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Previous research has established that observing another in pain activates both affective and sensorimotor cortical activity that is also present during the first-hand experience of pain. Some researchers have taken this “mirroring” response as indicative of empathic processing. However, very little work has explored the downstream behavioral effects of empathic pain observation. The aim of this dissertation is to begin to fill this gap in the literature by exploring the relationship between empathic pain observation, overt motor behaviours, and sensorimotor activity. In chapters 2-4, I provide robust evidence that observing pain inflicted on another person leads to faster reaction time responses. This effect is shown to be temporally extended (by at least 500ms after pain observation), effector-general (affecting both finger and foot responses), influenced by top-down (i.e., instructions to explicitly empathize) but not bottom-up (i.e., the perceived level of pain) factors, and is not influenced by adaptive (approach/withdraw) behaviours. In chapter 5, I show that sensorimotor activity, measured via TMS-induced Motor Evoked Potentials, increases while observing another in pain regardless whether the observer is preparing to make an action vs. passively observing the stimuli. These results run counter to the literature, and I provide several explanations for why these results were found. Lastly, in chapter 6, I show that sensorimotor activity, measured via Mu and Beta suppression, also increases while observing another in pain regardless whether the observer is preparing to make an action vs. passively observing the stimuli. Interestingly, I do not find significant correlations between sensorimotor activity during pain observation and faster reaction times after pain observation. I embed these findings in relation to the wider social neuroscience of empathy literature and discuss several limitations and challenges in empirically measuring “empathy” as a psychological construct. Overall, this dissertation furthers our understanding of empathy for pain by highlighting the behavioural consequences of pain observation and its connection (or rather, lack thereof) to sensorimotor activity during pain observation. / Thesis / Doctor of Philosophy (PhD) / Past research suggests that overlapping brain activity during the first-hand experience of pain and pain observation may be indicative of empathy. However, very little work has been done to explore how pain observation influences overt behaviours. This thesis investigates this issue by having participants complete a reaction time task while watching videos of needles stabbing a person’s hand. The findings reported in this thesis suggests that observing another in pain facilitates motor behaviours (i.e., faster reaction times); this facilitation extends 500ms after pain observation, affects both the hand and feet, is accentuated by instructing participants to explicitly empathize, and is not influenced by approach vs. withdraw movements. Brain activity in the motor system was also found to increase during pain observation. Overall, this thesis begins the discussion of how empathic pain observation influences explicit motor behaviours, and how such behaviours may be related to brain activity.

No / Which is better, a visual or an auditory warning signal? Initial findings suggested that an auditory signal was more effective, speeding reaction to a target more than a visual warning signal, particularly at brief foreperiods [Bertelson, P., & Tisseyre, F. (1969). The time-course of preparation: confirmatory results with visual and auditory warning signals. Acta Psychologica, 30. In W.G. Koster (Ed.), Attention and Performance II (pp. 145-154); Davis, R., & Green, F. A. (1969). Intersensory differences in the effect of warning signals on reaction time. Acta Psychologica, 30. In W.G. Koster (Ed.), Attention and Performance II (pp. 155-167)]. This led to the hypothesis that an auditory signal is more alerting than a visual warning signal [Sanders, A. F. (1975). The foreperiod effect revisited. Quarterly Journal of Experimental Psychology, 27, 591-598; Posner, M. I., Nissen. M. J., & Klein, R. M. (1976). Visual dominance: an information-processing account of its origins and significance. Psychological Review, 83, 157-171]. Recently [Turatto, M., Benso, F., Galfano, G., & Umilta, C. (2002). Nonspatial attentional shifts between audition and vision. Journal of Experimental Psychology; Human Perception and Performance, 28, 628-639] found no evidence for an auditory warning signal advantage and showed that at brief foreperiods a signal in the same modality as the target facilitated responding more than a signal in a different modality. They accounted for this result in terms of the modality shift effect, with the signal exogenously recruiting attention to its modality, and thereby facilitating responding to targets arriving in the modality to which attention had been recruited. The present study conducted six experiments to understand the cause of these conflicting findings. The results suggest that an auditory warning signal is not more effective than a visual warning signal. Previous reports of an auditory superiority appear to have been caused by using different locations for the visual warning signal and visual target, resulting in the target arriving at an unattended location when the foreperiod was brief. Turatto et al.'s results were replicated with a modality shift effect at brief foreperiods. However, it is also suggested that previous measures of the modality shift effect may still have been confounded by a location cuing effect.

The present study assessed the impact of aging on cognitive functioning over six to 16 years in exceptionally healthy individuals (20 to 79 years) drawn from the Baltimore Longitudinal Study of Aging. The first study (N = 380 women, 757 men) examined the relationship between age and speed of processing as measured by five reaction time (RT) tasks (simple reaction time to complex reaction time involving varying amounts of inhibitory and working memory processing). Unlike previous research, this study additionally assessed the impact of processing speed, working memory, inhibitory processing, and interference RT measures in predicting future performance 6-16 years later (N=103) on (1) mental status (Blessed Information-Memory-Concentration, Mini-Mental State Examination), and prefrontal mediated neuropsychological tests (Trail Making A and B; verbal and category fluency; WAIS digits forward and backwards, California Verbal Learning Test proactive interference index). Regression analyses assessed which theoretical approach, speed of processing (Salthouse, 1996) or prefrontal cortex (Hasher & Zacks, 1988; West, 1996), better explained cognitive change. Age-related cognitive slowing was observed for initial RT tasks. Especially among the oldest studied (62-79 years of age), slower speed of processing was accelerated by task complexity. Increases in response time were substantially steeper for older as opposed to younger participants. Men were faster than women were on simple RT and a RT task that involved inhibitory processing. A 6-9 year age decline in speed of processing only occurred among individuals over 60 years. RT omission and commission errors showed similar results. Hierarchical regression analyses determined that RT tasks involving inhibitory control, working memory and interference were most predictive of future prefrontal-mediated cognitive performance (Trail Making B, digit span backwards, letter and category fluency). Prediction of the prefrontal outcome measures of Trail Making A and digit span forward performance from simple reaction time was mediated by the RT measures (inhibitory control, working memory and interference), but not the other way around. Thus, the data most strongly support the Inhibitory Deficit (Hasher & Zacks, 1988) and Prefrontal Cortex Function (West, 1996) theories. There was little support for the processing speed theory (Salthouse, 1996). / Ph. D.

The onset of a yellow indication is typically associated with the risk of vehicle crashes resulting from dilemma-zone and red-light-running problems. Such risk of vehicle crashes is greater for high-speed signalized intersection approaches. The research presented in this dissertation develops statistical as well as behavioral frameworks for modeling driver behavior while approaching high-speed signalized intersection approaches at the onset of a yellow indication. The analysis in this dissertation utilizes two sources of data. The main source is a new dataset that was collected as part of this research effort during the summer of 2008. This experiment includes two instructed speeds; 72.4 km/h (45 mph) with 1727 approaching trials (687 running and 1040 stopping), and 88.5 km/h (55 mph) with 1727 approaching trials (625 running and 1102 stopping). The complementary source is an existing dataset that was collected earlier in the spring of 2005 on the Virginia Smart Road facility. This dataset includes a total of 1186 yellow approaching trials (441 running and 745 stopping). The adopted analysis approach comprises four major parts that fulfill the objectives of this dissertation. The first part is concerned with the characterization of different driver behavioral attributes, including driver yellow/red light running behavior, driver stop-run decisions, driver perception-reaction times (PRT), and driver deceleration levels. The characterization of these attributes involves analysis of variance (ANOVA) and frequency distribution analyses, as well as the calibration of statistical models. The second part of the dissertation introduces a novel approach for computing the clearance interval duration that explicitly accounts for the reliability of the design (probability that drivers do not encounter a dilemma zone). Lookup tables are developed to assist practitioners in the design of yellow timings that reflects the stochastic nature of driver PRT and deceleration levels. An extension of the proposed approach is presented that can be integrated with the IntelliDriveSM initiative. Furthermore, the third part of the dissertation develops an agent-based Bayesian statistics approach to capture the stochastic nature of the driver stop-run decision. The Bayesian model parameters are calibrated using the Markov Chain Monte Carlo (MCMC) slice procedure implemented within the MATLAB® software. In addition, two procedures for the Bayesian model application are illustrated; namely Cascaded regression and Cholesky decomposition. Both procedures are demonstrated to produce replications that are consistent with the Bayesian model realizations, and capture the parameter correlations without the need to store the set of parameter realizations. The proposed Bayesian approach is ideal for modeling multi-agent systems in which each agent has its own unique set of parameters. Finally, the fourth part of the dissertation introduces and validates a state-of-the-art behavioral modeling framework that can be used as a tool to simulate driver behavior after the onset of a yellow indication until he/she reaches the intersection stop line. The behavioral model is able to track dilemma zone drivers and update the information available to them every time step until they reach a final decision. It is anticipated that this behavioral model will be implemented in microscopic traffic simulation software to enhance the modeling of driver behavior as they approach signalized intersections. / Ph. D.

Twenty "normal" (non-hyperactive) preschool children (9 girls, 11 boys) and 6 schoolage boys were maintained on a low sucrose diet for two weeks. During the second week, subjects were randomly assigned to one of two treatments (drink sweetened with either sucrose or aspartame). Cherry-flavored drinks mixed in a distilled water base were given daily. Subjects in the sucrose group received 3.4 g sucrose per kilogram of body weight, mixed to a concentration of 25 g per 100 ml. Subjects in the aspartame group received the same cherry-flavored drink mixed to a concentration of 8 g of aspartame per 100 ml of drink. A simple reaction-time task measured attention and alertness three times during the study: (1) prior to the low sucrose diet; (2) after one week of the low sucrose diet; (3) after one week of receiving the treatment. The dependent variable was the difference between reaction time at time 3 (after treatment) and time 2 (at the end of one week of a low sucrose diet). An ANCOVA (2 levels of treatment, age as covariate) revealed no significant difference in the mean reaction times of the subjects in the sucrose and aspartame groups. However, the variance in reaction times for those in the sucrose treatment group was significantly greater (p̱< .03) than for those in the aspartame group. / Master of Science

Water is arguably the most important nutrient given that even minor deficits lead to performance detriment for athletes and, in a matter of days, total absence causes fatality for all. Despite this, several reports suggest that an overwhelming amount of the athletic population competes and trains in a dehydrated state. The impact of dehydration on leisure sports, such as golf, is less certain given that fine motor skill sports have received less attention in the literature and that existing research on dehydration and golfers is largely limited to males. In this randomized, controlled, crossover pilot experiment, elite female golfers on the Virginia Tech Women’s Golf Team (n=6) completed four laboratory simulated golf holes in both euhydrated and dehydrated states. Euhydration (mean urinary specific gravity [USG]=1.009; range=1.003–1.021) was attained by following the NCAA hydration guidelines, and dehydration (mean USG=1.021; range=1.018–1.026) was attained via a 12 hour overnight fast from fluids. No significant interactions of condition by time for perceived effort, 7-iron distance and accuracy, putting accuracy, reaction time, and executive cognitive function were found between euhydrated and dehydrated states. However, although not significant, euhydrated participants demonstrated improved 7-iron and putting accuracy and reported less perceived effort as compared to performance during their dehydrated state. Based on USG levels, NCAA hydration recommendations may not be adequate to induce a euhydrated state for all athletes. More research is needed with larger sample sizes to further elicit the impact of hydration status on variance in motor and cognitive function for elite golfers. / Masters of Science

No / PURPOSE. This study examined the influence of stimulus chromaticity on simple reaction times (RTs) to determine the stage of chromatic processing that is most influential in their generation. METHODS. Simple RTs were measured in response to the cosinusoidally ramped onset of small, equiluminant, colored Gaussian spots. The chromaticity of these stimuli was varied, to modulate along a series of vectors in color space that included red-green (L-M) and blue-yellow (S-[L+M]) opponent axes. RESULTS. RTs are highly sensitive to small departures from subjective equiluminance. They are also dependent on stimulus chromaticity. The longest RTs are generated in response to equiluminant stimuli that isolate S-cone activity, whereas the shortest are generated by stimuli that modulate the L-M opponent axis. However, temporal processing differences are highly dependent on how the chromatic stimuli are scaled in relation to one another. The differences are reduced when scaling is based on detection threshold. The relationship between chromatic contrast and RT can be described by the modified Piéron equation RT = RT0 + k · C-1. CONCLUSIONS. Simple RTs generated in this study conform to the idea that they are largely determined by cone-opponency mechanisms. The use of cone contrast as a metric for scaling chromatic stimuli exaggerates differences between the temporal responsiveness of L-M and S-(L+M) opponency mechanisms.

No / Differences in transduction and transmission latencies of visual, auditory and tactile events cause corresponding differences in simple reaction time. As reaction time is usually measured in unimodal blocks, it is unclear whether such latency differences also apply when observers monitor multiple sensory channels. We investigate this by comparing reaction time when attention is focused on a single modality, and when attention is divided between multiple modalities. Results show that tactile reaction time is unaffected by dividing attention, whereas visual and auditory reaction times are significantly and asymmetrically increased. These findings show that tactile information is processed preferentially by the nervous system under conditions of divided attention, and suggest that tactile events may be processed preattentively. / Wellcome Trust, Leverhulme Trust, College of Optometrists