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While risk aversion can have short term benefits, this will limit long term skill acquisition and technological ceilings. We suggest that late Acheulean handaxe forms required tolerance of greater learning costs via deliberate practice, indicating 'mental time travel' and social support for learners

Simply, novices should cease knapping soon after a cutting edge is established, with further attempts at shaping tools tool increasing risk of a poor functioning tool. The novice rough-outs are similar in attrivutes to early Acheulean handaxes from Ubeidiya, which could reflect similar risk-aversion

Additionally, novice handaxes were more likely to break before completion, happening for 26% of attempts by novices and 7% for experts.

Edge crushing was recorded from handaxes and was three times higher on novice tools (1/3 of circumferences). Crushing % negatively correlates with rate of successful flakes for novices but not for experts. This indicates that knapping errors can be reversed by experts but they accumulate for novices

Recorded sequences of successful flake removals and mistrikes show clear differences between expert (top) and novice (bottom) knappers. Mistrike rate rapidly decreases for novices, outnumbered successful strikes by the end of the rough-out stage.

A PCA analysis of 3D shape and morphometric data show that expert handaxes improved much more than novices' from rough-out to final stages. Showing greater value of continued knapping for experts

We recruited 10 expert and 10 novice knappers, asking them each to replicate 4 flint handaxes, mimicking a target form. We 3D scanned handaxes as starting blanks, rough-outs (i.e. a biface prior to shaping) and finished forms. Flaking Sequences were also extrapolated from experiment footage.