Integrating across episodes: Investigating the long-term accessibility of self-derived knowledge in 4-year-old children

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Highlights

  • Knowledge derived through cross-episode integration was retained by 4-year-olds.

  • Cues after a delay enhanced the accessibility of previously derived knowledge.

  • Cues after a delay enabled extension of knowledge not initially derived.

  • Cross-episode knowledge is available to post-encoding growth over a 1-week period.

Abstract

Semantic memory, defined as our store of knowledge about the world, provides representational support for all of our higher order cognitive functions. As such, it is crucial that the contents of semantic memory remain accessible over time. Although memory for knowledge learned through direct observation has been investigated previously, we know very little about the retention of knowledge derived through integration of information acquired across separate learning episodes. The current research investigated cross-episode integration in 4-year-old children. Participants were presented with novel facts via distinct story episodes and tested for knowledge extension through cross-episode integration as well as for retention of the information over a 1-week delay. In Experiment 1, children retained the self-derived knowledge over the delay, although performance was primarily evidenced in a forced-choice format. In Experiment 2, we sought to facilitate the accessibility and robustness of self-derived knowledge by providing a verbal reminder after the delay. The accessibility of self-derived knowledge increased irrespective of whether participants successfully demonstrated knowledge of the integration facts during the first visit. The results suggest that knowledge extended through integration remains accessible after delays even in a population where this learning process is less robust. The findings also demonstrate the facilitative effect of reminders on the accessibility and further extension of knowledge over extended time periods.

Introduction

To build a knowledge base, it is necessary to integrate information learned across separate episodes of experience. We regularly integrate information learned at different times, in different contexts, and through different media. For instance, in an early episode, an individual may learn that George Washington was the first president. In a later episode, perhaps in the context of a history class, the individual may then learn that George Washington led the Continental Army during the American Revolution. Integration of the two distinct traces may support self-generation of new knowledge that the leader of the American Revolution was also the first president, an understanding not directly specified. As this example demonstrates, knowledge extension through memory integration is pervasive, allowing for the combination of newly and previously learned information. Without this capacity, knowledge development would be significantly hindered if not impossible. Yet the apparent ease with which we link related information in memory to form new knowledge (as many of us have seamlessly done with respect to George Washington) often leads us to take this ability for granted. In fact, systematic investigations of cross-episode integration have only recently appeared in the literature (e.g., Bauer & San Souci, 2010). As a consequence, although we know a great deal about the long-term retention of information learned through a single direct experience (e.g., Bauer et al., in press, Ornstein et al., 1998), we know very little about the later accessibility of knowledge derived through cross-episode integration. To address this issue, in the current research we examined whether knowledge extended through integration is retained in preschool-age children (Experiment 1). Because this is a population in which knowledge extension through integration is less robust (e.g., Bauer and San Souci, 2010, Bauer et al., 2015), we also examined whether cues aimed to reinstate prior learning episodes would facilitate the later accessibility of self-derived knowledge (Experiment 2).

The question of how knowledge emerges from experience has been disputed for decades (e.g., Karmiloff-Smith, 1986, Karmiloff-Smith, 1990, Mandler, 1988, Mandler, 1992, Nelson, 1974, Piaget, 1972). For example, proponents of the core knowledge perspective argue that infants are born with a set of innate concepts and that this foundational knowledge provides the essential elements for learning and reasoning about one’s experiences (e.g., Spelke, 2004, Spelke and Kinzler, 2007). On the other end of the spectrum, proponents of constructivist perspectives (e.g., Piaget, 1972) argue that all knowledge is actively constructed through one’s direct experience in the world (for reviews, see Greeno, Collins, & Resnick, 1996, and Packer, 1985). In spite of this range of perspectives regarding the role of experience, until recently the empirical study of general knowledge acquisition (i.e., semantic memory) and of memory for previous experiences (i.e., episodic memory) has been largely separate (Tulving, 1972). Nonetheless, prior research makes clear that as knowledge becomes increasingly integrated in memory, the capacity for flexible knowledge extension is more readily observed (Chi et al., 1989, Chi and Koeske, 1983). For example, child expertise in the domain of dinosaurs is marked by extensive integration of shared properties (e.g., habitat, defense mechanisms) that results in hierarchically organized knowledge structures (i.e., into families such as tyrannosaur and stegosaur). Although the episodes in which children initially integrated this information were not examined, the benefits of knowledge integration are readily apparent. Specifically, when children were asked to extend their knowledge in order to make inferences about dinosaurs they had never seen before, child experts were able to use their integrated knowledge to generate sophisticated conclusions based on non-observed properties (e.g., this dinosaur must have a plant-based diet). In contrast, novices ascertained only surface-level observable properties (e.g., this dinosaur can fly) and generated significantly fewer accurate conclusions (Chi et al., 1989).

Given the importance of developing an integrated knowledge base, a growing body of literature has begun to examine the ability to integrate information acquired across separate episodes of experience (Bauer et al., 2015, Bauer et al., 2012, Bauer and San Souci, 2010, Varga and Bauer, 2013). In this line of work, children are taught novel facts (i.e., stem facts) that can be combined to generate new knowledge. For instance, two facts about dolphins (e.g., Dolphins talk by clicking and squeaking; Dolphins travel in groups called pods), can be integrated to produce new knowledge that was never directly learned (e.g., Pods talk by clicking and squeaking). Much like real-world learning conditions, children are required to extract these facts in the midst of dynamic episodes. Specifically, each fact is embedded within a separate story passage, thereby providing a means of observing integration across distinct experiences. To mirror standard episodes (see Tulving, 2002, for a review), each passage contains the uniquely defining elements of “what” (actions of main characters), “where” (story setting), and “when” (temporal connections throughout the ongoing narrative). To ensure that children encode each passage as a separate episode (e.g., Ezzyat & Davachi, 2011), clear event boundaries are incorporated into the narrative (i.e., a beginning, a middle, and an end). Furthermore, episodes are also temporally separated by the imposition of unrelated tasks between to-be-integrated passages. Importantly, when the degree of surface similarity between to-be-integrated passages was manipulated (i.e., the character was either the same or different between paired passages), knowledge extension through integration was less robust under low surface similarity conditions (Bauer, King, et al., 2012). This finding suggests that children perceive the passages as distinct episodes rather than as one large story-reading task; otherwise, performance would not have varied as a function of contextual detail.

Consistent with the developmental trajectory observed for other forms of knowledge extension, such as induction, deduction, and analogy (see Goswami, 2011, Goswami, 2013, for reviews), the capacity to generate knowledge through cross-episode integration increases over the preschool and early school years. When 4-year-old children are asked open-ended questions that prompt self-generation through integration (e.g., How does a pod talk?), they generate the novel understanding only 13% of the time. In contrast, 6-year-olds demonstrate the capacity on 67% of the trials (Bauer & San Souci, 2010). When 4-year-olds are tested for knowledge extension via forced-choice questions, they approximate the higher level of performance by demonstrating knowledge of the integration facts on 62% of the trials.

Recent investigations have made great strides in characterizing knowledge extension through integration within a single session, yet there remain interesting questions about the long-term retention of self-derived knowledge. That is to say, in everyday learning contexts, delays between initial learning and later use are commonly experienced. Thus, for self-derivative processes to be psychologically, cognitively, and educationally meaningful, their products must be maintained over time. Although many researchers have acknowledged the growing need to examine self-derivative processes under conditions that better mirror everyday learning conditions (e.g., Gentner and Smith, 2012, Jee et al., 2010), the long-term retention of self-derived knowledge has received little attention in the literature. The current research was designed to address this gap.

In the first investigation of whether newly extended knowledge persists over time, Varga and Bauer (2013) found that 6-year-old children exhibit nearly perfect recall for knowledge derived through cross-episode integration. That is, immediately after exposure to passages of text in which they learn novel facts, 6-year-olds generate novel integration facts on 63% of trials. One week later, they recalled the self-generated facts on 60% of trials. The question in the current research was whether we would see retention in younger children, who demonstrate knowledge extension primarily in forced-choice testing. It is clear that preschool-age children remember information over time (for comprehensive reviews, see Bauer, 2007, Bauer et al., 2011, Lukowski and Bauer, 2013, Schneider, 2011). For example, 4- and 5-year-olds retain unique factual information acquired in a classroom setting over a 1-week period (Bemis, Leichtman, & Pillemer, 2013). Furthermore, 4-year-olds retain episodic memories for events that occurred during a prior week (Bauer et al., in press, Scarf et al., 2013), month (Bauer, Larkina, & Doydum, 2012), and year (e.g., Bauer & Larkina, 2014). Yet there are reasons to believe that 4-year-olds’ retention will not equal that of 6-year-olds. First, recall of directly observed events and explicitly taught information is less robust in preschool children compared with school-aged children both immediately and after delays (Baker-Ward et al., 1993, Bauer et al., 2012, Ornstein, 1995, Ornstein et al., 1998).

A second reason we might expect lower levels of retention of self-generated information in 4-year-olds relative to 6-year-olds is that knowledge extension through integration is less robust in younger children relative to older children (Bauer & San Souci, 2010). As a result, it is reasonable to expect that integrated memory representations might exhibit a different pattern of retention as compared with what has previously been shown for older children. As discussed previously, 4-year-olds exhibit almost floor levels of knowledge extension when tested in an open-ended format (e.g., How does a pod talk?). In contrast, they readily demonstrate knowledge of the integration facts when tested in a forced-choice format (e.g., by rubbing noses, by clicking and squeaking, or by cellphone). This pattern parallels that observed for explicitly taught or directly acquired information. That is, superior memory in forced-choice measures (in comparison with open-ended measures) is well documented in the literature (e.g., Haist, Shimamura, & Squire, 1992). The difference is particularly pronounced during the preschool years (e.g., Perlmutter and Myers, 1979, Perlmutter and Ricks, 1979). Forced-choice testing presumably permits accurate responding based on a weaker memory trace (see Squire, Wixted, & Clark, 2007, for a review). Moreover, younger children’s dependence on supported forced-choice conditions for demonstration of newly self-generated knowledge implies that their memory traces may be less robust and, thus, more vulnerable to loss over time. We tested this possibility in Experiment 1 by extending the work by Varga and Bauer (2013) to test whether 4-year-olds retain knowledge derived through cross-episode integration after a 1-week delay.

To anticipate the results of Experiment 1, 4-year-olds retained information self-derived through integration at Session 1 over the 1-week delay. Yet as expected, memory was expressed primarily through forced-choice measures rather than open-ended ones. In Experiment 2, we sought to facilitate the accessibility of knowledge after the delay by providing children with reminders after the delay. Specifically, we provided 4-year-olds with one of the two stem facts from a pair of to-be-integrated passages (e.g., Dolphins travel in groups called pods). We hypothesized that reminders of the explicitly taught facts would facilitate subsequent retrieval of previously extended knowledge. This hypothesis was based on three previous findings. First, a large body of research shows that reminders and reinstatements are a highly effective means of extending young children’s event memories over delays (e.g., Bauer et al., in press, Hudson and Fivush, 1991, Hudson et al., 2006). Second, 4-year-olds can effectively use verbal reminders to access information that appears to have been forgotten (e.g., Imuta et al., 2013, Morgan and Hayne, 2007). Third, and directly related to the current paradigm, the provision of hints has been shown to facilitate knowledge extension through integration by 4-year-olds within a single learning session (Bauer et al., 2015, Bauer et al., 2012). Moreover, these hints are maximally effective when cues correspond to specific episodes as well as when they are provided immediately before the test for knowledge extension (Bauer et al., 2015). Guided by these literatures, we predicted that the instantiation of a verbal stem fact reminder would reactivate the prior learning episode, thereby increasing the accessibility of previously extended knowledge.

Together, the current research contributes valuable insight into the retention and later accessibility of knowledge derived through cross-episode integration. For both experiments, we selected a delay of 1 week. This is a period of time over which other age groups have exhibited exceptional memory for self-derived knowledge (Varga & Bauer, 2013). We chose to focus the inquiry on 4-year-old children because this is an age group in which knowledge extension through cross-episode integration is less robust. As such, this is a population that would benefit from interventions aimed at facilitating this pervasive form of knowledge development.

Section snippets

Participants

Participants were 20 4-year-old children (8 girls and 12 boys, Mage = 4 years 5 months, range = 4 years 3 months to 4 years 9 months). They took part in two sessions spaced 1 week apart (Mdelay = 7.40 days, range = 7 to −9). An additional 3 children participated in the study but were excluded due to failure to return for the second session (n = 1) or experimental error (n = 2). Children were recruited from a volunteer pool consisting of families who had expressed interest in participating in research. Based on

Participants

Participants were 21 4-year-old children (15 girls and 6 boys, Mage = 4 years 6 months, range = 4 years 1 month to 4 years 9 months). They participated in two sessions separated by a delay of approximately 1 week (Mdelay = 6.86 days, range = 6–8). An additional 7 children participated in the study but were excluded from the final analysis due to failure to return for the second session (n = 3), failure to provide answers to the test questions (including the filler questions and the unrelated tasks) (n = 3), or

General discussion

The purpose of the current research was to investigate the long-term accessibility of knowledge newly derived through cross-episode integration. We expanded on prior research with school-age children (Varga & Bauer, 2013) by examining this question in 4-year-olds, a population in which this form of knowledge extension is less robust (e.g., Bauer & San Souci, 2010). We also expanded on prior investigations of knowledge extension by elucidating means of facilitating the accessibility of

Acknowledgments

This research was funded by the National Institutes of Health (NICHD, HD67359, to Patricia J. Bauer) and by the Emory College of Arts and Sciences. The authors thank Elizabeth A. White for her help with various aspects of the research. The authors also extend their appreciation to the children and families who participated in the research, without whom this work would not have been possible.

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