Dynamics of spontaneous thoughts: Exploration, attentional profile and the segmentation of the stream of thoughts.

For a long time, clinical knowledge and first-person reports have pointed to individual differences in the dynamics of spontaneous thoughts, in particular in the extreme case of psychiatric conditions (e.g. racing thoughts in Attention Deficit / Hyperactivity Disorder, ADHD; rumination in depression). We used a novel procedure to investigate this individual variability by combining verbal fluency tasks and introspective reports of thought content. Our goal was twofold. First, we tested the hypothesis that a greater segmentation of the stream of thoughts would be associated with trait inattention, in line with subjective reports of ADHD patients. Second, we tested whether the segmentation of the stream of thoughts increased with an increased tendency for exploratory behavior, following recent theoretical claims on the mechanisms underpinning the generation of spontaneous thoughts. Our results support both hypotheses, shedding light on the factors contributing to the individual variability in the dynamics of the stream of thought.

Correction: Intrinsic motivation for choice varies with individual risk attitudes and the controllability of the environment.

[This corrects the article DOI: 10.1371/journal.pcbi.1010551.].

Intrinsic motivation for choice varies with individual risk attitudes and the controllability of the environment.

When deciding between options that do or do not lead to future choices, humans often choose to choose. We studied choice seeking by asking subjects to first decide between a choice opportunity or performing a computer-selected action, after which they either chose freely or performed the forced action. Subjects preferred choice when these options were equally rewarded, even deterministically, and traded extrinsic rewards for opportunities to choose. We explained individual variability in choice seeking using reinforcement learning models incorporating risk sensitivity and overvaluation of rewards obtained through choice. Model fits revealed that 28% of subjects were sensitive to the worst possible outcome associated with free choice, and this pessimism reduced their choice preference with increasing risk. Moreover, outcome overvaluation was necessary to explain patterns of individual choice preference across levels of risk. We also manipulated the degree to which subjects controlled stimulus outcomes. We found that degrading coherence between their actions and stimulus outcomes diminished choice preference following forced actions, although willingness to repeat selection of choice opportunities remained high. When subjects chose freely during these repeats, they were sensitive to rewards when actions were controllable but ignored outcomes-even positive ones-associated with reduced controllability. Our results show that preference for choice can be modulated by extrinsic reward properties including reward probability and risk as well as by controllability of the environment.