Gambling Research Group Publications


Robert  Baker

Marshall, D., & Baker, R. (2001) Unfair odds? Factors influencing the distribution of electronic gaming machines in Melbourne. Urban Policy and Research, 19, 77–92.

Since the rapid proliferation of electronic gaming machines in Australia during the 1990s, it has been recognised that regions of lower socioeconomic status have experienced the greatest allocations of these machines. It has generally been argued that market forces are the main reason for this. This paper, addressing the case study of Melbourne, suggests that legislative, historical and cultural factors, among others, might also underpin and re-enforce the emergent spatial inequities.


Marshall, D., Baker, R. G. V. (2002). The Evolving Market Structures of Gambling: Case Studies Modelling the Socioeconomic Assignment of Gaming Machines in Melbourne and Sydney, Australia. Journal of Gambling  Studies, 18, 273–291.

The expansion of gambling industries worldwide is intertwined with the growing government dependence on gambling revenue for fiscal assignments. In Australia, electronic gaming machines (EGMs) have dominated recent gambling industry growth. As EGMs have proliferated, growing recognition has emerged that EGM distribution closely reflects levels of socioeconomic disadvantage. More machines are located in less advantaged regions. This paper analyses time-series socioeconomic distributions of EGMs in Melbourne, Australia, an immature EGM market, and then compares the findings with the mature market in Sydney. Similar findings in both cities suggest that market assignment of EGMs transcends differences in historical and legislative environments. This indicates that similar underlying structures are evident in both markets. Modelling the spatial structures of gambling markets provides an opportunity to identify regions most at risk of gambling related problems. Subsequently, policies can be formulated which ensure fiscal revenue from gambling can be better targeted towards regions likely to be most afflicted by excessive gambling-related problems.


Baker, R. G. V., & Marshall, D. C. (2005). Modelling gambling time and economic assignments to weekly trip behavior to gambling venues. Journal of Geographical Systems, 7, 381–402.

The study of gambling and its socio-economic structures should be an area of growing interest to a society-relevant geography. In Australia, electronic gaming machines (EGMs) have dominated recent gambling industry growth. As EGMs have diffused through the urban hierarchy, there is a growing recognition that EGM distribution often correlates with levels of socio-economic status. Marshall and Baker (2002) showed that a similar EGM socio-economic assignment model evolved in the capital cities of Sydney and Melbourne, Australia, even though these cities have substantially different historical and legislative EGM environments. This paper looks at a related space–time model in the context of trip-making to gaming venues, relative to an Index of Economic Resources from the Australian Bureau of Statistics. A simulation of the model predicts different types of gambling behaviour. It also shows that venue hours can affect time–economic trip behaviour. The model is then applied to EGM gambling data gathered in an urban hierarchy on the north coast of New South Wales,
Australia. The results define a gaussian-type low involvement ‘recreational random’ gambling for patrons, whereas for more involved gamblers (in terms of time spent gambling), there are discrete behavioural periods over the week for a wider economic cohort. This leads to the possibility of a spectrum of time–economic EGM gambling assignments for participating households in metropolitan and non-metropolitan areas.


Barry Tolchard

Tolchard, B., Glozah, F. & Pevalin, D. (2014). Attitudes to gambling in Ghanian adolescents. Journal of Addiction & Research, 5.

Gambling is on the rise throughout the world. Gambling operators are seeing new opportunities to introduce their products into less developed areas. Ghana has recently legalized gambling, giving residents the chance to play both online and with land based providers. There has been limited research into the impacts of legalizing gambling in Ghana, with no social impact or attitudinal data available. This paper will describe the first study to examine the attitudes to gambling of Ghanaian adolescents and the impact this may be having on their school attainment and mental well-being. A series of gambling attitudinal questions were asked of 693 adolescent alongside perceived social support and stress factors in relation to their educational attainment.
The results indicate there is a strong view that Ghanaian adolescents consider gambling to be a positive experience and a possible way out of poverty. However, adolescents with strong positive attitudes to gambling experienced poor social support
and high levels of stress, impacting on their overall education. The study concludes better gambling education is need in Ghanaian schools.


Hing, N., Russell, A., Tolchard, B., & Nower, L. (2014). A comparative study of men and women gamblers in Victoria: Victorian Responsible Gambling Foundation.

Research Objectives

This study was funded by the Victorian Responsible Gambling Foundation to extend the analyses conducted for A Study of Gambling in Victoria (Hare, 2009) to provide detailed analyses of similarities and differences between male and female gamblers in Victoria Australia. The research objectives were to:

  1. Analyse the similarities and differences between male and female gamblers in Victoria in terms of gambling preferences, activities and styles of play; gambling motivations and attitudes; physical and mental health; family and early gambling influences; and help-seeking behaviour; and
  2. Analyse the similarities and differences between male and female gamblers in Victoria in terms of risk factors associated with problem/moderate risk gambling and protective factors associated with low risk/non-problem gambling.

Battersby, M. W., Thomas, L. J., Tolchard, B., & Esterman, A. (2002). The South Oaks Gambling Screen: A Reviews with Reference to Australian Use. Journal of Gambling Studies, 18, 257–271.

The South Oaks Gambling Screen (SOGS) is a psychometric instrument widely used internationally to assess the presence of pathological gambling. Developed by Lesieur and Blume (1987) in the United States of America (USA) as a self-rated screening instrument, it is based on DSM-III and DSM-III-R criteria. This paper describes the origins and psychometric development of the SOGS and comments critically in relation to its construct validity and cutoff scores. Reference is made to the use of the SOGS in the Australian setting, where historically gambling has been a widely accepted part of the culture, corresponding to one of the highest rates of legalised gambling and gambling expenditure in the world. An alternative approach to the development of an instrument to detect people who have problems in relation to gambling is proposed.


Battersby, M., Tolchard, B., Scurrah, M., & Thomas, L. (2006). Suicide Ideation and Behaviour in People with Pathological Gambling Attending a Treatment Service. International Journal of Mental Health  Addiction, 4, 233–246.

This study aimed to describe the 12-month period prevalence and risk factors for suicidal ideation and behaviour in a cohort of patients with pathological gambling attending a treatment service. Seventy-nine people with a diagnosis of pathological gambling received a mail out survey that included questions on postulated risk factors for suicidal ideation and behaviour, the modified Suicide Ideation Scale (SIS), the South Oaks Gambling Screen (SOGS), the Beck Depression Inventory (BDI) and the CAGE. A total of 54.4% of the surveys were returned completed. There were 81.4% who showed some suicidal ideation and 30.2% reported one or more suicide attempts in the preceding 12 months. Suicidal ideation and behaviours were positively correlated with the gambling severity (SOGS scores), the presence of debt attributed to gambling, alcohol dependence and depression (BDI). Suicidal ideation/behaviour was not significantly associated with gender and living arrangements, nor a history of receiving treatment for depression during the preceding 12 months. People with pathological gambling attending a treatment service had higher levels of suicidal ideation and behaviour than previous studies. Pathological gambling should be seen as a chronic condition with a similar risk for suicidal ideation and behaviour as other mental illnesses. Counselling services, general practitioners and mental health services should screen for gambling problems when assessing risk after suicide attempts and for suicide risk in patients presenting with gambling problems and co morbid depression, alcohol abuse and a previous suicide attempt.


Hing, N., Nuske, E., Tolchard, B., & Russell, A. (2014). What influences the types of help that problem gamblers choose? A preliminary grounded theory model. International. Journal of Mental Health  & Addiction.

Research has not fully explored factors that influence types of help used from the suite of available options once problem gamblers reach an action stage of change. This study aimed to explore critical factors influencing choice of help (or interventions) once people have decided to address their gambling problem. Particular emphasis was on counselling and self-exclusion, given their demonstrable effectiveness for most users. Interviews were conducted with 103 problem gamblers taking action to address their gambling problem. Inductive analysis revealed nine critical influences on type(s) of help chosen, presented as a grounded theory model.

Independent variables were goals of taking up the intervention, problem gambling severity, and level of independence/pride. Six mediating variables helped to explain relationships between the independent variables and choice of intervention. Understanding key influences on choice of gambling help can illuminate how to encourage further uptake and better align interventions with gamblers’ preferences, to reduce barriers to help-seeking.


Tolchard, B. (2015). The impact of gambling on rural communities worldwide: A narrative literature review. Journal of Rural  Mental Health.

Gambling has become a popular activity in both urban and rural settings. Although the prevalence and participation of gambling is well known, little has been reported regarding the impacts of gambling on rural communities. Therefore, a narrative literature review approach was adopted to examine what is known regarding gambling in rural communities. This article describes the prevalence and types of gambling that are popular in rural communities around the world. It identifies the benefits and highlights the potential harm caused by a person’s gambling and the impact this has on families and the wider rural community. There are both benefits and risks associated with increased availability of gambling opportunities. Specific vulnerable groups within rural populations are identified within this context and how different countries respond to rural gambling is explored. A number of strategies based on a public health approach are recommended to ensure that gambling remains as harmless an activity as possible in rural communities.


Tolchard, B., Delfabbro, P. (2013). The Victorian Gambling Screen:Validity and Reliability in an Adolescent Population. International  Journal of Mental Health & Addiction.

Although many attempts have been made to assess problem or pathological gambling in adolescents, concerns have been raised about whether existing measures are ideally suited for this purpose. Such measures are heavily influenced by traditional addiction models common to the study of substance use. In contrast, more recent public health approaches to gambling place a greater emphasis on the role of behavior and its harmful consequences and this is implicit in many currently accepted definitions of problem gambling. This paper reports on the use of one such measure (Victorian Gambling Screen -VGS), with 926 grade 7–12 adolescents surveyed in the Australian Capital Territory. The VGS was shown to correlate well with the gold standard Diagnostic & Statistical Manual-IV-Juvenile Screen (DSM-IV-J) for problem gamblers producing similar prevalence estimates. The measure also has sound internal reliability and concurrent validity. The findings suggest that harm-based measures such as the VGS are credible with adolescent populations in Australia and that various forms of harm observed in adult populations can also be observed in adolescent problem gamblers.


Hing, N., Russell, A., Tolchard, B. (2015). Are There Distinctive Outcomes from Self-Exclusion? An Exploratory Study Comparing Gamblers Who Have Self-Excluded, Received Counselling, or Both. International Journal of Mental Health and Addiction.

Research has not determined whether typical improvements in psychosocial functioning following self-exclusion are due to the intervention. This study aimed to explore distinctive outcomes from self-exclusion by assessing outcomes between 1) self-excluders who had and had not received gambling counselling and 2) self excluders compared to non-self-excluders who had received gambling counselling. A longitudinal design administered three assessments on gambling behaviour, problem gambling severity, gambling urge, alcoholism, general health, and harmful consequences. Of the 86 participants at Time 1 with similar baseline scores, 59.3% completed all assessments. By Time 2, all groups (self-excluded only, self-excluded plus counselling, counselling only) had vastly improved on most outcome measures. Improvements were sustained at Time 3. Outcomes did not differ for self-exclusion combined with counselling. Compared to non-excluders, more self-excluders abstained from most problematic gambling form and fewer had harmful consequences. Findings suggest self-exclusion may have similar short-term outcomes to counselling alone and may reduce harm in the short-term.


Hing, N., Russell, A., Tolchard, B., & Nower, L. (2015, online). Risk factors for gambling problems: An analysis by gender. Journal of Gambling Studies.

Differences in problem gambling rates between males and females suggest that associated risk factors vary by gender. Previous combined analyses of male and female gambling may have obscured these distinctions. This study aimed to develop separate risk factor models for gambling problems for males and for females, and identify gender-based similarities and differences. It analysed data from the largest prevalence study in Victoria Australia (N = 15,000). Analyses determined factors differentiating non-problem from at-risk gamblers separately for women and men, then compared genders using interaction terms. Separate multivariate analyses determined significant results when controlling for all others. Variables included demographics, gambling behaviour, gambling motivations, money management, and mental and physical health. Significant predictors of at-risk status amongst female
gamblers included: 18-24 years old, not speaking English at home, living in a group household, unemployed or not in the workforce, gambling on private betting, electronic gaming machines (EGMs), scratch tickets or bingo, and gambling for reasons other than social reasons, to win money or for general entertainment. For males, risk factors included: 18-24 years old, not speaking English at home, low education, living in a group household, unemployed or not in the workforce, gambling on EGMs, table games, races, sports or lotteries, and gambling for reasons other than social reasons, to win money or for general entertainment. High risk groups requiring appropriate interventions comprise young adults, especially males; middle-aged female EGM gamblers; non-English speaking populations; frequent EGM, table games, race and sports gamblers; and gamblers motivated by escape.


Tolchard, B. (2013). Measurement Issues in Problem Gambling: Inclusion of a Gambling Specific Psychopathology Measure, the Gambling Impact Scale (GIS). Psychology and Social Behaviour Research, 1, 52–55.

Problem gambling is becoming an increasing issue throughout the world with greater numbers of people presenting to treatment services with gambling problems. However, many cases are still missed, due in part, to a lack of general screening tools that are able to be used by non-specialist gambling services. This paper presents the findings of a gambling screening tool (Gambling Impact Scale — GIS) which was designed to identify problem gambling behavior, associated psychopathology and impact to self and others. The principle aim was to devise a tool that could be used by all potential treatment agencies that may come into contact with people experiencing problems with their gambling. The GIS consists of three sub-scales. Both internal and concurrent validity of the tool have been established with a help seeking gambling population. Discussed are further refinements of the GIS in general mental health and counseling populations.


Tolchard, B., & Battersby, M. W. (2010). The Victorian Gambling Screen: Reliability and Validation in a Clinical Population. Journal  of Gambling Studies, 26, 623–638.

There is a need to establish reliability and the various forms of validity in all measures in order to feel confident in the use of such tools across a wide diversity of settings.

The aim of this study is to describe the reliability and validity of the Victorian Gambling Screen (VGS) and in particular one of the sub-scales (Harm to Self—HS) in a specialist problem gambling treatment service in Adelaide, Australia. Sixty-seven consecutive gamblers were assessed using a previously validated clinical interview and the VGS (Ben-Tovim et al., The Victorian Gambling Screen: project report. Victorian Research Panel, Melbourne, 2001). The internal consistency of the combined VGS scales had a Cronbach’s alpha of .85 with the HS scale .89. There was satisfactory evidence of convergent validity which included moderate correlations with another measure of gambling—the South Oaks Gambling Screen. There were also moderate correlations with other measures of psychopathology. Finally, how the VGS may best be used in clinical settings is discussed.


Tolchard, B., & Battersby, M. W. (2013). Cognitive Behaviour Therapy for Problem Gamblers: A Clinical Outcomes Evaluation. Behaviour  Change, 30, 12–23.

Cognitive-Behaviour Therapy (CBT) is considered the number one nonpharmacological treatment for a number of mental and psychological disorders (Tolin, 2010; Stuhlmiller & Tolchard, 2009). While CBT with problem gamblers has shown promise, the quality of the research in this area is lacking. One area of concern is that across the many trials and reports using CBT with gamblers no single unified approach has been used and so comparison across studies is limited. Similarly, translation of the CBT research into clinical practice is almost entirely absent (Walker, 2005). This article will explore the concepts of CBT with problem gamblers and identify common elements across all reported approaches. A unified model of CBT with problem gamblers will be suggested and the direct clinical application of this model described from a state-wide gambling service in Australia (Flinders Approach) with 205 problem gamblers. The results indicate that the Flinders Approach is successful in treating gamblers considered to be at the severest end of the experience, with a 69% completion rate. Implications for future research in which this model may be tested against other therapies and pharmacological treatments will be discussed.


Tolchard, B., Thomas, L., & Battersby, M. (2006). Single-Session Exposure Therapy for Problem Gambling: A Single-Case Experimental Design. Behaviour Change, 23, 148–155.

There is a paucity of treatment-outcome research for problem gambling or pathological gambling. Single-session exposure therapy has been used successfully with a broad range of psychological disorders such as panic disorder ad phobias. This article will describe the use of single-session graded exposure to treat problem gambling with an Electronic Gaming Machine (EGM) gambler. Pretreatment to 6-month follow-up repeated measures showed a significant reduction in client-rated gambling severity, that is, showed a significant reduction in client-rated gambling severity (Gambling Severity Checklist [GSCL]), the Symptom Chechklist-90-Revised (SCL-90-R) and the Beck Depression Inventory (BDI). This case demonstrates a novel intervention which is brief, convenient and accessible to the client, and which resulted in gains maintained over the medium-term. This promising single case indicates the need for further research to determine whether positive benefits are realized in larger randomized control designs.


Tolchard, B., Thomas, L., & Battersby, M. (2007). GPs and Problem Gambling: Can they Help with Identification and Early Intervention?. Journal of Gambling Studies, 23, 499–506.

General Practitioners (GPs) are well placed to identify problem gamblers and provide early intervention. To date there is no evidence to suggest that GP’s are routinely screening patients for potential gambling problems. This paper discusses the prevalence of problem gambling, the links with other health problems and ways that GPs can assist. Results from a pilot project that provided educational resources to GPS are also discussed. Suitable screening tools are available that could easily be used by GPs to assess the possibility of gambling problems in patients who may be at increased risk but do not seek help. Early identification and intervention may help prevent a gambling habit escalating to a serious problem. More work needs to be done to increase awareness with GPs of the extent of problem gambling in our community and to alert patients to the fact that gambling can affect their health and that GPs can help.


Lewis Bizo

Armour, R. A., & Bizo, L. A. (2014). Modeling gambling: An Application of the Mathematical Principles of Reinforcement. Analysis  of Gambling Behaviour, 8, 23–37.

The Mathematical Principles of Reinforcement  (MPR ) has proved a useful model for predicting and describing the behaviour of non-human animals on different schedules of reinforcement. This research tests the ability of MPR to accurately predict performance of adult humans on a simulated gambling task. A simulated electronic gaming machine was used in three experiments and gambling responses were reinforced according to series of Random Ratio schedules. In Experiment 1, when participants experienced either an ascending or descending order of ratios, rates of responding were well described by a bitonic response gradient. In Experiments
2 and 3 participants experienced either an early large win or an early large loss before experiencing a series of ratio schedule values that were presented in ascending order. Again rates of responding, expressed as a function of ratio schedule value, were well described by a bitonic response gradient. The early large loss condition produced higher response rates than the early large win condition. The bitonic response gradients of all conditions were well described by MPR via changes in the parameter a, specific activation.


Strickland, C. J. R., Taylor, A., Hendon, K. J., Provost, S. C., & Bizo, L. A. (2006). Erroneous beliefs among frequent fruit-machine gamblers. Gambling Research, 18(2), 42.

The present studies investigated the extent to which fruit-machine gamblers held erroneous beliefs, specifically the illusion of control and gambler's fallacy. In Study 1, 9 participants were interviewed and their audiotaped responses submitted to a thematic analysis, which suggested that the 4 frequent gamblers were more likely to express beliefs and statements consistent with the cognitive biases of illusion of control and the gambler's fallacy than the 5 infrequent gamblers. This observation was confirmed in the second study when the Gamblers' Beliefs Questionnaire (GBQ) was completed by 37 participants (10 frequent gamblers, 11 infrequent gamblers and 16 non-gamblers). Frequent fruit machine gamblers were more inclined than infrequent fruit machine gamblers to express beliefs consistent with the cognitive biases, the illusion of control and the gambler's fallacy.


Anne Macaskill

Tan, G., Macaskill, A. C., Harper, D. N., & Hunt, M. J. (2015). Derived relations and the slot machine near-win effect. European Journal of Behavior Analysis, 1–10.

The current study investigated whether verbal processes underlie preferences for slot machines that present near-win outcomes. Near wins are loss outcomes that resemble wins. Participants completed a relational training task. For one group, near wins were related to the word “loss”. For the other group, near wins were related to the word “almost”. Participants rated how “like a win” near-win outcomes were before and after completing this relational training task. They also made repeated choices between a simulated slot machine that presented near wins and one that did not. Participants who acquired derived relations between near-win outcomes and “loss” showed a reduction in the near-win effect on both preference and verbal ratings. These results suggest that verbal processes may contribute to preferences for slot machines that present near-win outcomes.


Daly, T. E., Tan, G., Hely, L. S., Macaskill, A. C., Harper, D. N., & Hunt, M. J. (2014). Slot Machine Near Wins: Effects on Pause and Sensitivity to Win Ratios. Analysis of Gambling Behavior 8, 55–70.

When a near-win outcome occurs on a slot machine, stimuli presented resemble those presented when money is won, but no money is won. Research has shown that gamblers prefer and play for longer on slot machines that present near wins. One explanation for this is that near wins are conditioned reinforcers. If so, near wins would produce longer latencies to the next response than clear losses. Another explanation is that near wins produce frustration; if so, then near wins would produce shorter response latencies. The two current experiments manipulated win ratio across two concurrently available slot machines and also manipulated near win frequency. Latencies were longer following near wins, consistent with near wins functioning as conditioned reinforcers. We also explored the effects of near wins on sensitivity to relative win rate and found that higher rates of near wins were associated with greater sensitivity to relative win frequency, an effect also consistent with near wins as conditioned reinforcers.


Mackaskill, A. C., & Hackenberg, T. D. (2013). Optimal and nonoptimal choice in a laboratory-based sunk cost task with humans: A cross-species replication. Journal of the experimental analysis of  behavior, 100, 301–315.

The current four experiments examined the sunk cost effect—nonoptimal persistence following investment—in a laboratory-based decision-making task with adult humans. Subjects made repeated decisions about whether to persist in a course of action—a fixed-ratio schedule whose response requirements varied unpredictably from one trial to the next—or to abandon it and escape in favor of a new trial with a potentially smaller fixed ratio schedule. Satisfying the ratio requirement produced a brief video clip from a preferred television program. In Experiment 1, sunk-cost errors were less likely in subjects who had previously experienced markedly differential reinforcement for escape. In Experiment 2, stimulus changes correlated with changes in mean response requirement, and these changes reduced sunk-cost errors in a small number of subjects. In Experiment 3, sunk-cost errors occurred more frequently as the ratio of the mean response requirements for persistence and escape approached 1.0. The importance of this variable was further supported by the results of Experiment 4, in which features other than this ratio did not markedly alter performance. These four experiments identified some key determinants of whether humans commit the sunk-cost error and confirmed the utility of video clips as reinforcers in experimental research with humans


Mackaskill, A. C., Hackenberg, T. D. (2012). Providing a reinforcement history that reduces the sunk cost effect. Behavioural  Processes, 89, 212–218.

The sunk cost error occurs when individuals persist with a non-optimal course of action because they have already invested time or resources in it. The current study examined the effect of specific experiences on the likelihood of the sunk cost error. Six pigeons were given repeated choices between persisting with and escaping from relatively large fixed ratios. In most conditions escaping was the choice pattern producing the smallest mean response requirement. In Experiment 1, four of six pigeons persisted, committing the sunk cost error. Some subjects continued to persist even when persistence increased the mean number of responses to reinforcement by 99. In Experiment 2, the absolute difference between the mean numbers of responses to reinforcement for persistence and escape was increased even further for these subjects, and the relative cost of persistence was increased. Once escape had been established, pigeons were less likely to commit the sunk cost error in some conditions where they had previously made the error frequently. Together, the results of both experiments show changes in the frequency of the sunk cost error caused by specific experiences, and that persistence is likely more sensitive to its relative than absolute costs.


Mackaskill, A. C., & Branch, M. N. (2012). Tolerance to cocaine’s effects on schedule-controlled behavior: Role of delay between pause-ending responses and reinforcement. Pharmacology Biochemistry  and Behaviour, 100, 616–623.

The schedule of reinforcement under which behavior is maintained is an important contributor to whether tolerance to the behavioral effects of cocaine develops. Schedule parameter value (for example, fixed-ratio size) has been shown to affect the development of tolerance under some schedule types but not others, but the specific procedural variables causing this effect remain to be identified. To date, schedule-parameter-related tolerance has developed when a longer pause after reinforcement does not lead to a shorter delay between the response that ends the pause and reinforcement. The current study investigated the importance of this variable in pigeons using a multiple chained Fixed-Ratio 1, Fixed-Time x schedule, in which the first key peck in a trial produced a stimulus change and initiated a delay at the end of which food was presented regardless of whether or not additional pecks were made during the delay. Dose–response curves were assessed before, during and after chronic (daily) administration of cocaine. Tolerance to the pause-increasing effects of cocaine occurred to a similar degree regardless of the scheduled time between the end of the pause and reinforcement. Therefore, the relationship between pause length and delay to reinforcement does not provide an explanation for schedule-parameter-related tolerance.


Mackaskill, A. C., & Hackenberg, T. D. (2012). The sunk cost effect with pigeons: some determinants of decisions about persistence. Journal of the experimental analysis of behavior, 97, 85–100.

The sunk cost effect occurs when an individual persists following an initial investment, even when persisting is costly in the long run. The current study used a laboratory model of the sunk cost effect. Two response alternatives were available: Pigeons could persist by responding on a schedule key with mixed ratio requirements, or escape by responding on a second key. In Experiment 1, mean response requirements for persistence and escape were varied across conditions. Pigeons persisted (committing the sunk cost error) when persisting increased the mean response requirement only slightly but not when persisting was sufficiently nonoptimal. Experiment 2 explored more systematically combinations of ratios and probabilities assigned to the schedule key. Persistence varied with the ratio of the mean global response requirements for persistence and escape. In Experiment 3, transitions between ratios were signaled. This reduced nonoptimal persistence, and produced some instances of a reverse sunk cost error—escaping when persistence was optimal. In Experiment 4, it was optimal to escape after the second-smallest ratio ever presented. Pigeons escaped at approximately the optimal juncture, especially in conditions with added signals. Overall, this series of experiments suggests that the sunk cost error may arise in part because persistence is the default behavioral strategy in situations where the contingencies for escape and persistence are insufficiently disparate and/or it is relatively difficult to discriminate when to escape. The study also demonstrates the utility of animal models of complex decision making situations.


Adam Rock and Gavin Clark

Tricker, C., Rock, A. J., & Clark, G. I. (2015). Cue-Reactive Altered State of Consciousness Mediates the Relationship Between Problem-Gambling Severity and Cue-Reactive Urge in Poker-Machine Gamblers. Journal of Gambling Studies.

In order to enhance our understanding of the nature of poker-machine problem-gambling, a community sample of 37 poker-machine gamblers (Mage = 32 years, MPGSI = 5; PGSI = Problem Gambling Severity Index) were assessed for urge to gamble (responses on a visual analogue scale) and altered state of consciousness (assessed by the Altered State of Awareness dimension of the Phenomenology of Consciousness Inventory) at baseline, after a neutral cue, and after a gambling cue. It was found that (a) problem-gambling severity (PGSI score) predicted increase in urge (from neutral cue to gambling cue, controlling for baseline; sr2 = .19, p = .006) and increase in altered state of consciousness (from neutral cue to gambling cue, controlling for baseline; sr2 = .57, p\.001), and (b) increase in altered state of consciousness (from neutral cue to gambling cue) mediated the relationship between problem-gambling severity and increase in urge (from neutral cue to gambling cue; j2 = .40, 99 % CI [.08, .71]). These findings suggest that cue-reactive altered state of consciousness is an important component of cue-reactive urge in poker-machine problem-gamblers.