J, DBA/2J, BALB/cByJ and NOD/Ltj) and eight recombinant inbred mouse lines. From the response rates at the end of operant and extinction training we computed an extinction index, with higher values indicating better capability to omit behavioral responding in absence of reward. This index varied highly across the mouse lines tested, and the variability was partially due to a significant heritable component of 12.6%.To further characterize the relationship between operant learning and extinction, we calculated the slope of the time course of extinction across sessions. While many strains showed a considerable capacity to omit responding when lever pressing was no longer rewarded, we found a few lines showing an abnormally high perseveration in lever press behavior, showing no decay in response scores over extinction sessions.No correlation was found between operant and extinction response scores, suggesting that appetitive operant learning and extinction learning are dissociable, a finding in line with previous studies indicating that these forms of learning are dependent on different brain areas. These data shed light on the heritable basis of extinction learning and may help develop animal models of addictive habits and other perseverative disorders, such as compulsive food seeking and eating.     

The role of variation in the perception of accented speech

Phonetic variation has been considered a barrier that listeners must overcome in speech perception, but has been proved beneficial in category learning. In this paper, I show that listeners use within-speaker variation to accommodate gross categorical variation. Within the perceptual learning paradigm, listeners are exposed to p-initial words in English produced by a native speaker of French. Critically, listeners are trained on these words with either invariant or highly-variable VOTs. While a gross boundary shift is made for participants exposed to the variable VOTs, no such shift is observed after exposure to the invariant stimuli. These data suggest that increasing variation improves the mapping of perceptually mismatched stimuli.     

From blooming,buzzing confusion to media literacy: The early development of television viewing

Television comprehension is a surprisingly demanding task for very young children. Based on a task analysis of television viewing and review of research, we suggest that by 6 months of age, infants can identify objects and people on screen. By 24 months they can comprehend and imitate simple actions contained in single shots and begin to integrate information across shots. Toddlers nevertheless suffer from the video deficit whereby their comprehension is less than from equivalent real life displays. During the preschool years they learn much of the grammar of filmic montage and can comprehend straightforward narrative productions. Essentially adult comprehension appears to be in place by 13 years of age.     

Measuring consciousness: Is one measure better than the other?

What is the best way of assessing the extent to which people are aware of a stimulus? Here, using a masked visual identification task, we compared three measures of subjective awareness: The Perceptual Awareness Scale (PAS), through which participants are asked to rate the clarity of their visual experience; confidence ratings (CR), through which participants express their confidence in their identification decisions, and Post-decision wagering (PDW), in which participants place a monetary wager on their decisions. We conducted detailed explorations of the relationships between awareness and identification performance, looking to determine (1) which scale best correlates with performance, and (2) whether we can detect performance in the absence of awareness and how the scales differ from each other in terms of revealing such unconscious processing. Based on these findings we discuss whether perceptual awareness should be considered graded or dichotomous. Results showed that PAS showed a much stronger performance-awareness correlation than either CR or PDW, particularly for low stimulus intensities. In general, all scales indicated above-chance performance when participants claimed not to have seen anything. However, such above-chance performance only showed when we also observed a correlation between awareness and performance. Thus (1) PAS seems to be the most exhaustive measure of awareness, and (2) we find support for above-chance performance in the absence of subjective awareness, but such unconscious knowledge only contributes to performance when we observe conscious knowledge as well. Similarities and differences between scales are discussed in the light of consciousness theories and response strategies.     

Partial awareness distinguishes between measuring conscious perception and conscious content: Reply to Dienes and Seth

In their comment on Sandberg, Timmermans, Overgaard, and Cleeremans (2010), Dienes and Seth argue that increased sensitivity of the Perceptual Awareness Scale (PAS) is a consequence of the scale being less exclusive rather than more exhaustive. According to Dienes and Seth, this is because PAS may measure some conscious content, though not necessarily relevant conscious content, “If one saw a square but was only aware of seeing a flash of something, then one has not consciously seen a square.” In this reply, we claim that there is a difference between conscious visual experience, which may be partial, and the resulting conscious content, which is conceptual. Whereas PAS measures the first, confidence judgments and post-decision wagering measure the second.     

Subjective discriminability of invisibility: A framework for distinguishing perceptual and attentional failures of awareness

Conscious visual perception can fail in many circumstances. However, little is known about the causes and processes leading to failures of visual awareness. In this study, we introduce a new signal detection measure termed subjective discriminability of invisibility (SDI) that allows one to distinguish between subjective blindness due to reduction of sensory signals or to lack of attentional access to sensory signals. The SDI is computed based upon subjective confidence in reporting the absence of a target (i.e., miss and correct rejection trials). Using this new measure, we found that target misses were subjectively indistinguishable from physical absence when contrast reduction, backward masking and flash suppression were used, whereas confidence was appropriately modulated when dual task, attentional blink and spatial uncertainty methods were employed. These results show that failure of visual perception can be identified as either a result of perceptual or attentional blindness depending on the circumstances under which visual awareness was impaired.     

Perceptual biases in processing facial identity and emotion

Normal observers demonstrate a bias to process the left sides of faces during perceptual judgments about identity or emotion. This effect suggests a right cerebral hemisphere processing bias. To test the role of the right hemisphere and the involvement of configural processing underlying this effect, young and older control observers and patients with right hemisphere damage completed two chimeric faces tasks (emotion judgment and face identity matching) with both upright and inverted faces. For control observers, the emotion judgment task elicited a strong left-sided perceptual bias that was reduced in young controls and eliminated in older controls by face inversion. Right hemisphere damage reversed the bias, suggesting the right hemisphere was dominant for this task, but that the left hemisphere could be flexibly recruited when right hemisphere mechanisms are not available or dominant. In contrast, face identity judgments were associated most clearly with a vertical bias favouring the uppermost stimuli that was eliminated by face inversion and right hemisphere lesions. The results suggest these tasks involve different neurocognitive mechanisms. The role of the right hemisphere and ventral cortical stream involvement with configural processes in face processing is discussed.     

Perceptual grouping and distance estimates in typical and atypical development: comparing performance across perception, drawing and construction tasks

Perceptual grouping is a pre-attentive process which serves to group local elements into global wholes, based on shared properties. One effect of perceptual grouping is to distort the ability to estimate the distance between two elements. In this study, biases in distance estimates, caused by four types of perceptual grouping, were measured across three tasks, a perception, a drawing and a construction task in both typical development (TD: Experiment 1) and in individuals with Williams syndrome (WS: Experiment 2). In Experiment 1, perceptual grouping distorted distance estimates across all three tasks. Interestingly, the effect of grouping by luminance was in the opposite direction to the effects of the remaining grouping types. We relate this to differences in the ability to inhibit perceptual grouping effects on distance estimates. Additive distorting influences were also observed in the drawing and the construction task, which are explained in terms of the points of reference employed in each task. Experiment 2 demonstrated that the above distortion effects are also observed in WS. Given the known deficit in the ability to use perceptual grouping in WS, this suggests a dissociation between the pre-attentive influence of and the attentive deployment of perceptual grouping in WS. The typical distortion in relation to drawing and construction points towards the presence of some typical location coding strategies in WS. The performance of the WS group differed from the TD participants on two counts. First, the pattern of overall distance estimates (averaged across interior and exterior distances) across the four perceptual grouping types, differed between groups. Second, the distorting influence of perceptual grouping was strongest for grouping by shape similarity in WS, which contrasts to a strength in grouping by proximity observed in the TD participants.