Preschool children's proto-episodic memory assessed by deferred imitation

Abstract

In two experiments, both employing deferred imitation, we studied the developmental origins of episodic memory in two- to three-year-old children by adopting a “minimalist” view of episodic memory based on its What–When–Where (“WWW”: spatiotemporal plus semantic) content. We argued that the temporal element within spatiotemporal should be the order/simultaneity of the event elements, but that it is not clear whether the spatial content should be egocentric or allocentric. We also argued that episodic recollection should be configural (tending towards all-or-nothing recall of the WWW elements). Our first deferred imitation experiment, using a two-dimensional (2D) display, produced superior-to-chance performance after 2.5 years but no evidence of configural memory. Moreover, performance did not differ from that on a What–What–What control task. Our second deferred imitation study required the children to reproduce actions on an object in a room, thereby affording layout-based spatial cues. In this case, not only was there superior-to-chance performance after 2.5 years but memory was also configural at both ages. We discuss the importance of allocentric spatial cues in episodic recall in early proto-episodic memory and reflect on the possible role of hippocampal development in this process.

Keywords:

• Episodic memory
• Hippocampus
• Deferred imitation

We are grateful to The Leverhulme Trust (UK) for funding this research by a grant to the second and third authors. We are also grateful to Dr Mike Aitken for advice about statistical modelling, to Sanja Abbott for iPad programming and to the parents of the children for giving up their time.

We are grateful to The Leverhulme Trust (UK) for funding this research by a grant to the second and third authors. We are also grateful to Dr Mike Aitken for advice about statistical modelling, to Sanja Abbott for iPad programming and to the parents of the children for giving up their time.

Notes

¹ The thought experiment: You have a re-experiential memory for event E and know it was a unique autobiographical event, but cannot recall whether E took place last week or a month ago. What warrant is there for denying that it is an episodic memory? The length of time between E and the present would appear to be a semantic matter.

² This term is not ideal given that our procedure might be regarded as “observational causal learning” (as in Meltzoff, Waismeyer, & Gopnick, 2012). However, as the term “deferred imitation” is used in the memory, rather than the causal, literature, we have used that. Note too that because the children are not given the opportunity to act on the materials before the retention interval, as in Bauer's (2013) procedure of “elicited” imitation, we do not use the term elicited imitation.

³ In the What-When-Where task, there was ½ chance of picking the correct icon animal initially, then a ¼ chance of moving it to the correct corner, then another ½ chance of picking the second animal correctly, followed by a ¼ chance of moving it to the correct corner. In the What-What-What task there was a ½ chance of picking one of the two correct hats, followed by a ½ chance of putting this on the correct animal, followed by a ½ chance of putting this in the correct box; after this a ¼ chance of picking the other correct hat. As there was now only one animal remaining this was followed by a ½ chance of putting the hat-wearing animal in the correct box.

⁴ Touching a handle without moving it was not coded as an action.

⁵ Fisher's Exact Test was used rather than Chi as two of the four cells in the contingency table had an expected value of less than 5.

⁶ Four locations acted on twice times 2 orders = 32.

⁷ This is not to deny that the semantic binding is can also take place in the hippocampus (Manns, Hopkins, & Squire, 2003), a fact relevant to our What–What–What control task.