Recollection versus Imagination: Exploring Human Memory and Cognition via Neural Language Models

Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics, pages 1970–1978 July 5 - 10, 2020. c⃝2020 Association for Computational Linguistics 1970 Recollection versus Imagination: Exploring Human Memory and Cognition via Neural Language Models Maarten Sap‡†∗ Eric Horvitz† Yejin Choi‡♦ Noah A. Smith‡♦ James W. Pennebaker♣ †Microsoft Research ‡Paul G. Allen School for Computer Science & Engineering, University of Washington ♦Allen Institute for Artificial Intelligence ♣Department of Psychology, University of Texas at Austin msap@cs.washington.edu, horvitz@microsoft.com Abstract We investigate the use of NLP as a measure of the cognitive processes involved in story- telling, contrasting imagination and recollec- tion of events. To facilitate this, we collect and release HIPPOCORPUS, a dataset of 7,000 sto- ries about imagined and recalled events. We introduce a measure of narrative flow and use this to examine the narratives for imagined and recalled events. Additionally, we measure the differential recruitment of knowledge at- tributed to semantic memory versus episodic memory (Tulving, 1972) for imagined and re- called storytelling by comparing the frequency of descriptions of general commonsense events with more specific realis events. Our analyses show that imagined stories have a substantially more linear narrative flow, com- pared to recalled stories in which adjacent sen- tences are more disconnected. In addition, while recalled stories rely more on autobio- graphical events based on episodic memory, imagined stories express more commonsense knowledge based on semantic memory. Fi- nally, our measures reveal the effect of narra- tivization of memories in stories (e.g., stories about frequently recalled memories flow more linearly; Bartlett, 1932). Our findings high- light the potential of using NLP tools to study the traces of human cognition in language. 1 Introduction When telling stories, people draw from their own experiences (episodic knowledge; Conway et al., 1996, 2003) and from their general world knowl- edge (semantic knowledge; Bartlett, 1932; Oatley, 1999). For example, in Figure 1 (top), a recalled story about a birth will likely recount concrete events from that day, relying heavily on the au- thor’s episodic memory (Tulving, 1972). On the ∗ Research conducted during an internship at Microsoft Research. ….her husband called me and then drove her to the hospital. I joined her at the hospital. When we got the hospital things got complicated. Her husband tried his best to be with her and to keep her strong. She eventually delivered perfectly. My daughter gave birth to her first child. She and her husband were overwhelmed by emotions. RECALLED We recently attended a family wedding. It was the first time in a decade we all got together. …My older brother is getting married to a rich tycoon lady. He will be very happy. I hope he doesn’t get too greedy. IMAGINED PersonX gets married PersonX to be happy causes # concrete events: 7 # concrete events: 1 Figure 1: Snippets from two stories from HIPPOCOR- PUS (top: recalled, bottom: imagined). Concrete or realis events (in gray) are more frequent in re- called stories, whereas general or commonsense events (underlined) are associated with …

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