Delays without mistakes: response time and error distributions in dual-task.
BACKGROUND
When two tasks are presented within a short interval, a delay in the execution of the second task has been systematically observed. Psychological theorizing has argued that while sensory and motor operations can proceed in parallel, the coordination between these modules establishes a processing bottleneck. This model predicts that the timing but not the characteristics (duration, precision, variability...) of each processing stage are affected by interference. Thus, a critical test to this hypothesis is to explore whether the quality of the decision is unaffected by a concurrent task.


RESULTS
In number comparison--as in most decision comparison tasks with a scalar measure of the evidence--the extent to which two stimuli can be discriminated is determined by their ratio, referred as the Weber fraction. We investigated performance in a rapid succession of two non-symbolic comparison tasks (number comparison and tone discrimination) in which error rates in both tasks could be manipulated parametrically from chance to almost perfect. We observed that dual-task interference has a massive effect on RT but does not affect the error rates, or the distribution of errors as a function of the evidence.


CONCLUSIONS
Our results imply that while the decision process itself is delayed during multiple task execution, its workings are unaffected by task interference, providing strong evidence in favor of a sequential model of task execution.
Kamienkowski
Juan Esteban
JE
Integrative Neuroscience Laboratory, Physics Department, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina. juank@df.uba.ar
Sigman
Mariano
M
D000161:Acoustic Stimulation; D000328:Adult; D001931:Brain Mapping; D003071:Cognition; D006801:Humans; D007858:Learning; D008297:Male; D008606:Mental Processes; D015233:Models, Statistical; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D012033:Refractory Period, Psychological; D015203:Reproducibility of Results; D013997:Time Factors; D014796:Visual Perception
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