Thus, increasing activation across conditions must be explained in terms of the increasing diversity and causal/intentional complexity of actions rather than

their simple quantity. There are four action types that are substantially more numerous in, or unique to, Acheulean stimuli: hammerstone grip shifts; hammerstone changes; core inversions; and abrasion/micro-flaking. These GSI-IX clinical trial actions are all components of the distinctive ‘platform preparation’ operation discussed above, and their frequency directly reflects the greater technological complexity of Late Acheulean toolmaking. This complexity includes increased contingency on detailed variation in hammerstone properties, grips and gestures, and in core morphology, orientation and support, as well as a greater hierarchical depth of action planning. Subjects lay supine in the 3T Siemens Allegra MRI scanner at the Wellcome Trust Centre for Neuroimaging, pads positioned on the side of the head to reduce movement. Subjects underwent six sessions of approximately 7 min, and each session comprised 12 trials, corresponding to one repetition of six experimental conditions defined by a three × two factorial plan. 1. Stimulus: 20-s video clips of the Control stimulus, Oldowan or Acheulean toolmaking. 2. Task: following stimulus presentation, subjects were instructed either to simulate

themselves PF-02341066 datasheet continuing to perform the action they saw (Imagine) or to decide whether, in their opinion, the actor was successful in achieving his goal (Evaluate). Prior to entering the scanner, subjects were instructed to watch each video ‘carefully’, to ‘try to understand what the demonstrator is doing’ and that

after each video they would be ‘asked to do one of two things’, which were then SDHB explained. In the scanner, each trial was started by the presentation of the stimulus, followed by: (i) 1.5 s of a fixation cross; (ii) a written instruction indicating the Task (‘Imagine’ or ‘Evaluate’) that remained on screen for 5 s; and (iii) a response screen displaying the appropriate question (‘Did you finish?’ or ‘Was he successful?’). The side for yes and no responses was randomly assigned to the left and right button press and indicated by the position of the words ‘Yes’ and ‘No’ on screen. The response screen remained visible for 1.5 s or until subjects replied, and was followed by a fixation screen (minimum 1 s) for a total trial duration of 29 s. In addition, each session included four 12-s rest trials, each of which started with a 1-s ‘Rest’ indication, and ended with a 1-s ‘End of rest’ indication plus a 1-s fixation screen, giving a total duration of 15 s. Trials were interleaved so that in each session, experimental trials took place in blocks of two or three.