Post-print of: Haw, J 2008, 'The relationship between reinforcement and gaming machine choice ' , Journal of Gambling Studies, vol. 24, no. 1,. The original publication is available at www.springerlink.com, http://dx

The distribution of rewards in both variable-ratio and random-ratio schedules is examined with specific reference to gambling behaviour. In particular, it is the number of early wins and unreinforced trials that is suggested to be of importance in these schedules, rather than the often-reported average frequency of wins. Gaming machine data are provided to demonstrate the importance of early wins and unreinforced trials. Additionally, the implication of these distributional properties for betting strategies and the gambler's fallacy is discussed. Finally, the role of early wins and unreinforced trials is considered for gambling research that utilises simulated gaming machines and research that compares concurrent schedules of reinforcement.

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Previous studies of the relationship between impulsivity and problem gambling have produced inconsistent results due to sampling issues and the measures utilised. The current study assessed five facets of impulsivity as predictors of both gambling impaired control and problem gambling in a random sample of 309 regular EGM players. The measures included the UPPS-P for impulsivity, the PGSI for problem gambling and the impaired control scale from the SLUGS. This sample comprised 173 women (56 %) with a mean age of 59.15 years and 146 men with a mean age of 57.18 years. Results revealed that lack of perseverance was not a predictor of either gambling measure and that negative urgency was the strongest predictor of both impaired control and problem gambling. The negative urgency result is discussed in the context of the pathways models and the emotionally vulnerable problem gambler. It was also found that for the PGSI, positive urgency, lack of premeditation and sensation seeking were weaker, but still significant predictors. This result is discussed with regard to the use of the PGSI in predicting gambling behaviour and problems in the wording of the positive urgency facet of the UPPS-P.Impulsivity has been broadly defined as a Btendency to act spontaneously and without deliberation^([1], p. 13). It is considered to play an important role in the initiation of behaviour and to be a personality-based risk factor for a range of mental health disorders including substance abuse, pathological gambling, bulimia nervosa, attention deficit/ hyperactivity disorder, borderline and anti-social personality disorders [2][3][4][5]. In total, the DSM-IV had 18 separate disorders that included criteria related to a broad definition of impulsivity [6] and this underlines the importance of defining and measuring the trait.With the types of the behaviours associated with impulsivity being so varied there have been a number of different scales developed that attempt to measure the overall construct [2].