Deaf children prefer to use signs that look like the action they refer to
Children learning a spoken language need to associate arbitrary labels to the object they refer to. For example, they must learn that the word ‘pen’ refers to a thin object used for writing. However, there is nothing in the word itself giving away any of this information. The situation in deaf children learning a sign language is different because some signs referring to objects represent the shape of the object or how it is manipulated. In Turkish Sign Language (Türk İşaret Dili, TİD), for example, the sign PEN, has two possible forms. The action variant shows how a pen is manipulated while the perceptual variant depicts its thin long shape (see Figure).
Type of iconicity and sign language acquisition
"Both signs are iconic, meaning that they resemble some characteristics of the object they refer to", Gerardo Ortega, first author of the study, explains. “The type of iconicity is different, though, because one sign resembles the action performed on the object and the other one depicts the object's shape.” The researchers wanted to investigate whether different types of iconic signs would have an effect in sign language learning.
Two types of iconic signs for PEN in Turkish Sign Language (Türk İşaret Dili, TİD). The action variant (left) represents a person writing. The perceptual variant (right) represents the elongated shape of a pen.
For this study, funded by an ERC starting grant awarded to Prof. Aslı Özyürek, the researchers travelled to Istanbul, Turkey and recruited 48 deaf TID signers, 20 children and 28 adults - one of the biggest samples collected for a sign language acquisition study. Signers had to describe pictures with two objects which have an action and a perceptual sign associated with them (e.g., a pen in a cup). Children showed a clear preference for signs that mimic the action of writing when referring to a pen, but an adult would rather use the sign that resembles a pen's shape. Exceptions to this are conversations between children and their parents because they were more inclined to use the action sign.
The link between sign learning and the motor system
How can these differences be explained? The researchers argue that children have a bias for learning signs representing bodily actions because they can be easily linked to their own motoric knowledge. "It is easier for children to make associations between action signs and their referent because of their experience interacting with objects", Ortega says. “Despite the fact that caregivers know and use regularly the perceptual variant, they favour the action signs when communicating with their children because they are accommodating to their children's preference”. Unlike previous research on sign language acquisition, these findings show that vocabulary development of a spoken and sign language might follow different paths. This study also underscores the fact that learning labels for objects might be more linked to our bodily experiences than we previously thought; and that we would not easily detect this effect by looking at the development of spoken languages only.