The near win effect on observing behaviour in simulated slot-machine gambling: The role of conditioned reinforcement

<p>Slot machines are a remarkably popular mode of gambling even though they are programmed to make a profit by paying out less money than is put in. One common feature of slot machines, which may increase the likelihood of persistent gambling in the face of this monetary loss, is the near win. This study’s aim was to investigate the conditioned reinforcing properties of near wins using an observing response procedure in the context of a simulated slot machine. In an observing response procedure, participants can use an observing button to produce a stimulus correlated with the availability of reinforcement (S+) or a stimulus correlated with no reinforcement or less reinforcement (S-). The percentage of observing responses made for each stimulus is thought to reflect the reinforcing efficacy of the reinforcer correlated with each stimulus. Experiment 1 successfully tested the procedure with an obvious reinforcer - wins - and found consistently more observing for the S+. In Experiment 2 and 3 the S+ was correlated with near wins, and in Experiment 2 only those with slot-machine experience had consistently more observing for the S+. Experiment 3 increased the probability of wins to enhance the reinforcing efficacy of near wins, but failed to find consistently more observing for the S+, regardless of slot machine or scratchie card experience. These results indicated that near wins are not conditioned reinforcers. However, participants tended to bet more following near wins than losses, which suggested that near wins may instead function as discriminative stimuli.</p>

The near win effect on observing behaviour in simulated slot-machine gambling: The role of conditioned reinforcement

<p>Slot machines are a remarkably popular mode of gambling even though they are programmed to make a profit by paying out less money than is put in. One common feature of slot machines, which may increase the likelihood of persistent gambling in the face of this monetary loss, is the near win. This study’s aim was to investigate the conditioned reinforcing properties of near wins using an observing response procedure in the context of a simulated slot machine. In an observing response procedure, participants can use an observing button to produce a stimulus correlated with the availability of reinforcement (S+) or a stimulus correlated with no reinforcement or less reinforcement (S-). The percentage of observing responses made for each stimulus is thought to reflect the reinforcing efficacy of the reinforcer correlated with each stimulus. Experiment 1 successfully tested the procedure with an obvious reinforcer - wins - and found consistently more observing for the S+. In Experiment 2 and 3 the S+ was correlated with near wins, and in Experiment 2 only those with slot-machine experience had consistently more observing for the S+. Experiment 3 increased the probability of wins to enhance the reinforcing efficacy of near wins, but failed to find consistently more observing for the S+, regardless of slot machine or scratchie card experience. These results indicated that near wins are not conditioned reinforcers. However, participants tended to bet more following near wins than losses, which suggested that near wins may instead function as discriminative stimuli.</p>

Contribution of Harman and Norharman to the Reinforcing Efficacy of Aqueous Tobacco Smoke Extract Self-Administered by Rats

<p>Background: Animal models of drug abuse treat nicotine as the primary reinforcing agent that promotes tobacco addiction. However, rodents demonstrate poor self-administration of nicotine despite evidence of tobacco's high abuse potential in humans. This discrepancy has been attributed to other constituents of tobacco smoke that facilitate the development of nicotine dependence. Objectives: This study aimed to determine whether rats would self-administer intravenous an aqueous tobacco smoke extract (TPM) to find evidence if it was more reinforcing than nicotine alone. The study also evaluated the role of tobacco smoke constituent’s harman and norharman in any differences observed. Methods: Firstly, male Sprague-Dawley rats (n=29) were assigned to treatment groups: nicotine (30.0μg/kg/infusion), TPM (containing 30.0μg/kg/infusion nicotine) or saline vehicle. Ability for each treatment to support intravenous self-administration was assessed using spontaneous acquisition of responding on gradually increasing fixed ratio schedules (FR1, FR2, FR5). Subsequent progressive ratio (PR) testing was employed to determine reinforcing efficacy of each treatment. Then a second group of rats (N = 56) were assigned to treatment groups: nicotine alone (30.0 or 75.0μg/kg/infusion) or nicotine combined with norharman (0, 0.4, 2.5 or 6.25μg/kg/infusion) and harman (0.0, 1.6 or 10.0μg/kg, IP), and tested using a similar protocol. Results: Animals readily acquired self-administration responding for TPM and produced higher PR breakpoints (BP) than rats treated with nicotine alone or vehicle. Rats trained to respond for a larger dose of nicotine demonstrated significantly greater response rates than those receiving the lower dose of nicotine. Finally, the addition of harman and norharman to nicotine significantly reduced BP at the lower unit dose of nicotine tested. Conclusions: These findings support the hypothesis that TPM is more reinforcing than nicotine alone. However, the increased reinforcing efficacy of TPM cannot be attributed to the actions of harman and norharman. The potential role of serotonin inhibition in tobacco reward processes is discussed.</p>

Contribution of Harman and Norharman to the Reinforcing Efficacy of Aqueous Tobacco Smoke Extract Self-Administered by Rats

<p>Background: Animal models of drug abuse treat nicotine as the primary reinforcing agent that promotes tobacco addiction. However, rodents demonstrate poor self-administration of nicotine despite evidence of tobacco's high abuse potential in humans. This discrepancy has been attributed to other constituents of tobacco smoke that facilitate the development of nicotine dependence. Objectives: This study aimed to determine whether rats would self-administer intravenous an aqueous tobacco smoke extract (TPM) to find evidence if it was more reinforcing than nicotine alone. The study also evaluated the role of tobacco smoke constituent’s harman and norharman in any differences observed. Methods: Firstly, male Sprague-Dawley rats (n=29) were assigned to treatment groups: nicotine (30.0μg/kg/infusion), TPM (containing 30.0μg/kg/infusion nicotine) or saline vehicle. Ability for each treatment to support intravenous self-administration was assessed using spontaneous acquisition of responding on gradually increasing fixed ratio schedules (FR1, FR2, FR5). Subsequent progressive ratio (PR) testing was employed to determine reinforcing efficacy of each treatment. Then a second group of rats (N = 56) were assigned to treatment groups: nicotine alone (30.0 or 75.0μg/kg/infusion) or nicotine combined with norharman (0, 0.4, 2.5 or 6.25μg/kg/infusion) and harman (0.0, 1.6 or 10.0μg/kg, IP), and tested using a similar protocol. Results: Animals readily acquired self-administration responding for TPM and produced higher PR breakpoints (BP) than rats treated with nicotine alone or vehicle. Rats trained to respond for a larger dose of nicotine demonstrated significantly greater response rates than those receiving the lower dose of nicotine. Finally, the addition of harman and norharman to nicotine significantly reduced BP at the lower unit dose of nicotine tested. Conclusions: These findings support the hypothesis that TPM is more reinforcing than nicotine alone. However, the increased reinforcing efficacy of TPM cannot be attributed to the actions of harman and norharman. The potential role of serotonin inhibition in tobacco reward processes is discussed.</p>

Assessment of the Reinforcing Properties of Orally Administered MDMA ('Ecstasy') in Rats

<p>The so-called “party drug” 3,4-Methylenedioxymethamphetamine (MDMA, or ecstasy) may share many of the addictive properties common to other CNS stimulants. In humans MDMA is primarily consumed orally in one more pills per session. However, animal research has mostly focused on examining the effects of MDMA as a function of other routes of administration. Route of administration can have profound effects on the subjective and reinforcing properties of drugs of abuse. This thesis assessed the locomotor-activating and reinforcing properties of MDMA when delivered orally. MDMA-induced hyperlocomotion was used to examine magnitude of response and onset of action as a function of ip, sc and oral administration. Significant route-dependant effects were found with ip producing higher locomotor activity than sc and oral respectively. Onset of action was slower for subcutaneous administration compared with both ip and oral administration. The reinforcing properties of MDMA were examined by use of the self-administration procedure. Oral MDMA self-administration was firstly examined using simple schedules of reinforcement as a function of two different vehicle substrates, water (under water deprivation) and saccharin. Oral MDMA maintained responding and reliable dose-response curves were obtained under both water and saccharin vehicle conditions. However, both saccharin and water vehicle conditions also acted as strong reinforcers in these studies. Further studies utilising a behavioural economic approach were conducted in order to delineate the reinforcing effects of MDMA from that of its parent vehicle. In addition, demand-curve analysis using both the Linear-Elasticity model (Hursh et al., 1988, 1989) and the Exponential Model of Demand (Hursh & Silberberg, 2008) were compared in order to evaluate each model and assess the relative reinforcing efficacy of oral MDMA. Demand curves for the oral self-administration of MDMA revealed that responding for MDMA was more elastic (lower Pmax) than responding for saccharin-alone indicating that saccharin functioned as stronger reinforcer than did MDMA+saccharin. The results of these studies provide evidence for the positive-reinforcing effects of MDMA when it is delivered via the oral route of administration, however, the relative reinforcing efficacy of orally delivered MDMA appears to be low.</p>

Assessment of the Reinforcing Properties of Orally Administered MDMA ('Ecstasy') in Rats

<p>The so-called “party drug” 3,4-Methylenedioxymethamphetamine (MDMA, or ecstasy) may share many of the addictive properties common to other CNS stimulants. In humans MDMA is primarily consumed orally in one more pills per session. However, animal research has mostly focused on examining the effects of MDMA as a function of other routes of administration. Route of administration can have profound effects on the subjective and reinforcing properties of drugs of abuse. This thesis assessed the locomotor-activating and reinforcing properties of MDMA when delivered orally. MDMA-induced hyperlocomotion was used to examine magnitude of response and onset of action as a function of ip, sc and oral administration. Significant route-dependant effects were found with ip producing higher locomotor activity than sc and oral respectively. Onset of action was slower for subcutaneous administration compared with both ip and oral administration. The reinforcing properties of MDMA were examined by use of the self-administration procedure. Oral MDMA self-administration was firstly examined using simple schedules of reinforcement as a function of two different vehicle substrates, water (under water deprivation) and saccharin. Oral MDMA maintained responding and reliable dose-response curves were obtained under both water and saccharin vehicle conditions. However, both saccharin and water vehicle conditions also acted as strong reinforcers in these studies. Further studies utilising a behavioural economic approach were conducted in order to delineate the reinforcing effects of MDMA from that of its parent vehicle. In addition, demand-curve analysis using both the Linear-Elasticity model (Hursh et al., 1988, 1989) and the Exponential Model of Demand (Hursh & Silberberg, 2008) were compared in order to evaluate each model and assess the relative reinforcing efficacy of oral MDMA. Demand curves for the oral self-administration of MDMA revealed that responding for MDMA was more elastic (lower Pmax) than responding for saccharin-alone indicating that saccharin functioned as stronger reinforcer than did MDMA+saccharin. The results of these studies provide evidence for the positive-reinforcing effects of MDMA when it is delivered via the oral route of administration, however, the relative reinforcing efficacy of orally delivered MDMA appears to be low.</p>