Slip of the tongue: Implications for evolution and language development

Abstract

a b s t r a c tA prevailing theory regarding the evolution of language implicates a gestural stage prior to the emergence of speech. In support of a transition of human language from a gestural to a vocal system, articulation of the hands and the tongue are underpinned by overlapping left hemisphere dominant neural regions. Behavioral studies demonstrate that human adults perform sympathetic mouth actions in imitative synchrony with manual actions. Additionally, right-handedness for precision manual actions in children has been correlated with the typical development of language, while a lack of hand bias has been associated with psychopathology. It therefore stands to reason that sympathetic mouth actions during fine precision motor action of the hands may be lateralized. We employed a fine-grained behavioral coding paradigm to provide the first investigation of tongue protrusions in typically developing 4-year old children. Tongue protrusions were investigated across a range of cognitive tasks that required varying degrees of manual action: precision motor action, gross motor action and no motor actions. The rate of tongue protrusions was influenced by the motor requirements of the task and tongue protrusions were significantly right-biased for only precision manual motor action (p < .001). From an evolutionary perspective, tongue protrusions can drive new investigations regarding how an early human communication system transitioned from hand to mouth. From a developmental perspective, the present study may serve to reveal patterns of tongue protrusions during the motor development of typically developing children.

Congruency Effect Between Articulation and Grasping in Native English Speakers

“…Hence, this finding is in accordance with suggestions that speech-hand connections are evolutionally old, and not some learned abstract associations, and that their motor networks are partially overlapping [5,6,8,13]. In the field of language acquisition, recent results demonstrate that manual actions can drive tongue protrusions of small children [14]. Comparing these results to our results, which indicated a strong connection between specific grasp actions and articulation, lead us to hypothesize that manual actions could be used to assist speech development in children.…”

“…Precision grip (631 ms) was performed more quickly than power grip (673 ms). Importantly, the syllable-grip interaction was also significant, F (1,14) …”

“…For the manual reaction times there was a main effect for grip, F (1,14)=15.262, p=.002, η 2 =0.522. Precision grip (631 ms) was performed more quickly than power grip (673 ms).…”

Systematic Influence of Perceived Grasp Shape on Speech Production

“…In line with these mouth-hand mimicry theories, Darwin already in 1872 noted that people seem to have this kind of tendency as they, for example, often involuntarily clench and unclench their jaws when they are cutting something with scissors [17]. More recently, a similar phenomenon has been observed in young children who perform sympathetic mouth actions, such as tongue protrusions, in imitative synchrony with manual actions [18]. …”

Connections of Grasping and Horizontal Hand Movements with Articulation in Czech Speakers

“…It has been observed that young children (Forrester and Rodriguez, 2015) and chimpanzees (Waters and Fouts, 2002) tend to perform mouth movements, such as tongue protrusions, in imitative synchrony with fine-motor hand actions. Taking this view a step further, Ramachandran and Hubbard (2001) suggested that some articulations can even be thought of as mimes of hand actions.…”