The present study examined the degree to which varying amounts of jackpot size would impact the rate and subjective probability of slot machine play in recrea-tional gamblers. Twenty college undergraduates who reported occasional slot machine playing served as participants. Two groups of 10 participants were utilized with each group exposed to one of two monetary contingencies (0.50USDversus2.00 USD). Various behavioral measures (e.g., inter-response times, subjective probabilities) were measured on each individual trial, and re-sistance to extinction was also examined. A significant difference of trial out-come (following losses and following wins) was found in respect to inter-response time in that inter-response times were significantly greater following winning trials (i.e., spins) than losing trials, and this difference was not miti-gated by jackpot size. Jackpot size only altered responding to near-miss jack-pots during extinction conditions. Implications for the treatment of pathological gamblers are presented
