Grönqvist, H., Gredebäck, G., & von Hofsten, C. (2006) Developmental Asymmetries between Horizontal and Vertical Tracking. Vision Research, 46(11), 1754-176.

The development of the asymmetry between horizontal and vertical eye tracking was investigated longitudinally at 5, 7, and 9 months of age. The target moved either on a 2D circular trajectory or on a vertical or horizontal 1D sinusoidal trajectory. Saccades, smooth pur- suit, and head movements were measured. Vertical tracking was found to be inferior to horizontal tracking at all age levels. The results also show that the mechanisms responsible for horizontal and vertical tracking mutually inXuence one another in the production of 2D visual pursuit. Learning eVects were observed within-trials but no transfer between trials was found.