Mid-level ‘intentions in action’ represented in the anterior inferior parietal and the ventral prefrontal cortices, though likely to
be inaccurate at first, appear to be important across skill levels and may play an important role in guiding such practice, perhaps contributing to the high fidelity of human social learning (the ‘ratchet effect’: Tomasello, 1999; Tennie et al., 2009). The effect of Toolmaking complexity in the anterior inferior parietal lobule in particular suggests that this phylogenetically derived (Peeters et al., 2009) region may have played a key role in human technological evolution 2.6–0.5 million years ago. This research was funded by European Union project HANDTOMOUTH. We thank Bruce Bradley for Lenvatinib molecular weight acting as the expert demonstrator, DAPT cell line and Stefan Vogt and an anonymous reviewer for helpful comments. Abbreviations BA Brodmann area fMRI functional magnetic resonance imaging PET positron emission tomography Fig. S1. Handaxes produced (a–c) by Trained subjects, (d) by the expert demonstrator, and (e) from the Middle Pleistocene (ca. 500 000 years
ago) site of Boxgrove, West Sussex, UK. Fig. S2. Local brain activity in Oldowan–Control (left) and Acheulean–Control (right) irrespective of subject expertise (FDR P < 0.05, extent k > 20). To more directly compare current results with previous FDG-PET studies of Oldowan and Acheulean tool-making execution, we examined separate contrasts of Oldowan and Acheulean tool-making with the Control. This yielded activations of left ventral premotor cortex in both contrasts (Oldowan: −56, 8, 22; Acheulean: −58, 10, 32), and of right pars triangularis in the Acheulean (46, 36, 4) but not Oldowan contrast. This directly matches results from Ribonucleotide reductase the execution of Oldowan
(ventral premotor cortex: −52, 6, 28) and Acheulean (ventral premotor cortex: −52, 6, 28; pars triangularis: 48, 34, 10) tool-making (Stout et al., 2008; Table 2). Fig. S3. Local brain activity in Oldowan–Control for Naïve (left), Trained (centre) and Expert (right) subjects (FDR P < 0.05, extent k > 20). Fig. S4. Local brain activity in Acheulean–Control for Naïve (left), Trained (centre) and Experts (right) subjects (FDR P < 0.05, extent k > 20). Table S1. Brain activity in response of the observation of Oldowan compared with Control stimuli, common to the three groups (minimum statistic conjunction) and by subject expertise (exclusive masking). All results are FDR P < 0.05, extent k > 20. Table S2. Brain activity in response of the observation of Acheulean compared with Control stimuli, common to the three groups (minimum statistic conjunction) and by subject expertise (exclusive masking). All results are FDR P < 0.05, extent k > 20. Video S1. Examples of Control, Oldowan and Acheulean stimuli used in the experiment. As a service to our authors and readers, this journal provides supporting information supplied by the authors.