Symbolic artifacts present a challenge to theories of neurocognitive processing due to their dual nature: they are both physical objects and vehicles of social meanings. While their physical properties can be read of the surface structure, the meaning of symbolic artifacts depends on their embeddedness in cultural practices. In this study, participants built models of LEGO bricks to illustrate their understanding of abstract concepts. Subsequently, they were scanned with fMRI while presented to photographs of their own and others’ models. When participants attended to the meaning of the models, we observed activations associated with social cognition and semantics. In contrast, when attending to the physical properties, we observed activations related to object recognition and manipulation. Furthermore, when contrasting own and others’ models, we found activations in areas associated with autobiographical memory and agency. Our findings support a view of symbolic artifacts as neurocognitive trails of human social interactions.

Interpersonal physiological entrainment is increasingly argued to underlie rapport, empathy and even team performance. We investigate the presence, temporal development, possible mechanisms and impact of interpersonal heart rate entrainment during collective creative LEGO construction tasks. We observe a statistically significant presence and increase over time of structured entrainment, which relates to the actual unfolding and development of behavioral coordination. Heart rate entrainment does not predict rapport and perceived group competence, but behavioral coordination does. Physiological entrainment, thus, should not be considered a universal unmediated proxy for shared emotions, empathy and collective performance. Behavioral coordination – at least in tasks requiring forms of joint action – seems to be a more informative proxy for both physiological entrainment and collective experience.

When speaking to infants, adults often produce speech that differs systematically from that directed to other adults. To quantify the acoustic properties of this speech style across a wide variety of languages and cultures, we extracted results from empirical studies on the acoustic features of infant-directed speech. We analysed data from 88 unique studies (734 effect sizes) on the following five acoustic parameters that have been systematically examined in the literature: fundamental frequency (f₀), f₀ variability, vowel space area, articulation rate and vowel duration. Moderator analyses were conducted in hierarchical Bayesian robust regression models to examine how these features change with infant age and differ across languages, experimental tasks and recording environments. The moderator analyses indicated that f₀, articulation rate and vowel duration became more similar to adult-directed speech over time, whereas f₀ variability and vowel space area exhibited stability throughout development. These results point the way for future research to disentangle different accounts of the functions and learnability of infant-directed speech by conducting theory-driven comparisons among different languages and using computational models to formulate testable predictions.