Do humans use episodic memory to solve a What-Where-When memory task?

Abstract

What-Where-When (WWW) memory tasks have been used to study episodic(-like) memory in non-human animals. In this study, we investigate whether humans use episodic memory to solve such a WWW memory task. Participants are assigned to one of two treatments, in which they hide different coin types (what) in different locations (where) on two separate occasions (when). In the Active treatment, which mimics the animal situation as closely as possible, participants are instructed to memorize the WWW information; in the Passive treatment, participants are unaware of the fact that memory will be tested. In both groups, the majority of participants report using a mental time travel strategy to solve the task, and performance on a different episodic memory test significantly predicts performance on the WWW memory task. This suggests that the WWW memory task is a good test of episodic memory in humans. Participants remember locations and coins from the first hiding session better than they do those of the second hiding session, suggesting their memories may be reinforced during the second hiding session. We also investigated how well episodic memory performance predicted performance on the three aspects of the WWW memory task separately. In the Passive treatment, episodic memory performance predicts performance on all three aspects of the WWW memory task equally. However, in the Active treatment it only predicts performance on the what component. This could imply that during active encoding a different memory system is used for where and when information than during passive encoding. Encoding of what information seems to rely on episodic memory processing in both conditions.

Appendix: Episodic memory questions

All these questions were asked twice: once referring to the first hiding episode and once to the second hiding episode. Some of these were manipulated so that they were correct on day one but not day two and vice versa. Others may have been correct on both or neither day. In order to answer correctly, it is therefore important to mentally go back to the relevant episode.

• (1) Was it raining when you came to the house?

• (2) Was there a bike in the hallway?

• (3) Were there letters and fliers on the floor by the front door?

• (4) Were there coats on the coat rack in the hallway?

• (5) Was the living room door open?

• (6) Was the window in the living room open?

• (7) Was the television on when you first entered the room?

• (8) Was the kitchen door open?

• (9) Was there a rug on the floor in the centre of the room?

• (10) Were there other people in the house?

• (11) Was the light on in the living room when you first came?

• (12) Was the light on in the hallway when you first came?

• (13) Was there a poster on the wall behind the television?

• (14) Was the door on the left, before the living room open?

• (15) Was there a games console on the floor in front of the television?

• (16) Was there a guitar by the sofa near the window?