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Helpers’ first tool selection and offer to their conspecific partner. Each condition [(A) first “can see”, (B) “cannot see”, and (C) second “can see” condition] presented participants in the recipient booth with one of two tool-use situations (“stick” or “straw”). Graphs are based on the data from three participants (Ai, Cleo, and Pal) who completed all of the conditions based on an A–B–A design. For the statistical analysis, see Table 1.
