Luke Clark
Relevant Thesis-Based Degree Programs
Affiliations to Research Centres, Institutes & Clusters
Great Supervisor Week Mentions
Last year, on Supervisor Appreciation Day, we dedicated our waiting area to @LukeClark01. This year, we re-dedicated it. We're so proud, we made mugs. Every grad student in the lab bought one. #GreatSupervisor #UBC
Well @LukeClark01, another Supervisor Appreciation Week is upon us. Without being overly cloying, here are 3 things I really like about working for you. #greatsupervisor #UBC
1. You put a huge amount of work into editing and improving our writing. Sorry I took 5 years to learn the difference between 'While' and 'Although.'
2. At least 3 or 4 times a year, you keep me from doing (or tweeting!) something that would seriously impact my career.
3. Your (almost encyclopedic) knowledge of papers (and authors... and journals...) is so impressive that I sometimes try to figure out exactly how you do it. Thanks, Luke!
A #GreatSupervisor deserves thanks, but an awesome supervisor deserves pranks. @LukeClark01, the lab thanks you for your effort. #ubc
Graduate Student Supervision
Doctoral Student Supervision
Dissertations completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest dissertations.
More than most gambling forms, Electronic Gaming Machines (EGMs, e.g. modern slot machines) have been linked to Gambling Disorder, a behavioural addiction recognized by the American Psychiatric Association. Immersion is a ‘trance-like’ state of extreme focus often reported in EGM gambling. Immersion in EGM gambling is a robust predictor of gambling problems, but is poorly understood. Few studies have investigated the cognitive, behavioural, and physiological correlates of this subjective state, and existing data rely on retrospective self-report. I investigated these topics, hypothesizing that immersion in EGM gambling produces measurable shifts in behaviour and physiological arousal, and that EGM immersion affects gamblers’ behaviour towards specific elements of the device.The first two experiments recruited samples of undergraduate students, and examined whether self-reported immersion during an EGM gambling session correlated with cardiac markers of sympathetic and parasympathetic nervous system activity. EGM gambling saw decreased parasympathetic nervous system activity irrespective of immersion. Changes in sympathetic activity were limited to the first few minutes of gambling, and were specifically associated with immersion. Additionally, higher rates of immersion were found when participants placed bets across multiple paylines, a feature endemic to modern EGMs.The third and fourth experiments recruited a sample of experienced EGM gamblers, who gambled on a real EGM while providing high-resolution eye tracking data. Immersion levels were associated with increased time spent looking at the EGM’s credit window, and decreased time on its spinning reels. Immersion was positively associated with the number of saccades participants made while gambling, as well as longer post-reinforcement pauses, a behavioural indicator of perceived reward value. We found that the EGM’s free spin bonus feature was associated with significant increases in pupil diameter, potentially indicating sympathetic nervous system arousal.Together, these experiments suggest that immersion is an active state characterized by increased reward-seeking. These data further link immersion to activity within the sympathetic nervous system, and show that immersion is impacted by specific features of modern EGMs. These results present novel candidate markers of immersion, both behavioural and physiological, and provide insight into the disproportionate rates of gambling problems associated with modern EGMs.
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Master's Student Supervision
Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.
The field of gambling studies is beginning to recognize the need to conduct targeted replications of influential effects throughout the field. Given the limited resources afforded to researchers, we must be systematic in our approach to selecting which effects are most in need of replication. Following a systematic approach to replication selection, a series of conceptual replications of the ‘near-miss effect’ in slot machine gambling was conducted, on online community samples. Near-miss outcomes on a slot machine are those that appear proximal to a win, though they are functionally identical to other losing outcomes (herein termed ‘full misses’). Near-misses have been shown to elicit a range of differential psychological effects compared to full-misses. Experiment 1a and 1b attempted to replicate a previous study by Clark et al. 2009 that 1) near-misses are experienced as more negative, 2) near-misses are rated as more motivating to continue playing a slot machine. Experiment 2 tested the effects on speed of gambling (a replication of Dixon et al. 2013) that near-miss outcomes speed up participant speed of play compared to full miss outcomes. Experiment 3 tested whether near-miss outcomes influence subsequent bet size. I replicated the motivation hypothesis of Clark et el., (2009), but found a significant effect in the opposite direction for the valence hypothesis. Across both study 1a and 1b, near-miss outcomes were more positive relative to full-misses. Experiment 2 replicated the hypothesis that near-miss outcomes increase speed of play (Dixon et al., 2013). Experiment 3 observed near-miss outcomes led to a significant increase in bet size on the subsequent spin relative to full-miss outcomes. I consider how this pattern of results across 3 different dependent variables speak to the different theoretical accounts of how near-misses operate.
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Gambling decisions are inherently risky decisions involving wins and losses. The severity of gambling problems varies with the persistence of betting despite mounting losses. ‘Prospect Theory’, a descriptive model of risky decision-making from the field of behavioural economics, describes an influential phenomenon called Loss Aversion: the natural tendency for “losses to loom larger than gains” when people evaluate risky choices (Kahneman and Tversky, 1992). It is an intuitive prediction that people with the more severe gambling problem will display systematic alterations in their loss aversion. Experiment 1 reviewed two widely-used loss aversion tasks (the ‘matrix’ and ‘staircase’ methods) in the past studies, which also have varied in whether trial-by-trial outcome feedback was presented within each task. Hence, Experiment 1 was a methodological study. It aimed to evaluate whether the presentation of outcome feedback influences loss aversion scores with student samples, as a precursor for Experiment 2 using this procedure in regular gamblers. Experiment 2 recruited non-problem gamblers with varying levels of sub-clinical gambling problems. With the established task, it studied the relationships between the severity of gambling problems and risk preferences including risk attitudes across the gain and loss domains, loss aversion, and probability distortions. In Experiment 1, the outcome feedback did not show significant influence on the level of loss aversion. In Experiment 2, the findings indicated that the risk attitudes in the gain domain were the only Prospect Theory-based variable that correlated with the severity of gambling problems; participants with more severe problems tended to be more risk-seeking in the gain domain, and in the loss domain, all participants displayed ambivalent choices between risk-seeking and risk-averse. Moreover, the level of loss aversion and the magnitudes of probability distortions for potential gains and losses did not correlate with the severity of gambling problems.
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Testosterone can be seen to modulate cognition and behaviour in many ways. One likely effect is to promote risky decision-making. According to a phenomenon termed the “winner-loser effect,” testosterone has also been observed to fluctuate in response to winning or losing competitions with others, with wins causing increases and losses causing decreases. Surprisingly, few studies have investigated the effects of gambling on testosterone levels, or whether individual differences in testosterone are related to risky gambling strategies. More specifically, the winner-loser effect may extend to slot machine gambling as a solitary gambling activity if players tend to ‘anthropomorphize’ slot machines, i.e. to treat the machine as a human agent with intentions and feelings. This study used a quasi-experimental design to measure testosterone fluctuations in response to winning and losing during a period of authentic slot machine gambling. Cortisol and anthropomorphism were investigated as potential moderators of a winner-loser effect on testosterone. Male participants (n = 120) provided saliva samples before and after a period of gambling on an authentic slot machine. Participants also provided measures of real-world gambling involvement, subjective experiences during slot machine play, and anthropomorphic tendencies. Contrary to predictions, winning and losing were not significantly associated with divergent effects on testosterone, even after considering cortisol levels and anthropomorphization of the slot machine. An exploratory analysis supported a link between positive affect (higher in winners) and decreases in testosterone, which suggested that the winner-loser effect may be reversed in slot machine gambling. In addition, baseline testosterone predicted a slower rate of gambling. The results of this study add to a growing literature on the boundary conditions of the winner-loser effect, which inform future examinations of the role of testosterone in gambling behaviour.
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