Reply to Martens: Various factors may enable large populations to enhance cumulative cultural evolution, but more evidence is needed

Martens (1) suggests that including model-based bias (e.g., prestige) in our experiment would have enhanced cumulative cultural evolution (CCE) in the larger populations reported in our paper (2). This is a plausible hypothesis, but not one our experiment was designed to test. Given the controversy around the relationship between population size and CCE (3), our experiment was designed to isolate the basic effect of population size on CCE by excluding extraneous factors, including model-based bias. In our experiment increasing population size did not enhance CCE. We do not conclude that larger populations do not enhance CCE but that other factors may be necessary to see this benefit.Output Type: Lette

Increasing population size can inhibit cumulative cultural evolution

The extent to which larger populations enhance cumulative cultural evolution (CCE) is contentious. We report a large-scale experiment (n = 543) that investigates the CCE of technology (paper planes and their flight distances) using a transmission-chain design. Population size was manipulated such that participants could learn from the paper planes constructed by one, two, or four models from the prior generation. These social-learning conditions were compared with an asocial individual-learning condition in which individual participants made repeated attempts at constructing a paper plane, without having access to any planes produced by other participants. Larger populations generated greater variation in plane performance and gave participants access to better-adapted planes, but this did not enhance CCE. In fact, there was an inverse relationship between population size and CCE: plane flight distance did not improve over the experimental generations in the 2-Model and 4-Model conditions, but did improve over generations in the 1-Model social-learning condition. The incremental improvement in plane flight distance in the 1-Model social-learning condition was comparable to that in the Individual Learning condition, highlighting the importance of trial-and-error learning to artifact innovation and adaptation. An exploratory analysis indicated that the greater variation participants had access to in the larger populations may have overwhelmed their working memory and weakened their ability to selectively copy the best-adapted plane(s). We conclude that larger populations do not enhance artifact performance via CCE, and that it may be only under certain specific conditions that larger population sizes enhance CCE

Increasing Population Size Can Inhibit Cumulative Cultural Evolution

The extent to which larger populations enhance cumulative cultural evolution (CCE) is contentious. We report a large-scale experiment (N=543) that investigates the CCE of technology (paper planes and their flight distances) using a transmission chain design. Population size was manipulated such that participants could learn from the paper planes constructed by 1, 2 or 4 models from the prior generation. These social learning conditions were compared to an asocial Individual Learning condition in which individual participants made repeated attempts at constructing a paper plane, without having access to any planes produced by other participants. Larger populations generated greater variation in plane performance and gave participants access to better-adapted planes, but this did not enhance CCE. In fact, there was an inverse relationship between population size and CCE: plane flight distance did not improve over the experimental generations in the 2-Model and 4-Model conditions, but did improve over generations in the 1-Model social learning condition. The incremental improvement in plane flight distance in the 1-Model social learning condition was comparable to that in the Individual Learning condition, highlighting the importance of trial-and-error learning to artefact innovation and adaptation. In the context of this experiment, we conclude that larger populations do not enhance artefact performance via CCE, and that it may be only under certain specific conditions that larger population sizes enhance CCE

Population Size and Cumulative Cultural Evolution: Fewer Heads Can Be Better than Many

The extent to which larger populations enhance cumulative cultural evolution (CCE) is contentious. We report a large-scale experiment (N=543) that investigates the CCE of technology (paper planes and their flight distances) using a transmission chain design. Population size was manipulated such that participants could learn from the paper planes constructed by 1, 2 or 4 models from the prior generation. These social learning conditions were compared to an asocial Individual Learning condition in which individual participants made repeated attempts at constructing a paper plane, without having access to any planes produced by other participants. Larger populations generated greater variation in plane performance and gave participants access to better-adapted planes, but this did not enhance CCE. In fact, there was an inverse relationship between population size and CCE: plane flight distance did not improve over the experimental generations in the 2-Model and 4-Model conditions, but did improve over generations in the 1-Model social learning condition. The incremental improvement in plane flight distance in the 1-Model social learning condition was comparable to that in the Individual Learning condition, highlighting the importance of trial-and-error learning to artefact innovation and adaptation. In the context of this experiment, we conclude that larger populations do not enhance artefact performance via CCE, and that it may be only under certain specific conditions that larger population sizes enhance CCE

Gesture is the Primary Modality for Language Creation

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 (997 distinct words) using either gesture or non-linguistic vocalisation. Experiment 1 is a cross-cultural study, with signal Producers sampled from Australia (N=30, Mage=32.63, SD=12.42) and Vanuatu (N=30, Mage=32.40, SD=11.76). Experiment 2 is a cross-experiential study in which Producers were either sighted (N=10, Mage=39.60, SD=11.18) or severely vision-impaired (N=10, Mage=39.40, SD=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

Gesture is the primary modality for language creation

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, Mage = 32.63, s.d. = 12.42) and Vanuatu (n = 30, Mage = 32.40, s.d. = 11.76). Experiment 2 is a cross-experiential study in which Producers were either sighted (n = 10, Mage = 39.60, s.d. = 11.18) or severely vision-impaired (n = 10, Mage = 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