When True Inferences Produce False Memories

Flexible Retrieval: When True Inferences Produce False Memories

Alexis C. Carpenter and Daniel L. Schacter Harvard University

Episodic memory involves flexible retrieval processes that allow us to link together distinct episodes, make novel inferences across overlapping events, and recombine elements of past experiences when imagining future events. However, the same flexible retrieval and recombination processes that underpin these adaptive functions may also leave memory prone to error or distortion, such as source misattri- butions in which details of one event are mistakenly attributed to another related event. To determine whether the same recombination-related retrieval mechanism supports both successful inference and source memory errors, we developed a modified version of an associative inference paradigm in which participants encoded everyday scenes comprised of people, objects, and other contextual details. These scenes contained overlapping elements (AB, BC) that could later be linked to support novel inferential retrieval regarding elements that had not appeared together previously (AC). Our critical experimental manipulation concerned whether contextual details were probed before or after the associative inference test, thereby allowing us to assess whether (a) false memories increased for successful versus unsuc- cessful inferences, and (b) any such effects were specific to after compared with before participants received the inference test. In each of 4 experiments that used variants of this paradigm, participants were more susceptible to false memories for contextual details after successful than unsuccessful inferential retrieval, but only when contextual details were probed after the associative inference test. These results suggest that the retrieval-mediated recombination mechanism that underlies associative inference also contributes to source misattributions that result from combining elements of distinct episodes.

Keywords: inference, false memory, episodic memory, memory, associative processes

Supplemental materials: http://dx.doi.org/10.1037/xlm0000340.supp

Episodic memory allows individuals to recollect particular past experiences (Tulving, 2002). It has been well established that episodic memories are not literal representations of past experi- ences, but instead depend on constructive processes that are some- times prone to error and distortion (cf., Bartlett, 1932; Brainerd & Reyna, 2005; Loftus, Miller, & Burns, 1978; McClelland, 1995; Roediger, 1996; Schacter, 1996). Such memory errors can arise as a consequence of multiple processes, including knowledge- or schema-based inferences made about the meaning of observed actions or events, which are later integrated into memories of presented materials, such as sentences and stories (e.g., Alba & Hasher, 1983; Bransford, Barclay, & Franks, 1972; Bransford & Franks, 1971); activation of associations to semantically related words that may produce subsequent false recognition of a nonpre- sented word that is strongly associated to the list items that were presented (e.g., Gallo, 2006; Roediger & McDermott, 1995); and

a variety of influences that operate during retrieval of past expe- riences, such as misleading suggestions or instructions to imagine what might have happened earlier (Loftus, 2003, 2005; Shaw & Porter, 2015).

While these and other forms of memory distortion could be viewed as flaws or defects in episodic memory, a number of researchers have built on Bartlett’s (1932) seminal insights and suggest instead that such errors can be viewed as byproducts of adaptive constructive processes (Schacter, 2012) that play a func- tional role in memory but produce errors or distortions as a direct consequence of doing so (cf., Howe, 2011; Howe, Wilkinson, Garner, & Ball, 2016; Newman & Lindsay, 2009; Schacter, 2001; Schacter, Guerin, & St. Jacques, 2011). Bartlett (1932), of course, focused on the functional role of schemata in guiding constructive retrieval, which he maintained “must always be supposed to be operating in any well-adapted organic response” (p. 201) but also contributed to the memory distortions that he documented. Others have argued that such well-established memory errors as the misinformation effect and associative false recognition may re- flect, respectively, the operation of adaptive memory updating processes and retention of themes and meanings (for review, see Schacter et al., 2011). More recently, it has become increasingly clear that episodic memory supports a variety of cognitive func- tions, including imagining future experiences (e.g., Schacter et al., 2012; Szpunar, 2010), inferential processing (e.g., Zeithamova, Dominick, & Preston, 2012; Zeithamova & Preston, 2010), means- end problem solving (e.g., Madore & Schacter, 2014; Sheldon, McAndrews, & Moscovitch, 2011), and divergent creative think-

This article was published Online First December 5, 2016. Alexis C. Carpenter and Daniel L. Schacter, Department of Psychology

and Center for Brain Science, Harvard University. This research was supported by National Institute of Mental Health

Grant MH060941 and National Institute on Aging Grant AG08441 to D.L.S. We thank Karen Campbell, Aleea Devitt, Alison Preston, and Preston Thakral for helpful comments on a draft of the manuscript.

Correspondence concerning this article should be addressed to Alexis C. Carpenter, Department of Psychology, Harvard University, 33 Kirkland Street, Cambridge, MA 02138. E-mail: alexiscarpenter@g.harvard.edu

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