PsycINFO classification: 2340

Abstract Orthodox game theory and social preference models cannot explain why people cooperate in many experimental games or how they manage to coordinate their choices. The theory of evidential decision making provides a solution, based on the idea that people tend to project their own choices onto others, whatever these choices might be. Evidential decision making preserves methodological individualism, and it works without recourse to social preferences. Rejecting methodological individualism, team reasoning is a thinly disguised resurgence of the group mind fallacy, and the experiments reported by Colman et al

Game interrupted: The rationality of considering the future

The “problem of points”, introduced by Paccioli in 1494 and solved by Pascal and Fermat 160 years later, inspired the modern concept of probability. Incidentally, the problem also shows that rational decision-making requires the consideration of future events. We show that naïve responses to the problem of points are more future oriented and thus more rational in this sense when the problem itself is presented in a future frame instead of the canonical past frame. A simple nudge is sufficient to make decisions more rational. We consider the implications of this finding for hypothesis testing and predictions of replicability

Attribution and Categorization Effects in the Representation of Gender Stereotypes

Social stereotypes involve judgments of how typical certain personality traits are of a group. According to the attribution hypothesis, judgments of trait typicality depend on the perceived prevalence of the trait in the target group. According to the categorization hypothesis, such judgments depend on the degree to which a trait is thought to be more or less prevalent in the target group than in a relevant comparison group. A study conducted with women and men as target groups showed that the attribution hypothesis fit the data best when typicality ratings were made in an absolute format. When, however, typicality ratings were made in a comparative format (how typical is the trait of women as compared with men?), both hypotheses received support. Analytical derivation, supported by empirical evidence, showed an inverse relationship between the size of perceived group differences and their weight given in stereotyping. Implications for stereotype measurement and the rationality of social perception are discussed

Outcomes and expectations in dilemmas of trust

Rational trust decisions depend on potential outcomes and expectations of reciprocity. In the trust game, outcomes and expectations correspond to the structural factors of risk and temptation. Two experiments investigated how risk and temptation influenced information search and final decisions in the trust game. The central finding was that trustors underemphasized temptation relative to its effects on the expected value of trust. Instead, trustors made decisions egocentrically, focusing on potential outcomes. In Experiment 1, information search data revealed that trustors often made decisions without learning about the payoffs related to temptation. Experiment 2 investigated whether trustors were able to use temptation to form accurate expectations of reciprocity. Trustors understood, but underestimated, the relationship between temptation and the probability of reciprocity. Moreover, they did not fully consider expectations in their final trust decisions. Changes in potential outcomes had larger effects on trust than comparable changes in expectations. These results suggest that levels of trust are too high when the probability of reciprocity is low and too low when that probability is high

Deciding what to replicate: a formal definition of “replication value” and a decision model for replication study selection

Multivariate analysis of psychological dat

Oral abstracts 1: SpondyloarthropathiesO1. Detecting axial spondyloarthritis amongst primary care back pain referrals

Background: Inflammatory back pain (IBP) is an early feature of ankylosing spondylitis (AS) and its detection offers the prospect of early diagnosis of AS. However, since back pain is very common but only a very small minority of back pain sufferers have ASpA or AS, screening of back pain sufferers for AS is problematic. In early disease radiographs are often normal so that fulfilment of diagnostic criteria for AS is impossible though a diagnosis of axial SpA can be made if MRI evidence of sacroiliitis is present. This pilot study was designed to indicate whether a cost-effective pick up rate for ASpA/early AS could be achieved by identifying adults with IBP stratified on the basis of age. Methods: Patients aged between 18 and 45 years who were referred to a hospital physiotherapy service with back pain of more than 3 months duration were assessed for IBP. All were asked to complete a questionnaire based on the Berlin IBP criteria. Those who fulfilled IBP criteria were also asked to complete a second short questionnaire enquiring about SpA comorbidities, to have a blood test for HLA-B27 and CRP level and to undergo an MRI scan of the sacroiliac joints. This was a limited scan, using STIR, diffusion-weighted, T1 and T2 sequences of the sacroiliac joints to minimize time in the scanner and cost. The study was funded by a research grant from Abbott Laboratories Ltd. Results: 50 sequential patients agreed to participate in the study and completed the IBP questionnaire. Of these 27 (54%) fulfilled criteria for IBP. Of these, 2 patients reported a history of an SpA comorbidity - 1 psoriasis; 1 ulcerative colitis - and 3 reported a family history of an SpA comorbidity - 2 psoriasis; 1 Crohn's disease. 4 were HLA-B27 positive, though results were not available for 7. Two patients had marginally raised CRP levels (6, 10 -NR ≤ 5). 19 agreed to undergo MRI scanning of the sacroiliac joints and lumbar spine; 4 scans were abnormal, showing evidence of bilateral sacroiliitis on STIR sequences. In all cases the changes met ASAS criteria but were limited. Of these 4 patients 3 were HLA-B27 positive but none gave a personal or family history of an SpA-associated comorbidity and all had normal CRP levels. Conclusions: This was a pilot study yielding only limited conclusions. However, it is clear that: Screening of patients referred for physiotherapy for IBP is straightforward, inexpensive and quick. It appears that IBP is more prevalent in young adults than overall population data suggest so that targeting this population may be efficient. IBP questionnaires could be administered routinely during a physiotherapy assessment. HLA-B27 testing in this group of patients with IBP is a suitable screening tool. The sacroiliac joint changes identified were mild and their prognostic significance is not yet clear so that the value of early screening needs further evaluation. Disclosure statement: C.H. received research funding for this study from Abbott. A.K. received research funding for this study, and speaker and consultancy fees, from Abbott. All other authors have declared no conflicts of interes