Background: When performing the clock-drawing test healthy participants often draw the clock face using a counter clockwise movement. The reason for this circular directional bias is not known. These actions may be related to the development of motor or attentional programs that associate leftward with downward movements, and rightward with upward movements.
Methods: To further examine this down-left, up-right programming hypothesis, we examined the direction of circular movements made during cursive writing by dividing the first curved movements into the following pairs, up versus down, and leftward versus rightward.
Results and conclusions: With almost all the letters analyzed, when initially moving upward there was a simultaneous rightward movement and when initially moving downward a leftward movement. The results suggest that there appears to be a relationship between downward and leftward movements as well as between upward and right rightward movements. In addition, there is some evidence to suggest that the right-upward movements may be mediated by the left hemisphere and left-downward movements by the right hemisphere. Although our results suggest motor or spatial attentional programs may account for counter clockwise face drawing, activities such as learned writing direction may influence this spatial bias. Therefore, additional research is needed to better understand if these spatial biases are learned or intrinsic and the neuropsychological mechanisms that might account for these asymmetries.
Keywords: Action bias; Directional attentional bias; Drawing clock face; Drawing direction.
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