RESUMO
The association between threat perception and motor execution, mediated by evolved precaution systems, often results in ritual-like behavior, including many idiosyncratic acts that seem irrelevant to the task at hand. This study tested the hypothesis that threat-detection during performance of a risky motor task would result in idiosyncratic activity that is not necessary for task completion. We asked biology students to follow a particular set of instructions in mixing three solutions labeled "bio-hazardous" and then repeat this operation with "non-hazardous" substances (or vice versa). We observed a longer duration of the overall performance, a greater repertoire of acts, longer maximal act duration, and longer mean duration of acts in the "risky" task when it was performed before the "non-risky" task. Some, but not all, of these differences were eliminated when a "non-risky" task preceded the "risky" one. The increased performance of idiosyncratic unnecessary activity is in accordance with the working hypothesis of the present study: ritualized idiosyncratic activities are performed in response to a real or illusionary threat, as a means to alleviate anxiety.
RESUMO
Our daily activities are comprised of motor routines, which are behavioral templates with specific goals, typically performed in an automatic fixed manner and without much conscious attention. Such routines can seem to resemble pathologic rituals that dominate the motor behavior of obsessive-compulsive disorder (OCD) and autistic patients. This resemblance raises the question of what differentiates and what is common in normal and pathologic motor behavior. Indeed, pathologic motor performance is often construed as an extended stereotyped version of normal everyday routines. In this study we applied ethological tools to analyze six motor routines performed by 60 adult human volunteers. We found that longer normal everyday routines included more repetitions, but not more types of acts, and that in each routine, most acts were performed either by all individuals (pragmatic acts) or by only one individual (idiosyncratic components). Thus, normal routines consist in a relatively rigid part that is shared by all individuals that perform the routine, and a flexible part that varies among individuals. The present results, however, do not answer the question of whether the flexible individual part changes or remains constant over routine repetition by the same person. Comparing normal routines with OCD rituals revealed that the latter comprise an exaggeration of the idiosyncratic component. Altogether, the present study supports the view that everyday normal routines and pathologic rituals are opposite processes, although they both comprise rigid motor behavioral sequences.
