Information Processing (at least 500 words)

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

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 , Harvard University, 33 Kirkland
Street, Cambridge, MA 02138. E-mail: [email protected]

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Journal of Experimental :
Learning, Memory, and Cognition

© 2016 American Psychological Association

2017, Vol. 43, No. 3, 335–349
0278-7393/17/$12.00 http://dx.doi.org/10.1037/xlm0000340

335

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

mailto:[email protected]

http://dx.doi.org/10.1037/xlm0000340

ing (e.g., Madore, Addis, & Schacter, 2015). An important feature
of episodic memory that supports these and other adaptive func-
tions is the capacity to flexibly retrieve and recombine information
from distinct past experiences into novel representations. For ex-
ample, according to the constructive episodic simulation hypoth-
esis (Schacter & Addis, 2007a, 2007b), the capacity to flexibly
recombine elements of past experiences is crucial for our ability to
imagine or simulate new situations that might occur in the future.
Similarly, recent evidence suggests that flexible recombination
plays a key role in our capacity to make inferences based on
distinct past events that share a common feature (Zeithamova,
Dominick, & Preston, 2012; Zeithamova & Preston, 2010).

In line with the theoretical perspectives noted earlier that em-
phasize the close link between adaptive aspects of episodic mem-
ory and susceptibility to memory errors, the constructive episodic
simulation hypothesis also holds that the functional benefits of
flexible retrieval and recombination are accompanied by a cost:
vulnerability to memory errors such as source misattribution and
false recognition that can result from mistakenly combining ele-
ments of distinct past experiences (Schacter & Addis, 2007a,
2007b; for related views, see Dudai & Carruthers, 2005; Sudden-
dorf & Corballis, 2007). There is indeed evidence that memory
errors can result from mistakenly combining features of distinct
episodic or autobiographical memories (e.g., Burt, Kemp, & Con-
way, 2004; Devitt, Monk-Fromont, Schacter, & Addis, 2016;
Odegard & Lampinen, 2004). However, we are not aware of any
study that has directly tested the central idea of the constructive
episodic simulation hypothesis that the same flexible recombina-
tion process that supports an adaptive cognitive process can also
produce memory errors that result from miscombining elements of
distinct past experiences.

To test this idea, we required a task that both requires flexible
recombination and supports an adaptive cognitive process. The
associative inference task used by Preston and colleagues fits these
requirements (e.g., Preston, Shrager, Dudukovic, & Gabrieli, 2004;
Zeithamova, Dominick, & Preston, 2012; Zeithamova & Preston,
2010). Associative inference is an adaptive process that allows
people to link together related information acquired in distinct
episodes to make novel connections that they have not directly
experienced (Zeithamova, Schlichting, & Preston, 2012). For ex-
ample, if one sees two different individuals entering the same
house on different days, retrieving and recombining details of the
two episodes allows one to infer that the two individuals are
related in some way by their relationship with the house. This kind
of flexible recombination is quite similar to the kind of flexible
recombination that is required to draw on elements of past expe-
riences to construct simulations of novel future events, as dis-
cussed by Schacter and Addis (2007a, 2007b). In previous studies
using the associative inference procedure, participants learned
direct associations between two items (AB) and then learned direct
associations between two items that included one member of the
previously studied pair (BC) and also learned indirect associations
based on the overlapping pairs (AC). Later, participants received a
memory test for both the direct AB and direct BC associations. In
addition, participants received an associative inference test for the
indirect association (AC). Here, they are told that the link between
the two items is mediated by a third item (B) that was previously
associated with both the A and C items, and to choose which of
two items was linked to A via the shared B association.

There are two ways that participants can perform successfully
on the associative inference test. First, during study of BC, par-
ticipants may bring to mind the related AB pair and encode an
integrated representation (ABC) that is later retrieved during the
associative inference test (integrative encoding; e.g., Shohamy &
Wagner, 2008). Second, participants may engage in flexible re-
combination at the time of retrieval, bringing to mind and com-
bining the previously studied AB and BC pairs during the asso-
ciative inference task. Neuroimaging evidence suggests that both
mechanisms contribute to associative inference (Zeithamova,
Dominick, & Preston, 2012; Zeithamova & Preston, 2010). In the
present study, we adapted the associative inference paradigm de-
veloped by Zeithamova and Preston (2010) to assess whether
mechanisms linked with inferential processing (i.e., retrieval-
related recombination and encoding-related integration) also con-
tribute to source memory errors. As noted earlier, pioneering
studies on memory distortion have already shown that knowledge-
or schema-driven inferences about sentences and stories can con-
tribute to memory errors (e.g., Alba & Hasher, 1983; Branford &
Franks, 1971), but the kind of inferential processing tapped by
Zeithamova and Preston’s associative inference task focuses spe-
cifically on combining elements from distinct episodes that are not
linked by preexisting knowledge or schemas, and thus likely draws
on different processes than the meaning-based inferences elicited
in classic studies of sentence and story processing. Indeed, it is
precisely because the associative inference paradigm developed by
Zeithamova and Preston (2010) targets flexible recombination
processes that link elements of distinct episodes that their para-
digm is well suited for testing the key claim of the constructive
episodic simulation hypothesis—that the same flexible retrieval
processes that are used to combine elements of distinct episodes
into functionally useful, novel representations can also produce
memory errors that result from mixing up elements of these
episodes. More generally, we attempt to determine whether the
domain of adaptive memory distortions, where a memory error
results from carrying out a cognitive operation that has demon-
strably beneficial consequences on another aspect of performance,
extends to associative inference. Although the literature on asso-
ciative inference has grown considerably during the past decade
(for review, see Schlichting & Preston, 2015), we are not aware of
any studies using the associative inference paradigm, which re-
quires combining elements of distinct episodes, that have linked
successful associative inference with memory errors.

In our version of the associative inference paradigm, during an
initial session participants study scenes that include AB items (e.g.,
a person [A] and a toy [B] in a room with a white couch; Figure
1) and then study scenes comprised of BC items (e.g., the toy [B]
and a different person [C] in a room with a brown couch). Partic-
ipants are instructed to try to learn both the direct association
between each person and object (AB and BC) and the indirect
association between the two people based on the shared object
(AC). After a delay, participants return for a second session in
which they are tested for direct associations (AB, BC) and perform
an associative inference test for novel combinations that are
linked via the B item (AC). To test whether retrieval-related
recombination processes underlying successful inference can
also contribute to memory errors, memory for contextual details
from both the AB and BC scenes is also probed (e.g., What

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336 CARPENTER AND SCHACTER

color was the couch?) followed immediately by a source mem-
ory test (In which set of images do you remember seeing this
information?). For one half of the AB and BC scenes, detail/
source memory tests were given before the test of direct (AB,
BC) and indirect (AC) associations, and for the other half, the
detail/source memory tests were given after the tests of direct
and indirect associations. For the detail/source test, a true

memory is defined as a response in which the participants both
chose the correct item and attributed the source of their memory
correctly (e.g., white couch attributed to AB scene), whereas a
false memory is defined as a response for which the participant
both chose the item from the overlapping image (e.g., BC) and
misattributed its source (e.g., brown couch attributed to AB
scene; see Methods for further details).

Session 1:
AB Encoding BC Encoding

Session 2:
Detail Source Monitoring

Associative Inference Directly Learned

What color was the couch? Where do you remember seeing this
information?

A) Brown

B) White

C) Grey

A)
set of images

B) I remember it from the
second set of images

C) I remember it from both sets
of images

D) I am unsure where I
remember this from

2121

n

1

Figure 1. Illustration of materials, stimuli, and test displays from Experiments 1a and 1b. The Session 1 section
shows one example of an AB image in which the man is item “A” and the toy truck is item “B” and the
corresponding BC image in which the boy is item “C.” The Session 2 section shows one example of a detail and
source monitoring question linked to the example AB image. For each detail question, participants saw a cutout
of the “A” or “C” individual presented to the right of the question in order to indicate to which event the question
referred. False memories occurred when participants chose both the misinformation detail (e.g., brown couch)
during the detail question and attributed the misinformation detail incorrectly to either the original event or both
events—as indicated by the red (dark grey) circles. True memories occurred when participants both chose the
correct detail during the detail question (e.g., white couch) and attributed the correct detail correctly to the
original event—as indicated by the green (light grey) circles. Other example detail questions for this ABC triad
included: Where were the stairs located? What color were the walls in the room? What was this individual
sitting/standing on? What was hanging on the wall directly behind this individual? and so forth. It is important
that all of these questions relate to two contradictory details from images AB and BC (e.g., stairs directly behind
vs. to the far left; yellow vs. white walls; wood floors vs. carpet; potted plants vs. picture frames; etc.). The green
(light grey) circles indicate the correct answer for the associative inference and directly learned questions.
Participants saw these images without the red (dark grey) and green (light grey) circles. Individuals depicted
here, or their guardians, gave signed consent for their likenesses to be published in this article. See the online
article for the color version of this figure.

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337FLEXIBLE RETRIEVAL AND FALSE MEMORIES

The critical comparison concerns the proportions of false mem-
ories on the detail/source tests given before versus after the asso-
ciative inference test, for correct compared with incorrect associa-
tive inference trials (i.e., AC). We distinguish among three
competing hypotheses:

(1) If recombination during retrieval both enhances associative
inference performance and also increases susceptibility to false
memories, then the proportion of false memories should be higher
for correct than incorrect inference trials, but only when the
detail/source test is given after the associative inference test (dur-
ing which recombination occurs); there should be no difference in
the proportion of false memories for correct versus incorrect
inference trials when the detail/source test is given before the
associative inference test.

(2) If the proportion of false memories is higher for correct than
incorrect inference trials both when the detail/source tests are
given before and after the associative tests, then these effects
would be attributable to integrative encoding processes.

(3) If there is no link at all between source memory misattribu-
tions and associative inference, then there should be no difference
between the proportion of false memories for correct and incorrect
inference trials regardless of when the detail/source test is given.

To test these hypotheses, and determine the reliability of the
results across variations in procedure and experimental parameters,
we conducted three initial experiments that used the same basic
paradigm and differed only in methodological details. Experiment
1 used a 24-hr study-test delay and a two-alternative forced choice
on the associative inference test, whereas Experiment 2 used a
48-hr study-test delay and included an additional “neither” option
on the forced-choice test (see Experiments 1 and 2 for rationale
regarding these changes). In Experiment 3, we increased the delay
between the directly learned (AB and BC) and associative infer-
ence trials (AC) on the one hand, and the second set of detail and
source questions on the other, to assess the durability of the effects
observed in Experiments 1 and 2. All three of these experiments
provided evidence in favor of the first hypothesis outlined previ-
ously: The proportion of false memories was higher for correct
than for incorrect inference trials, and only when the detail/source
test was given after the associative inference test, during which
recombination occurs. These findings implicate recombination
during retrieval in both associative inference and memory misat-
tribution, in line with the constructive episodic simulation hypoth-
esis. To further test the hypothesis, in Experiment 4 we eliminated
tests of directly learned associations (AB and BC), which in theory
could have contributed to the effects that we attributed to flexible
recombination. However, Experiment 4 again replicated the major
findings of Experiments 1–3, providing further evidence that re-
combination during retrieval is responsible for the observed pat-
tern of false memory effects.

Experiments 1 and 2

Because Experiments 1 and 2 used nearly identical procedures
with only minor differences, we report the methods and results for
these experiments together. To provide an overview of the basic
procedure, participants came to the lab for two sessions, separated
by a 24-hr (Experiment 1) or a 48-hr (Experiment 2) delay. The
delay in Experiment 2 was extended from 24- to 48-hr to more
closely replicate accuracy levels on the directly learned and asso-

ciative inference test reported in the standard associative inference
paradigm designed by Preston and colleagues (Preston et al., 2004;
Zeithamova, Dominick, & Preston, 2012; Zeithamova & Preston,
2010; Zeithamova, Schlichting, & Preston, 2012). Participants
completed a modified version of an associative inference paradigm
based on prior studies by the Preston group (Preston et al., 2004;
Zeithamova, Dominick, & Preston, 2012; Zeithamova & Preston,
2010; Zeithamova, Schlichting, & Preston, 2012). In the first
session, participants intentionally encoded directly learned associ-
ations between individual “A” and object “B” followed by a
second set of images with overlapping associations between object
“B” and individual “C” (Figure 1); participants were also pre-
sented with nonoverlapping X-Y individual-object pairs to reduce
performance for directly learned associations below ceiling levels.
A total of 24 ABC triads and 24 XY pairs were used in the
experiment. In the second session, participants were tested on
directly learned associations (i.e., AB, BC, XY) and associative
inference trials consisting of novel combinations of person pair-
ings (i.e., AC). In addition, for one half of the ABC triads,
participants answered 10 detail and source monitoring questions
per triad before they were tested on directly learned and associa-
tive inference trials. For the alternate half of the triads, participants
answered these detail and source monitoring questions after the
directly learned and associative inference trials for all items. As
noted earlier, the contrast between performance on the detail and
source memory tests given before compared with after the directly
learned/associative inference trials is critical to testing the three
key hypotheses we outlined.

Method

Participants. For both experiments, participants were re-
cruited via advertisements at Boston University and Harvard Uni-
versity. All had normal vision and no history of neurological
impairment. They gave informed consent, were treated in accor-
dance with guidelines approved by the ethics committee at Har-
vard University, and received either course credit or pay for
completing the study. Experiment 1 included 26 young adults
(mean age � 21.20, SD � 2.19; 15 women). Two participants
were excluded from the true, false, and foil memory analyses
because they were 100% accurate on the associative inference
trials; thus, our final sample consisted of 24 participants. Partici-
pants who were 100% accurate on the associative inference trials
were removed from the true, false, and foil memory analyses
because they did not have any trials for which they correctly
recalled the directly learned relationships and incorrectly inferred
the relationship between item A and item C, thereby precluding
meaningful comparisons of successful inference to unsuccessful
inference both before and after flexible retrieval. Experiment 2
included 25 young adults (mean age � 20, SD � 1.93; 14 women).
One participant was excluded from all analyses for having prior
experience with several of the task stimuli; thus, our final sample
consisted of 24 participants. Prior to the experiment, we decided
on a sample size of 24 based on previous work utilizing a similar
source monitoring paradigm (Okado & Stark, 2005). We stopped
data collection after reaching the target of 24 participants with
analyzable data.

AB and BC encoding. All experimental sessions were exe-
cuted on an Apple desktop computer using PsychoPy2 (v1.80.03).

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338 CARPENTER AND SCHACTER

Stimuli consisted of 72 still color images depicting everyday life
events (e.g., walking to work). Color images of common objects
(e.g., toy truck) and individuals were superimposed on outdoor and
indoor scenes. Scenes were counterbalanced across participants
such that each scene was used equally often for both AB and BC
pairs. Using Adobe Photoshop CC 2015, 48 overlapping pairs (24
AB pairs, 24 BC pairs—24 total ABC triads) and 24 unique,
nonoverlapping pairs (XY) were constructed. Overlapping AB and
BC pairs were constructed such that two individuals (A and C)
shared an association with an overlapping object (B; i.e., one ABC
triad). XY pairs were constructed of unique individual— object
pairs that did not share an overlapping association with other
pairings.

Participants received one of two versions of the AB encoding
task, which consisted of 36 images (i.e., AB and XY) followed by
the corresponding BC encoding task, which consisted of 36 images
(i.e., BC and XY; Figure 1). Each image was randomly presented
for 10 seconds within each encoding block (i.e., AB encoding and
BC encoding). Participants were instructed to learn both the direct
associations (i.e., AB, BC) and the indirect associations (i.e., AC)
along with the contextual information presented. Following each
image, participants were asked to provide a judgment of learning
on a scale from 1 to 4 (1 � definitely forget, 4 � definitely
remember). These judgments were collected to ensure participants’
attention during the encoding phase.

Detail and source monitoring. Ten detail and source moni-
toring questions were constructed for each of the 24 ABC triads (5
questions related to image AB and 5 questions related to image
BC). Detail questions were directly related to background details
that were present but contradictory in the AB and BC scenes and
did not reference the overlapping “B” object (Figure 1). A cutout
of the cue individual (i.e., either “A” or “C”) was presented to the
right of each detail question to indicate which scene the question
was referring to (Figure 1). For each detail question, participants
were given three options: the correct item, a misinformation
item, and an unrelated foil item. The misinformation item
consisted of information from the overlapping image in the triad
(e.g., if the detail question were related to the AB image, the
misinformation item would be a contradicting detail from the
BC image, such as a brown couch when a white couch had
appeared in the AB image). Foil items were details that were not
presented in either of the overlapping images (e.g., gray couch).
Following each detail question, participants indicated where
they remember seeing this contextual detail (i.e., the source of
the information; Figure 1). Participants were given four possi-
ble answer choices: (a) the first set of images—AB, (b) the
second set of images—BC, (c) both sets of images, or (d)
unsure. Immediately following participants’ source monitoring
response, they were asked to rate their confidence in their
response on a scale from 1 to 4 (1 � very unsure, 4 � very
sure). The presentation order of each set of questions (i.e.,
detail, source, confidence) was randomized for each participant
and the questions were self-paced.

Participants answered the 10 detail and source monitoring ques-
tions for one half of the 24 ABC triads before being tested on the
directly learned and associative inference trials. After participants
were tested on the directly learned and associative inference trials,
they completed the 10 detail and source monitoring questions for
the alternate half of the 24 ABC triads.

Directly learned and associative inference trials. Following
the first half of the detail and source questions, participants were
tested on directly learned (AB and BC) and associative inference
trials (AC). During each directly learned trial, a single cue indi-
vidual (e.g., an “A” or “C” individual) was presented at the top of
the screen and two choice objects were presented at the bottom of
the screen (e.g., two “B” objects from different ABC triads; Figure
1). On the associative inference trials, a cue individual (A) was
presented along with two individuals at the bottom of the screen
(i.e., the correct “C” individual from the ABC triad and a lure …