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Near-misses in slot machines resemble jackpot wins but fall just short. Previous research has demonstrated that near-misses are behaviorally reinforcing despite the absence of monetary reward. We assessed the hedonic properties of near-misses by measuring the time between outcome delivery and the initiation of the next spin-the post-reinforcement pause (PRP) and skin conductance responses (SCRs) for losses, near-misses, and a range of wins (5, 15, 25, 50 or 250 credits) while participants (N = 122) played a slot machine simulator. PRPs and SCRs were compared for 40 low frequency and 22 high frequency slots players who were non-problem gamblers, 37 at risk players, and 23 problem gamblers. For winning outcomes, PRPs and SCRs tracked monotonically with win size such that progressively larger wins were associated with progressively larger PRPs and SCRs. Near-misses with jackpot symbols landing on the first two reels had significantly larger SCRs than regular losses, and other types of near misses. Crucially, PRPs for this kind of near-miss were significantly smaller than all wins, and when non-parametric statistics were used, significantly smaller than regular losses. This pattern of large SCRs and small PRPs suggest that these are highly frustrating outcomes that stimulate appetitive components of the reward system to promote continued gambling.

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The Guilty Knowledge polygraph test (GKT) and a variation of the test, the Guilty Actions Test (GAT), were compared in a laboratory setting. 84 men who committed or witnessed a mock crime answered "No", repeated items, or remained silent in response to items on the GKT or GAT. A monetary reward was promised for appearing innocent on the test. An interaction with scores based on skin resistance showed that innocent witnesses tested on the GKT scored more in the guilt direction than subjects in any other groups. Subjects required to say "no" were more reactive to key items than subjects in the item repetition or silence groups. Thoracic respiration scores showed a difference between guilty and innocent subjects.

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The guilty knowledge polygraph test (GKT; D. T. Lykken, 1959, 1960) is a psychophysiological method of identifying suspects with concealed information about a crime. A meta-analysis of 50 treatment groups drawn from 22 laboratory simulation studies (total N = 1,247) was conducted to provide a comprehensive estimate of GKT accuracy under controlled conditions. Electrodermal measures correctly identified 76% of participants with concealed knowledge and 83% of those without information. Informed participants were detected at rates significantly in excess of chance, with a mean weighted effect size of .57. Enactment of mock crimes increased the hit rate to 82%. The rates of false-positive error among noninformed treatment groups did not significantly exceed chance. Applications and research directions are discussed.

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