Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Psychology

Supervisor

Owen, Adrian M.

Abstract

The present study sought to determine the extent of conscious awareness and implicit memory formation of a narrative presented during sleep. Participants were played an excerpt of J.D. Salinger’s Pretty Mouth and Green My Eyes while napping. Afterwards, participants completed a task designed to assess implicit memory to determine if they had formed any memories about words that were either directly stated in the story, or directly related to the plot. Participants who heard the story while asleep responded more quickly to words that had appeared in the story than to words from another story they had not heard. Exactly the same pattern of results was observed in a second group of participants who heard the same story while fully awake. These findings suggest that sleepers are capable of higher-level processing of complex naturalistic stimuli and can form implicit memories of this information like wakeful participants, despite lacking explicit awareness.

Summary for Lay Audience

Although sleepers show low levels of arousal, this does not mean that they are completely unaware of their surroundings. Some awareness during sleep is vital in case something important or dangerous happens in our surroundings. However, we don’t know how much information can be processed by the sleeping brain.

Awareness is often accompanied by memory formation (of the information being experienced). We often think of this as explicit memory; that is the conscious laying down and subsequent recall of information. However, much of what is remembered during normal awareness results from implicit memory. To test for implicit memories, we usually look for a facilitation of performance on tasks that contain the remembered information, rather than explicit recall. Evidence exists to suggest that sleep helps to consolidate implicit memories, resulting in better subsequent task performance, even if the person isn’t aware of this improvement. What is less clear, is whether implicit memories can be formed while a person is sleeping, rather than just strengthened.

We investigated implicit memory formation of an engaging narrative (J.D. Salinger’s Pretty Mouth and Green My Eyes) while people were sleeping. An Experimental group were played Pretty Mouth and Green My Eyes while sleeping. A Story Control group were played Pretty Mouth and Green My Eyes while awake. A No-Story control group did not hear Pretty Mouth and Green My Eyes at all. Afterwards, all groups completed a test of implicit memory for words that were either directly stated in Pretty Mouth and Green My Eyes or related to words or concepts that occurred in the narrative. The Experimental and Story Control groups responded significantly faster to these words than control words that neither appeared directly nor were related to the narrative. The No-Story control group did not show this effect, confirming that the improvement observed in the other two groups was the result of implicit memory. These results show that people are capable for forming new implicit memories of complex narrative information while sleeping, in the absence of explicit awareness.

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