Factors influencing manual discrimination of orientations in 5-month-old infants.

Factors affecting manual discrimination of spatial orientations and orientation preferences in 5-month-old infants have been investigated by using a familiarisation/reaction to novelty procedure. In the first experiment we explored whether the 'vertical preference' observed by Gentaz and Streri (2004 Journal of Cognitive Neuroscience 16 1-7) and Kerzerho et al (2005 Neuro Report 16 1833-1837) is an intrinsic preference or whether it is due to familiarisation. In the second experiment we examined whether the magnitude of angular deviation to the vertical influences the direction of preference. Results showed that when both gravitational vertical and body axes were aligned, the intrinsic 'vertical preference' exists when the angular difference between the two orientations was 10 degrees. When the angular deviation from the vertical was greater than 10 degrees, the novel orientation was preferred. This modification of orientation preference in the manual discrimination of orientation by 5-month-old infants is discussed in relation to the magnitude of the angular deviation to the gravitational vertical and the spatial reference cues available in each condition.