The beta-binomial mixed effect model showed that imitation accuracy in the neutral condition was lower in the ASG compared to the CG at a marginally significant level (p = 0.073) while imitation accuracy in the playful condition was similar in the ASG and the CG (p = 0.891).
Results of the beta-binomial mixed effect regression model indicated that imitation frequency was significantly lower in the ASG than in the CG (ASG—CG − 23.3; 95% CI − 46.5, − 1.3; p = 0.023) and a similar trend was observed for imitation accuracy, although the difference did not reach statistical significance (ASG—CG − 17.4; 95% CI − 36.6, 1.3; p = 0.096).
Frequency and accuracy of imitation in association to mental age We tested the association between mental age (MA) and imitation performance across all trials in study 1 (playful plus neutral actions), and found a positive trend showing higher imitation frequency and accuracy in participants with higher MA across groups.