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Episodic-like memory during cache recovery by scrub jays


The recollection of past experiences allows us to recall what a particular event was, and where and when it occurred1,2, a form of memory that is thought to be unique to humans3. It is known, however, that food-storing birds remember the spatial location4,5,6 and contents6,7,8,9 of their caches. Furthermore, food-storing animals adapt their caching and recovery strategies to the perishability of food stores10,11,12,13, which suggests that they are sensitive to temporal factors. Here we show that scrub jays (Aphelocoma coerulescens) remember ‘when’ food items are stored by allowing them to recover perishable ‘wax worms’ (wax-moth larvae) and non-perishable peanuts which they had previously cached in visuospatially distinct sites. Jays searched preferentially for fresh wax worms, their favoured food, when allowed to recover them shortly after caching. However, they rapidly learned to avoid searching for worms after a longer interval during which the worms had decayed. The recovery preference of jays demonstrates memory of where and when particular food items were cached, thereby fulfilling the behavioural criteria for episodic-like memory in non-human animals.

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Figure 1: Conditions and contents of the caching tray on different phases of 4-h and 124-h training and trials.
Figure 2: Mean number of inspections directed to the peanut and worm sides of the storage trays (error bars represent mean standard error for these contrasts) during the recovery phase of 4-h and 124-h test trials.

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This work was supported by grants from the NIH and the Whitehall Foundation toN.S.C. and from the BBSRC to A.D. We thank A. Quaglino, M. Caun, J. Greig, D. Griffiths, K. Sanford, E. Krebs and G. Krebs for their help with aspects of the experiment; E. Tulving for discussion and inspiration; and K. Britten, R. Gerlai, J. Krebs, D. Lee, P. Marler, L. Miyasato, R. Morris, K. Sanford, E.Tulving and A. Quaglino for comments on the manuscript.

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Correspondence to Nicola S. Clayton.

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Clayton, N., Dickinson, A. Episodic-like memory during cache recovery by scrub jays. Nature 395, 272–274 (1998).

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