The current study evaluated whether robotic guidance can influence movement planning and/or the use of online proprioceptive feedback. Participants were divided into three groups wherein they practiced an aiming task unassisted or via a robotic device that led them through a trajectory with an asymmetric or symmetric velocity profile. Baseline performance was measured prior to training and a post-test included control and tendon vibration trials. Temporal, spatial, and kinematic variables were used to assess planning and online control mechanisms. Results indicated that tendon vibration altered the way individuals planned their movements and used online sensory feedback. Robotic-guided groups appeared to use online feedback to a lesser extent than the unassisted group during tendon vibration trials, based on kinematic data. Individuals may become less inclined to use erroneous proprioceptive feedback following robotic guidance, supporting the potential benefit of robotics in neuro-motor rehabilitation for those with proprioceptive deficits.

SFWT Zebrafish were exposed to various concentrations of EtOH at 24 hours post-fertilization for a period of two hours. When fish reached maturity they were placed in individual tanks in a larger open field. A preliminary strain comparison was also conducted using control (EtOH untreated) SFWT and AB fish. The behaviour of fish was recorded for 24 hours during a normal light:dark cycle. Motor patterns and general activity were quantified and analyzed and several behaviors were found to change significantly throughout the daytime and nighttime period. Also, fish exposed to the highest concentration of alcohol were found to exhibit significantly reduced amount of thrashing towards other subjects as compared to fish in the control group confirming previous results that demonstrated reduction of shoaling after early embryonic alcohol exposure.

Previous research on mind wandering has used subjective verbal reports as a means to acquire the frequency and rate of its occurrence. I proposed the use of eye movements as an objective measure of mind wandering while participants attempted a reading task. Participants were placed in a self-classified probe-caught mind wandering paradigm while their eye movements were recorded. They were randomly probed every 2-3 minutes and were required to indicate whether their mind had been wandering before they were allowed to continue reading. The overall pattern showed that eye movement behaviour was slower and less frequent when participants reported mind wandering episodes, with duration and frequency of within-word regressions reaching levels of statistical significance. It may be that the cognitive processes that normally guide eye movements during reading exert less control during mind wandering episodes. Other implications and limitations are discussed.

Current theories of auditory attention are largely based upon studies examining either the presentation of a single auditory stimulus or requiring the identification and labeling of stimuli presented sequentially. Whether or not these theories apply in more complex ecologically-valid environments where multiple sound sources are simultaneously active is still unknown. This study examined the pattern of neuromagnetic responses elicited when participants had to perform a search in an auditory language-based `scene` for a stimulus matching an imperative target held in working memory. The analysis of source waveforms revealed left lateralized patterns of activity that distinguished target present from target absent trials. Similar source waveform amplitudes were found when the target was presented in the left or right hemispace. The results suggest that auditory search for speech sounds engage a left lateralized process in the superior temporal gyrus.

The research focuses on the role of top-down influences on selective attention across the attentional visual field. The attentional visual field is the subset of the visual field in which attentional processes take place. The size of the attentional visual field is relatively large compared to the areas considered by most empirical studies of visual attention to date. Three possible forms of top-down influence are examined: 1) the expectation of the size of the area in which the target is likely to occur; 2) the expectation of the direction in which the target is likely to occur; and 3) existing unconscious bias in the spatial distribution of attention. Results from Experiment 1 suggest that participants modify the size of the attended area according to their expectation of the location of the target. Experiment 2 demonstrates that focus of attention can be oriented toward the expected target direction. Experiment 3 reveals that, even when no conscious control is involved, the distribution of attention is biased toward certain areas. Theoretical considerations are discussed, including the introduction of a simple statistical model to assist in conceptualizing the modifications of the distribution of attention over the attentional visual field. Practical applications of the results are also discussed.

Many people who sustain traumatic brain injuries (TBI) have poor psychosocial outcomes. Previous research has indicated that poor outcomes are related to the use of avoidant coping following TBI, although the mechanisms of this relationship are not clear. The major pathological consequence of TBI is damage to the frontal lobes and/or their connections, resulting for most people in executive and/or affective dysfunction. The purpose of this dissertation study was to delineate the neuropsychological, psychiatric, personality and physiological mechanisms of avoidant coping following TBI. Controls and people with TBI completed the Baycrest Psychosocial Stress Test (BPST), where coping behaviour was observed directly, and physiological measures were recorded. Participants also completed a neuropsychological test battery, and a series of questionnaires assessing coping, psychiatric status, personality and outcomes. There were no significant differences between groups in self reported coping. However, the control and mild TBI group engaged in more planful than avoidant behaviour on the BPST. As a group, individuals with moderate-to-severe injury, in contrast, engaged in more avoidant than planful behaviour. However, analysis of individual differences in coping behaviour within the moderate-to-severe group revealed a bimodal distribution, allowing classification of people in this group as ‘planners’, or ‘avoiders’ (this distribution was not evident in the mild TBI group). Within the moderate-to-severe group, planners had better executive function, were more reactive to stress (psychologically and physiologically), performed better on the speech task during the BPST, and had greater return to productivity. However, planners also had worse psychosocial outcomes as compared to the avoiders. This was the first study, to the author’s knowledge, to examine coping behaviour during a simulated real-world stress test. Results indicate that behavioural measures of coping, such as the BPST, are more sensitive to changes in coping post TBI than are self and significant other reported questionnaires. Results also demonstrate that executive function and psychological and physiological reactivity are important factors that contribute to coping following moderate-to-severe TBI. These data raise important questions about the challenges of targeting coping through rehabilitation.

The research focuses on the role of top-down influences on selective attention across the attentional visual field. The attentional visual field is the subset of the visual field in which attentional processes take place. The size of the attentional visual field is relatively large compared to the areas considered by most empirical studies of visual attention to date. Three possible forms of top-down influence are examined: 1) the expectation of the size of the area in which the target is likely to occur; 2) the expectation of the direction in which the target is likely to occur; and 3) existing unconscious bias in the spatial distribution of attention. Results from Experiment 1 suggest that participants modify the size of the attended area according to their expectation of the location of the target. Experiment 2 demonstrates that focus of attention can be oriented toward the expected target direction. Experiment 3 reveals that, even when no conscious control is involved, the distribution of attention is biased toward certain areas. Theoretical considerations are discussed, including the introduction of a simple statistical model to assist in conceptualizing the modifications of the distribution of attention over the attentional visual field. Practical applications of the results are also discussed.

Before the 1990s controlled research using mock jurors consistently found black defendants guilty more often than white. However, more recently, research has generally failed to find this effect. One explanation is that prejudice has been reduced so much that there is no longer an effect. While there does seem to have been a reduction in overt prejudice, it is unlikely that it has decreased to the point that it does not affect verdicts. A more likely explanation is that strong social norms exist concerning prejudice which result in efforts to avoid being (or appearing) biased. Thus, when motivation to reduce prejudice is salient, mock jurors and perhaps real jurors will display little or no prejudice; but when motivation to reduce prejudice is not salient, decision-making becomes spontaneous and whatever prejudice does exist will affect decisions. In a series of 6 studies, race of defendant, race of witness, and the salience of the importance of being unbiased were varied. Results revealed a complex situation with many factors playing a part. Race of key alibi witness played a key role, with the white witness favoured, and the black witness mistrusted. Outcomes may be partially predicted based on Social Dominance Orientation (SDO). Those high in SDO treat incongruent defendant/witness race pairs more harshly than congruent race pairs. Modern apparently egalitarian outcomes are perhaps due to low prejudice participants’ bias in favour of black defendants while high prejudice participants were biased against black defendants – effectively cancelling out each others’ verdicts. Those low in SDO treat incongruent defendant/witness race pair too leniently as compared to congruent race pairs. When race is made salient, bias is reduced, and though the average results are still essentially egalitarian, these verdicts are more truly egalitarian – much fairer and less biased when considered at an individual level. These results also reinforce theories of dual process models of attitudes. Individuals may have common stereotype knowledge, but separate activation based on prejudice levels. Both high and low prejudiced individuals can control bias with the proper motivation.

Before the 1990s controlled research using mock jurors consistently found black defendants guilty more often than white. However, more recently, research has generally failed to find this effect. One explanation is that prejudice has been reduced so much that there is no longer an effect. While there does seem to have been a reduction in overt prejudice, it is unlikely that it has decreased to the point that it does not affect verdicts. A more likely explanation is that strong social norms exist concerning prejudice which result in efforts to avoid being (or appearing) biased. Thus, when motivation to reduce prejudice is salient, mock jurors and perhaps real jurors will display little or no prejudice; but when motivation to reduce prejudice is not salient, decision-making becomes spontaneous and whatever prejudice does exist will affect decisions. In a series of 6 studies, race of defendant, race of witness, and the salience of the importance of being unbiased were varied. Results revealed a complex situation with many factors playing a part. Race of key alibi witness played a key role, with the white witness favoured, and the black witness mistrusted. Outcomes may be partially predicted based on Social Dominance Orientation (SDO). Those high in SDO treat incongruent defendant/witness race pairs more harshly than congruent race pairs. Modern apparently egalitarian outcomes are perhaps due to low prejudice participants’ bias in favour of black defendants while high prejudice participants were biased against black defendants – effectively cancelling out each others’ verdicts. Those low in SDO treat incongruent defendant/witness race pair too leniently as compared to congruent race pairs. When race is made salient, bias is reduced, and though the average results are still essentially egalitarian, these verdicts are more truly egalitarian – much fairer and less biased when considered at an individual level. These results also reinforce theories of dual process models of attitudes. Individuals may have common stereotype knowledge, but separate activation based on prejudice levels. Both high and low prejudiced individuals can control bias with the proper motivation.

Competing speech seems to pose a greater challenge to spoken language comprehension than does competing noise, especially for older adults. The difficulties of older adults may be due to declines in auditory and cognitive processing. However, evidence suggests that the use of top-down information processing to overcome this interference may be preserved in aging. This research investigated the effect of speech- and noise masking on language comprehension, as well as age-related differences in the use of top-down processing to overcome masking. Topic I examined whether younger and older adults gain the same release from masking given a partial preview of a target sentence in quiet (auditory prime) prior to hearing the full sentence in noise, and investigated the auditory factors contributing to the advantage provided by the primes. Results showed that despite age-related declines in overall performance, younger and older listeners benefited similarly from priming. This benefit was not attributable to cues about the target talker’s voice or fluctuations in the amplitude envelope of the target sentences. Topics II and III examined the effect of speech- and noise masking on the time-course of stream segregation. The analyses revealed that stream segregation takes time to build up when a speech target is masked by other speech, but not when it is masked by noise. Subsequent analyses showed that in younger adults, the delay in segregation under speech masking was primarily due to the vocal similarities between the talkers, with interference from the semantic content of the masker playing a secondary role in impeding performance. The results also showed that older listeners were less efficient than younger listeners in segregating speech from speech-like maskers. Furthermore, older listeners benefited less than younger listeners when the amplitude envelope modulations of maskers were limited. Overall, the findings indicate that some of the language comprehension difficulties experienced by older listeners in noisy environments may be due to age-related declines in stream segregation and a decreased ability to benefit from fluctuations in the amplitude envelopes of maskers. However, benefit from priming may help offset some of these age-related declines in auditory scene analysis.