Avoiding costly mistakes in groups: The evolution of error management in collective decision making.

Individuals continuously have to balance the error costs of alternative decisions. A wealth of research has studied how single individuals navigate this, showing that individuals develop response biases to avoid the more costly error. We, however, know little about the dynamics in groups facing asymmetrical error costs and when social influence amplifies either safe or risky behavior. Here, we investigate this by modeling the decision process and information flow with a drift-diffusion model extended to the social domain. In the model individuals first gather independent personal information; they then enter a social phase in which they can either decide early based on personal information, or wait for additional social information. We combined the model with an evolutionary algorithm to derive adaptive behavior. We find that under asymmetric costs, individuals in large cooperative groups do not develop response biases because such biases amplify at the collective level, triggering false information cascades. Selfish individuals, however, undermine the group's performance for their own benefit by developing higher response biases and waiting for more information. Our results have implications for our understanding of the social dynamics in groups facing asymmetrical errors costs, such as animal groups evading predation or police officers holding a suspect at gunpoint.

[18F]fluorodeoxyglucose positron emission tomography scanning for staging, response assessment, and disease surveillance in patients with mantle cell lymphoma.

BACKGROUND: Positron emission tomography (PET) is an important imaging modality in the staging and response assessment of patients with lymphoma, but data on its specific use in mantle cell lymphoma (MCL) are lacking. PATIENTS AND METHODS: The records of 28 patients with MCL who had a total of 123 [18F]fluorodeoxyglucose (FDG) PET scans between March 1999 and November 2005 were reviewed. Nine patients had staging scans. The other scans were performed for response assessment or relapse surveillance. RESULTS: FDG-PET sensitivity was 100% for nodal disease in the 9 patients studied at baseline. Positron emission tomography scans performed for response assessment were concordant with conventional imaging in 47% and discordant in 53% of cases. Positron emission tomography scanning led to earlier diagnosis of relapse in 1 of 17 patients but produced a high rate of false-negative findings in the evaluation of gastrointestinal involvement. CONCLUSION: FDG-PET appears to be a sensitive modality for staging and for response assessment in MCL but was not found to be useful in relapse surveillance or in the evaluation of gastrointestinal disease.

Early therapeutic response assessment by (18)FDG-positron emission tomography during chemotherapy in patients with diffuse large B-cell lymphoma: isolated residual positivity involving bone is not usually a predictor of subsequent treatment failure.

Residual 2-fluoro-2-deoxyglucose (FDG) - positron emission tomography (PET) positivity during treatment of patients with diffuse large B-cell lymphoma (DLBLC) prospectively identifies a subgroup at high likelihood of subsequent treatment failure. A single institution clinical audit of FDG-PET performance for this indication was undertaken for patients with DLBCL treated with anthracycline-based chemotherapy +/- radiotherapy. Of 45 eligible patients, 14 (31%) were PET-positive after a median of three chemotherapy cycles (range 1 - 5), of which 10 (71%) progressed at a median of 6.5 months. An interim positive PET was a statistically significant adverse prognostic factor for treatment failure (P < 0.0001, log-rank analysis) with a hazard ratio for a positive interim-treatment PET of 9 (95% confidence interval = 4 - 55) and positive predictive value of 71% and negative predictive value of 90%. Notably, four patients with low-grade FDG-avidity limited to sites previously involved by biopsy-proven osseous lymphoma, remain progression-free (median follow-up 62 months). Low-grade FDG-avidity on interim restaging at sites of bone involvement by DLBCL at diagnosis, appears to be less predictive of disease progression than residual nodal or extra-nodal soft tissue abnormality by PET.