In many intellective tasks groups consistently outperform individuals. One factor is that the individual(s) with the best answer is able to convince the other group members using sound argumentation. Another factor is that the most confident group member imposes her answer whether it is right or wrong. In Experiments 1 and 2, individual participants were given arguments against their answer in intellective tasks. Demonstrating sound argumentative competence, many participants changed their minds to adopt the correct answer, even though the arguments had no confidence markers, and barely any participants changed their minds to adopt an incorrect answer. Confidence could not explain who changed their mind, as the least confident participants were as likely to change their minds as the most confident. In Experiments 3 (adults) and 4 (10-year-olds), participants solved intellective tasks individually and then in groups, before solving transfer problems individually. Demonstrating again sound argumentative competence, participants adopted the correct answer when it was present in the group, and many succeeded in transferring this understanding to novel problems. Moreover, the group member with the right answer nearly always managed to convince the group even when she was not the most confident. These results show that argument quality can overcome confidence among the factors influencing the discussion of intellective tasks. Explanations for apparent exceptions are discussed.

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Can our knowledge about apples, cars, or smurfs hinder our ability to solve mathematical problems involving these entities? We argue that such daily-life knowledge interferes with arithmetic word problem solving, to the extent that experts can be led to failure in problems involving trivial mathematical notions. We created problems evoking different aspects of our non-mathematical, general knowledge. They were solvable by one single subtraction involving small quantities, such as 14-2 = 12. A first experiment studied how university-educated adults dealt with seemingly simple arithmetic problems evoking knowledge that was either congruent or incongruent with the problems' solving procedure. Results showed that in the latter case, the proportion of participants incorrectly deeming the problems "unsolvable" increased significantly, as did response times for correct answers. A second experiment showed that expert mathematicians were also subject to this bias. These results demonstrate that irrelevant non-mathematical knowledge interferes with the identification of basic, single-step solutions to arithmetic word problems, even among experts who have supposedly mastered abstract, context-independent reasoning.

The Attachment Multiple Model Interview (AMMI) was developed to assess internal working models (IWMs) of specific relationships in adulthood (e.g., with mother, father, and romantic partner). In an initial effort to validate the AMMI, the interview was administered to participants who were followed from age 4 to 23. ANOVA and contrast tests confirmed the AMMI's capacity to discriminate between mother, father, and partner IWMs. AMMI security with each parent was correlated with coherence according to the Adult Attachment Interview, and AMMI disorganization with mother with unresolved trauma (N = 53). AMMI dimensions of security, deactivation, and hyperactivation with the mother were associated with cumulative lifetime scores of security (N = 23), avoidance, and resistance (N = 34), respectively. Intercorrelations between these AMMI scales were also theory-consistent. Associations with the AAI and between AMMI security scores of different relationships are consistent with previous findings suggesting a contribution from both parents in the development of a state of mind, but a more important role of the mother for representations of the partner.

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