Gesture is the primary modality for language creation

Abstract

How language began is one of the oldest questions in science, but theories remain speculative due to a lack of direct evidence. Here, we report two experiments that generate empirical evidence to inform gesture-first and vocal-first theories of language origin; in each, we tested modern humans' ability to communicate a range of meanings (995 distinct words) using either gesture or non-linguistic vocalization. Experiment 1 is a cross-cultural study, with signal Producers sampled from Australia (n = 30, M_age = 32.63, s.d. = 12.42) and Vanuatu (n = 30, M_age = 32.40, s.d. = 11.76). Experiment 2 is a cross-experiential study in which Producers were either sighted (n = 10, M_age = 39.60, s.d. = 11.18) or severely vision-impaired (n = 10, M_age = 39.40, s.d. = 10.37). A group of undergraduate student Interpreters guessed the meaning of the signals created by the Producers (n = 140). Communication success was substantially higher in the gesture modality than the vocal modality (twice as high overall; 61.17% versus 29.04% success). This was true within cultures, across cultures and even for the signals produced by severely vision-impaired participants. The success of gesture is attributed in part to its greater universality (i.e. similarity in form across different Producers). Our results support the hypothesis that gesture is the primary modality for language creation.

Keywords: gesture; icon; language evolution; language origin; universal; vocalization.

Figure 1.

Summary statistics and distributional information for all dependent variables. (a–d) Bars indicate the cell means and the data points indicate the mean score for each Producer/Interpreter, error bars are the 95% bootstrapped confidence intervals and violins provide distributional information. (a) Percentage of words Producers skipped. (b) Percentage of words successfully communicated (organized by Interpreters; the black horizontal line indicates chance communication success). (c) Interpreters' confidence they had identified the Producers’ intended word. (d) (Rated) similarity of the signals used to communicate the same words by different Producers (the black horizontal line indicates the baseline similarity). (e) shows the correlation between signal universality and communication success (the data points indicate the mean scores for each Producer). The black straight line is the linear model fit, and the grey shaded area is the bootstrapped 95% CI. Note that, for each condition, communication success was higher than chance (b) and signal similarity was higher than baseline signal similarity (d). (Online version in colour.)

Figure 2.

Summary statistics and distributional information for all dependent variables. (a–d) Bars indicate the cell means and the data points indicate the mean score for each Producer/Interpreter, error bars are the 95% bootstrapped confidence intervals and violins provide distributional information. (a) Percentage of words Producers skipped. (b) Percentage of words successfully communicated (organized by Interpreters; the black horizontal line indicates chance communication success). (c) Interpreters' confidence they had identified the Producers’ intended word. (d) (Rated) similarity of the signals used to communicate the same words by different Producers (the black horizontal line indicates the baseline similarity). (e) Correlation between signal universality and communication success (the data points indicate the mean scores for each Producer). The black straight line is the linear model fit, and the grey shaded area is the bootstrapped 95% CI. Note that for each condition, communication success was higher than chance (b) and signal similarity was higher than baseline signal similarity (d). (Online version in colour.)