Developmental studies show that it takes longer for children learning spoken languages to acquire viewpoint- dependent spatial relations (e.g., "left-right", "front- behind"), compared to the ones that do not (e.g., "in", "on", "under"). The current study investigates how children learn to express viewpoint-dependent relations in a sign language where depicted spatial relations can be communicated in an analogue manner in the space in front of the body or by using body-anchored signs (e.g., tapping the right and left hand/arm to mean LEFT and RIGHT). Our results indicate that visual-spatial modality might have a facilitating effect on learning to express these spatial relations (especially in encoding of "left- right") in a sign language (i.e., Turkish Sign Language) compared to a spoken language (i.e., Turkish).
Sümer et al. (Wed,) studied this question.