Planning for a future, rather than a current, mental state is a cognitive process generally viewed as uniquely human. Here, however, I shall report on a decade of observations of spontaneous planning by a male chimpanzee in a zoo. The planning actions, which took place in a calm state, included stone caching and the manufacture of discs from concrete, objects later used as missiles against zoo visitors during agitated chimpanzee dominance displays. Such planning implies advanced consciousness and cognition traditionally not associated with nonhuman animals [1]. Spontaneous and unambiguous planning behaviours for future states by non-humans have not previously been reported, and anecdotal reports, describing single occasions, are exceptionally scarce[2], [3] and [4]. This dearth of observations is arguably the main reason for not ascribing cognitive foresight to nonhuman animals [1]. To date, the surprisingly few controlled demonstrations of planning for future states by animals are experimentallyinduced behaviours in great apes [5], [6] and [7] and corvids [8] and [9]. The observational findings in this report suggest that these laboratory results are not experimental artefacts, at least in the case of great apes.
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