Effects of unit formation on the perception of a changing sound

The effects of subunit formation on adult listeners' ability to notice changes in a continuous spectral gradient of sound were studied. Results of this experiment support the idea that the auditory system processes information differently within a unit, and that this processing does not occur unless the perceptual system detects unit boundaries. In this experiment, silences were inserted into a continuously changing sound to cause the formation of short units. Listeners noticed the change earlier in conditions with silences inserted than in to conditions where the transition was either unbroken or broken by loud noise bursts. Results are discussed in terms of two processes, one that accentuates stimulus properties present at moments of onset and offset, and a second that uses onsets and offsets to signal the beginnings and ends of units and reduces the change perceived within units.     

The associated nontargets effect: Evidence of nontarget processing at and beyond the level of letter recognition

In four visual search tasks participants were asked to make a target response if either of two targets was present and to make a nontarget response if neither target was present. Some target-absent displays included only nontarget stimuli or features that never occurred in the same displays as targets, whereas other target-absent displays included nontarget stimuli or features that did sometimes occur with targets. Nontarget responses were reliably faster in the former case than in the latter. This “associated nontargets effect” indicates that nontargets are not simply classified as nontargets but in addition are discriminated from one another. Current visual search models may underestimate the degree to which nontargets are processed during search.     

When attractiveness demands longer looks: The effects of situation and gender

We investigated how aesthetics guides our exploration of the environment. We embedded attractive and nonattractive faces into complex, real-world scenes and measured eye movements during scene viewing. We examined whether attractive faces would elicit longer looks, which would suggest that the aesthetic response orients people toward the rewarding and pleasing aspects of the environment. Experiment 1 showed that mean fixation, mean first fixation, and total fixation durations were longer to attractive faces, and fixations were longest to female faces and by female perceivers. In Experiment 2, we examined whether these effects of attractiveness are sensitive to situational factors. When perceivers were subjected to a threat or social approach manipulation prior to viewing the scenes, we confirmed specific hypotheses concerning the two manipulations. In accordance with the hypothesis that males have higher aggression potential than females, there were no differences in fixation durations between attractive and nonattractive male faces in the threat condition. On the other hand, in the social approach condition, both female and male attractive faces received longer looks. These results suggest that the aesthetic response orients people not only to the pleasing aspects of their environment, but also to those features that are adaptively relevant.     

Developmental changes in the control of saccadic eye movements in response to directional eye gaze and arrows

We investigated developmental differences in oculomotor control between 10-year-old children and adults using a central interference task. In this task, the colour of a fixation point instructed participants to saccade either to the left or to the right. These saccade directions were either congruent or incongruent with two types of distractor cue: either the direction of eye gaze of a centrally presented schematic face, or the direction of arrows. Children had greater difficulties inhibiting the distractor cues than did adults, which revealed itself in longer saccade latencies for saccades that were incongruent with the distractor cues as well as more errors on these incongruent trials than on congruent trials. Counter to our prediction, in terms of saccade latencies, both children and adults had greater difficulties inhibiting the arrow than the eye gaze distractors.     

Social event segmentation

Humans are experts in understanding social environments. What perceptual and cognitive processes enable such competent evaluation of social information? Here we show that environmental content is grouped into units of “social perception”, which are formed automatically based on the attentional priority given to social information conveyed by eyes and faces. When asked to segment a clip showing a typical daily scenario, participants were remarkably consistent in identifying the boundaries of social events. Moreover, at those social event boundaries, participants' eye movements were reliably directed to actors' eyes and faces. Participants' indices of attention measured during the initial passive viewing, reflecting natural social behaviour, also showed a remarkable correspondence with overt social segmentation behaviour, reflecting the underlying perceptual organization. Together, these data show that dynamic information is automatically organized into meaningful social events on an ongoing basis, strongly suggesting that the natural comprehension of social content in daily life might fundamentally depend on this underlying grouping process.     

Further attempts to clarify the importance of category variability for categorisation

The issue of how category variability affects classification of novel instances is an important one for assessing theories of categorisation, yet previous research cannot provide a compelling conclusion. In five experiments we reexamine some of the factors thought to affect participant performance. In Experiments 1 and 2, participants almost always classified the test item as belonging to the high variability category. By contrast, in Experiment 3 we employed an alternative experimental paradigm, where the difference in variability of the two categories was less salient. In that case, participants tended to classify a test item as belonging to the low variability category. Two additional experiments (4 and 5) explored in detail the differences between Experiments 1, 2 on the one hand, and 3 on the other. Some insight into the underlying psychological processes can be provided by computational models of categorisation, and we focus on the continuous version of Anderson's (1991) Rational Model, which has not been explored before in this context. The model predicts that test instances exactly halfway between the prototypes of two categories should be classified into the more variable category, consistent with the bulk of empirical findings. We also provided a comparison with a slightly reduced version of the Generalised Context Model (GCM) to show that its predictions are consistent with those from the Rational Model, for our stimulus sets.     

Risk aversion in information seeking

The information gain model argues that participants select alternatives with a larger expected value of information gain. The present study investigated risk aversion in information seeking to examine whether the expected value always determines information-seeking behaviour. For this investigation, we used a scale method selection task in which participants were required to select one of two scales for weighing coins in order to find an underweight coin. Two experiments showed that participants more frequently selected the alternative that provided information gain without risk, although its expected information gain was smaller. This finding indicates the presence of risk aversion in information seeking, suggesting that information-seeking behaviour is affected by risk associated with obtaining information gain.     

Digit Span and Articulatory Suppression: A Cross-linguistic Comparison

Information Reduction, a performance-enhancing cognitive strategy which develops with practice, is thought to be consciously and abruptly adopted and then applied consistently. Previous investigations used an Alphabet Verification Task where one observation was that not everyone adopts the strategy, but reasons for this are unclear. We demonstrated Information Reduction in three other tasks, confirming that it is not task-specific. Post-testing questionnaires probed verbally expressible knowledge, to gauge conscious awareness of any strategy. Overall, results indicate considerable variation in Information Reduction usage: Some individuals discovered and used the strategy and could verbally express this, others chose not to use it and some appeared to use it without awareness of doing so. Results also indicate that Information Reduction is not consistently applied, suggesting it is less robust than has been proposed. Our results may be better explained by a theory of practice learning which incorporates both data-driven automaticity and top-down controlled processes.     

The relation of learning disabilities to the long-term outcomes of concussion

ObjectiveThis study sought to cross-sectionally evaluate the relation between learning disorders (LD) and long-term concussion outcomes.MethodSeventy-three asymptomatic male university athletes (23 history of concussion with LD; 24 history of concussion no LD; 26 controls) completed the Beck Depression Inventory-2 (BDI-II), the Profile of Mood States (POMS), the Cogstate battery, and an Oddball task during which event-related brain potentials were recorded.ResultsConcussed athletes with LD exhibited greater depressive symptoms (BDI-II), greater total mood disturbance (POMS), decreased accuracy on the One-Card Learning and the N-back task (Cogstate), decreased accuracy on the Oddball task, and reduced ERN amplitude relative to both the concussed athletes without a LD and controls. Concussed athletes with LD also exhibited prolonged P3 latency relative to controls. Irrespective of LD, concussed athletes exhibited increased anger-hostility and decreased Pe amplitudes relative to controls. No differences were observed in P3a amplitude or latency.ConclusionHaving LD may be a significant factor moderating the neurophysiological, cognitive and psycho-affective outcomes of concussion, and may explain a significant portion of the persistent deficits observed by researchers and clinicians.