title: Effects of arm weight on C-not-B task performance: implications for the motor inhibitory deficit account of search failures.
abstract: Toddlers have been found to fail on a three-location search task involving the invisible displacements of an object, namely the C-not-B task. In this task, a child is shown the experimenter's hand that contains a toy. The toy then successively disappears under the three cloths (A, B, then C). The examiner silently releases the toy under the second cloth (B). The hidden object makes a bump in the B cloth that covers it. Young children emit a strong bias toward the last cloth that the experimenter's hand passes under, and this has been labeled the C-not-B error. One possible explanation for toddlers' failures in the C-not-B task is that children lack the motor inhibitory mechanisms. To test this hypothesis, the robustness of the C-not-B error was tested, in a first experiment, against variations in body parameters. By putting additional weights on the arm, the C-not-B error was reduced substantially and the C-not-B task had a higher rate of success. Indeed, in contrast to control participants, who ignored a visual clue indicating the correct location of the hidden object and reached for the last location of the experimenter's hand, the participants with arm weights initiated their reaching movements by using the visual clue. The findings from the second control group indicate that the dramatic increase in successful performance by children with arm weights is not merely a consequence of the focus on the attention to arm movements. The motion of the experimenter's hand in space appears to have made the task difficult because toddlers had no problems inferring that a lump under a cloth indicates the existence of an object without actually having watched an object be hidden there, as demonstrated in a second experiment. The findings are consistent with the hypothesis that C-not-B task content activates a prepotent motor response that preempts full consideration of a visual clue indicating the correct location of the hidden object. We propose that the success in the C-not-B task of toddlers with additional arm weights could result from a disruption of automatic hand movement that is triggered by sensory signals, namely salient features of the C-not-B task.
authors.affiliation: Laboratoire Psychologie et Neurosciences de la Cognition, Université de Rouen, Mont-Saint-Aignan, France. james.riviere@univ-rouen.fr
authors.forename: James
authors.initials: J
authors.lastname: Rivière
authors.forename: Roger
authors.initials: R
authors.lastname: Lécuyer
mesh_terms: D001288:Attention; D001696:Biomechanical Phenomena; D002675:Child, Preschool; D003463:Cues; D004193:Discrimination Learning; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D009949:Orientation; D010364:Pattern Recognition, Visual; D018187:Personal Construct Theory; D011340:Problem Solving; D011597:Psychomotor Performance; D011930:Reaction Time; D012153:Retention, Psychology; D016474:Weight-Bearing