Examining Recall Memory in Infancy and Early Childhood Using the Elicited Imitation Paradigm

Summary

The elicited imitation procedure was established to examine the development of recall memory in infancy and early childhood. This procedure has been widely used to establish a solid foundation of the nature of recall memory in infancy and early childhood.

Abstract

The ability to recall the past allows us to report on details of previous experiences, from the everyday to the significant. Because recall memory is commonly assessed using verbal report paradigms in adults, studying the development of this ability in preverbal infants and children proved challenging. Over the past 30 years, researchers have developed a non-verbal means of assessing recall memory known as the elicited or deferred imitation paradigm. In one variant of the procedure, participants are presented with novel three-dimensional stimuli for a brief baseline period before a researcher demonstrates a series of actions that culminate in an end- or goal-state. The participant is allowed to imitate the demonstrated actions immediately, after a delay, or both. Recall performance is then compared to baseline or to performance on novel control sequences presented at the same session; memory can be assessed for the individual target actions and the order in which they were completed. This procedure is an accepted analogue to the verbal report techniques used with adults, and it has served to establish a solid foundation of the nature of recall memory in infancy and early childhood. In addition, the elicited or deferred imitation procedure has been modified and adapted to answer questions relevant to other aspects of cognitive functioning. The broad utility and application of imitation paradigms is discussed, along with limitations of the approach and directions for future research.

Introduction

The importance of recall memory cannot be overstated: this ability allows humans to report on mundane aspects of their day, such as what happened at their dentist appointment that morning, as well as their most significant life events, such as their wedding day or the day their child was born. Understanding the development of this ability is complicated, however, in that the verbal report methods used to examine recall memory in adults cannot be employed in studies with preverbal infants and children. For this reason, researchers developed a behavioral method known as elicited or deferred imitation to study recall memory before infants and children can discuss the past using language. This manuscript describes the procedure for implementing one version of the elicited or deferred imitation procedure with infants and children from 6 to 24 months of age. The described procedure is unique in that it that allows for the assessment of memory for the individual components of events as well as memory for temporal order information.

Piaget was among the first to indicate that deferred imitation was an index of representational ability.¹ He based this conclusion in part on observations of his own children. For instance, Piaget reported that his 16 month-old daughter, Jacqueline, re-enacted a tantrum that she had seen demonstrated approximately 12 hr earlier by a friend. Importantly, Jacqueline imitated the event in the absence of her friend and after a relatively lengthy delay. For these reasons, Piaget reported that Jacqueline must have encoded and maintained a representation of the event so that she could re-enact it after a delay, in the absence of ongoing perceptual support for what she had witnessed earlier. Based on this observation and others, Piaget stated that the ability to recall the past emerged in the second year of life, as children were concurrently developing the ability to engage in symbolic representation (as evidenced by advances in language and pretend play).

More recently, the elicited or deferred imitation procedure has been standardized and is now extensively used to study recall memory and related abilities in preverbal and early-verbal children. In the procedure developed by Patricia Bauer,^2,3 participants interact with three-dimensional materials used to create a novel sequence of events for a brief baseline period. A researcher then demonstrates how to complete the sequence of events, oftentimes with narration. Either immediately (immediate imitation) or after a delay ranging from minutes to months (deferred imitation), the participant is allowed the opportunity to imitate. The data are coded to determine whether the child performs (a) the demonstrated actions and (b) whether they are produced in the correct temporal order relative to baseline or relative to novel control sequences presented at the same session (see reference⁴ for additional information). Comparable but distinct imitation procedures have been developed and used by other researchers, including Andrew Meltzoff⁵ and Harlene Hayne.^6,7

Multiple arguments have been proposed to indicate that the type of memory assessed in the elicited or deferred imitation procedure is declarative or explicit in nature (instead of non-declarative or implicit; see reference⁸ for information on the multiple memory systems perspective). Although an exhaustive list of relevant arguments can be found in other sources,^9-14 three of the primary points are provided here. One indication that the type of memory being assessed is explicit or declarative in nature is that children talk about events that were experienced behaviorally in the context of the imitation procedure once they gain access to language;^15,16 because implicit or non-declarative memories cannot be accessed using language, evidence of later verbal accessibility strongly suggests that the type of memory under investigation is declarative or explicit. Another argument is that individuals with damage to the medial temporal lobe¹⁷ or the hippocampus¹⁸ are impaired on age-appropriate imitation tasks. Because declarative or explicit memories rely on the functioning of the hippocampus and associated medial temporal lobe structures,¹⁹ evidence of reduced performance by individuals with brain damage to these regions suggests that the type of memory assessed is declarative or explicit. The third argument to indicate that imitation assesses recall memory in particular is that there is no perceptual support available to cue memory for temporal order information.¹³ Although the sequence materials themselves might serve to cue recall for individual target actions, the props used to complete the event provide no useful information as to the temporal order in which the target actions must be completed. As such, temporal order information must be encoded upon event demonstration and maintained over time. For these reasons, the elicited imitation procedure is commonly regarded as the gold standard for studying recall memory in preverbal and early-verbal infants and children (see references^{10,13,14,20-22}).

Use of the elicited imitation procedure has provided a strong foundation for understanding advances in recall memory over the first three years of life. As discussed in previous reviews,^4,23,24 developments in recall are evident in the duration of time over which memories are retained and in the robustness of established memories. In terms of duration, researchers have indicated that 6-month-old infants recall one step of a 3-step event sequence for up to 24 hr.^6,25 By the time infants are 9 months of age, they remember the individual target actions that comprise a 2-step event sequence for 1 month.^26,27 Memory for temporal order information is less robust, such that only approximately 50% of infants remember the order in which a 2-step sequence was previously demonstrated. When infants are 10 months of age, memory for individual target actions is retained for 6 months and temporal order information is maintained for 3 months.²⁷ Only 10 months later, when children are 20 months of age, evidence of memory for temporal order information is apparent over durations of 12 months (and may even be evident for longer – 12 months was the longest duration over which the participants tested²⁸).

When considering the robustness of recall, age-related changes are apparent in the number of exposures required to support retention and in the ability to flexibly apply learned information. For example, 6-month-olds require as many as 6 exposures to evidence memory over a 24 hr delay,⁶ whereas 20 month-olds need only one exposure to demonstrate recall after 1 month.²⁹ In terms of representational flexibility, 12 month-olds do not generalize their learning across exemplars that only differ in color. Eighteen month-olds generalize their learning across cues that differ only in color, but do not demonstrate generalization when novel exemplars differ in both color and form. At 21 months, however, generalization across cues is more robust, such that children flexibly apply their learning to novel exemplars that vary on both dimensions.⁷ Moreover, research suggests that generalization is not born of forgetting: children retain information about the specific features of the original events as they flexibly apply their learning in new situations.^30,31

The goal of this manuscript is to describe the elicited imitation procedure developed by Bauer in detail. The method described herein is unique in that the procedure allows for assessment of both memory for individual actions demonstrated by the researcher as well as memory for temporal order. As indicated previously, it is important to note that there is no perceptual information present within the individual props to cue the order in which the specific actions should be completed. Therefore, memory for pairs of actions completed in the correct temporal order is a more stringent test of recall relative to reproduction of individual target actions.

The three-dimensional stimuli used in the elicited imitation procedure are commonly created from commercially-available toys or constructed out of plastic and/or wood. The stimuli depict events that are either novel to the participants (such as making a gong or a merry-go-round) or events with which children may have had previous experience (such as feeding a baby or putting a teddy bear to bed; see references^2,3,32 for studies that compare mnemonic performance on familiar versus novel events). Event sequences are further classified as being constrained by enabling relations, having arbitrary associations, or are mixed, such that they include some steps that are linked by enabling relations and others that are arbitrary in nature. Steps of sequences constrained by enabling relations must be completed in a specified temporal order for the sequence end-state to become apparent (although the sequences must be constructed so that children can perform all of the actions in any order). Figure 1 shows a three-step event sequence that is constrained by enabling relations.³³ For studies with children younger than 20 months of age, sequences constrained by enabling relations are most often utilized, as children of these ages demonstrate chance performance (i.e., completing fewer than 50% of the demonstrated pairs of actions on sequences with arbitrary associations;³⁴ see references^{2,28,32,35-37} for studies that compare mnemonic performance on events with different sequence constraints).

Figure 1: Example of the Three-step Enabling Event Sequence Make a Shaker. The left panel shows the first step of putting the block into one of the nesting cups; the middle panel shows the second step of assembling the nesting cups; the right panel shows the third step of shaking the assembled apparatus. The target actions must be performed in the correct temporal order for the sequence end-state to be realized, although the sequence materials are constructed so that the actions can be completed in any order. Figure and portions of the caption reproduced with permission from references.^33,42 Please click here to view a larger version of this figure.

The elicited imitation procedure is most frequently used with infants and children ranging in age from 6 to 24 months (although methodological alterations can be made to accommodate the testing of older children and adults^17,18). Typically developing or control participants are commonly recruited so that they are born at term (38 ± 2 weeks) and have not experienced any pre- or perinatal conditions that might negatively impact brain development and recall memory, as conditions such as preterm birth^38,39 and gestational diabetes^40,41 have been associated with reduced recall. In addition, researchers should be aware of the native language of the participants^33,42 if verbal labels will be used during sequence demonstration or as retrieval cues.

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Protocol

The administration instructions provided here are similar to those that have been approved previously by the Institutional Review Board at the University of California, Irvine.

1. Equipment

1. Test participants in a child-safe room that has an adult-sized table with three chairs (one for the researcher, one for the parent, and one for the child). Alternatively, test children in their homes at their own table or on a portable table provided by the researchers.
2. Use a video camera placed on a tripod to record the child (audio and video) as he/she participates in the study. Place the video camera so that the recording clearly shows the participant and the object of his/her gaze as well as each of the completed target actions.

2. Testing Procedures

1. Warm-up
   1. Seat the child directly across from the researcher at the adult-sized table. Sit children younger than 13 months old on the lap of a parent. Sit older children on a booster seat that is attached to an adult-sized chair unless they request to sit on the parent's lap. If the child is seated in a booster seat, sit the parent at the table next to the child.
   2. Engage the child in play with age-appropriate toys unrelated to the study so as to establish comfort with the researcher and the testing environment. Next, show children younger than 13 months old how to put a shape into the top or the side of a commercially-available shape sorter toy while narrating the action by saying, "Put it in."^26,27,43-45 Give older children a plastic ball and Slinky. Roll the ball across the table while saying "Roll it" and then put the ball inside of the Slinky while saying, "Put it in."
   3. Conduct each demonstration twice in succession before allowing the child the opportunity to imitate.
   4. Proceed once the child has interacted and shared toys with the researcher.
2. Baseline
   1. Put the sequence materials for the first event on the table; ensure that the same standardized order is used across participants.
   2. Push the props towards the child while providing a general verbal prompt to encourage interaction with the sequence materials, such as, "What can you do with this stuff?".
   3. Provide positive reinforcement as the child interacts with the props, both when he/she performs the target actions and when he/she is engaging with the sequence materials more generally. For example, say, "Good job!" or "That's a neat idea!" as the child explores the props. If the child does not interact with the first sequence at baseline, repeat Section 2.1.2.
   4. If the child appears distracted, call his/her name or tap on the sequence materials in an attempt to redirect his/her attention to the task.²⁸ Ensure that the props are not tapped in a manner that is suggestive of target actions or the order of their completion. Avoid use of phrases that suggest temporal order information, such as "What do you do next?" or "Then what?".
   5. Allow children younger than 13 months between 1½ and 2 minutes to interact with the props.^26,27,43-45 Terminate the baseline period for older children when the child engages in repetitive or off-task behaviors such as mouthing the props, repeatedly banging them on the table, or dropping them on the floor.^28,31,33,42 Model each sequence immediately after the baseline phase of testing for that sequence is terminated.
3. Sequence Modeling
   1. Bring the sequence materials back to the researcher's side of the table.
   2. Return the sequence materials to their original, standardized positions in the researcher's lap (so the child cannot see what the researcher is doing) and put them back on the table.
   3. Make eye contact with the child. Provide him/her with the name of the sequence using infant-directed speech. For example, for the event Make a Shaker, say, "I can use this stuff to Make a Shaker. Watch how I Make a Shaker with this stuff."
   4. Perform each target action with narration. For the event Make a Shaker, put the block into one of the two nesting cups while saying, "Put in the block." Cover one of the nesting cups with the other while saying, "Cover it up." Shake the assembled apparatus while saying, "Shake it!".
   5. Put all of the props back on the table, make eye contact with the child, and say, "That's how I Make a Shaker with this stuff!".
   6. Ensure that the child watches the researcher complete each of the demonstrated actions. If the child appears distracted, see Section 2.2.4.
   7. Return the sequence materials to their original positions as indicated in Section 2.3.2.
   8. Re-model the actions required to complete event sequence one more time (2 demonstrations total) as indicated in Sections 2.3.3, 2.3.4, 2.3.5, and 2.3.6.
   9. If immediate imitation is not permitted, repeat Sections 2.2, 2.3, and 2.4 for each of the remaining event sequences in turn.
4. Immediate Imitation
   1. Bring the sequence materials back to the researcher's side of the table.
   2. Return the sequence materials to their original, standardized positions (so the child cannot see what the researcher is doing) and put them back on the table.
   3. Push the props towards the child while providing the name of the event sequence as a retrieval cue. For example, when testing immediate imitation for Make a Shaker, say, "You can use this stuff to Make a Shaker. How do you Make a Shaker just like I did?".
   4. Allow children younger than 13 months old between 1½ and 2 minutes to interact with the props.^26,27,43,44 Terminate the imitation period for older children when the child engages in the repetitive or off-task behaviors listed in Section 2.2.5.^28,31,33,42
   5. Provide positive reinforcement as the child interacts with the sequences as indicated in Section 2.2.3.
   6. Repeat Section 2.2.4 if the child appears distracted during the imitation period.
   7. If immediate imitation is permitted, repeat Sections 2.2, 2.3, and 2.4 for each of the remaining event sequences in turn.
5. Additional Re-exposure Sessions (After Delays of Days to Weeks)
   1. Complete the warm-up procedure described in Section 2.1.2.
   2. Re-model the included event sequences as described in Section 2.3.
   3. If immediate imitation is permitted, complete the immediate imitation procedure as described in Section 2.4. If immediate imitation is not permitted, allow the child to play with commercially-available distracter toys between sequence demonstrations so as to maintain his/her interest in the task.^26,28,43,46
   4. Repeat Sections 2.5.2 and 2.5.3 for each of the remaining event sequences in turn.
6. Delayed Recall
   1. Complete the warm-up procedure described in Section 2.1.2.
   2. Put the sequence materials for the first event on the table; ensure that the same standardized order is used across participants and sessions.
   3. Push the props towards the child while providing the name of the event sequence as a retrieval cue. For example, when testing delayed recall for Make a Shaker, say, "You can use this stuff to Make a Shaker. How do you Make a Shaker with this stuff?".
   4. Allow children younger than 13 months old between 1½ and 2 minutes to interact with the props.^26,27,43-45 Terminate the imitation period for older children when the child engages in the repetitive or off-task behaviors listed in Section 2.2.5.^28,31,33,42 Participants may or may not reproduce the demonstrated target actions during the delayed recall period.
   5. Provide positive reinforcement as the child interacts with the sequences as indicated in Section 2.2.3.
   6. Repeat Section 2.2.4 if the child appears distracted during the delayed recall period.
   7. Repeat Sections 2.6.2 through 2.6.6 for each of the remaining event sequences in turn.
7. Data Coding and Reduction
   1. Create coding rules for each event. The coding rules sheet includes description of when the child receives credit for completing an action and when credit is not awarded. Award credit when the child achieves the action demonstrated by the researcher or when the child clearly attempts to complete the action (intention can be determined in part by watching the child's gaze). Importantly, in all cases, write coding rules so that the child can complete the target actions in any order.
   2. Create a data coding sheet that lists each of the included event sequences and the possible steps for each event.
   3. Have research assistants code videos that have been previously coded by the principal investigator or a senior lab member.
   4. While watching the videos, circle each target action completed by the child in the temporal order in which the actions are produced.
   5. Compare the codes by assigning a plus to each agreement and a minus to each disagreement. Train research assistants up to a reliability criterion of at least 90% on three consecutive participants before allowing them to code the study data.
   6. Compute the overall reliability by dividing the total number of agreements to the total number of codes. More commonly, reliability is coded by counting only the first occurrence of each coded action so as to reduce the likelihood of receiving credit for actions performed by chance or trial-and-error.^{26-28,31,33,42-45}
   7. Have the trained coder score the remaining videos or have the tester code the data as they are collected (recommended only when participants are 13 months or older^29,31).
   8. Reduce the data to determine the number of target actions and pairs of actions produced for each event at each phase of testing (for example, baseline, immediate imitation, and delayed recall). Only the first occurrence of each target action is commonly considered during data reduction so as to reduce the likelihood of awarding credit for actions produced by chance or trial-and-error.²⁸ Count the number of unique target actions that were coded by sequence (for example, a participant would receive a score of 3 target actions if he/she produced the following sequence of actions: 3-1-2-3).
   9. Count the number of pairs of actions completed by sequence when considering only the first time each target action was completed (for example, a participant would receive a score of 1 pair of actions if he/she produced the following sequence of actions: 3-1-2-3; a participant would also receive a score of 1 pair of actions if he/she produced the following sequence of actions: 1-3-2-1).
      Note: The maximum number of target actions possible is the total number of steps in the sequence, whereas the maximum number of pairs of actions is the maximum number of target actions possible minus one.
   10. Create averages indicating the number of target actions performed at each phase of testing (baseline, immediate imitation, and delayed recall, for example), and for each condition (if applicable).
       Note: The elicited imitation procedure is administered and scored in the same way whether researchers use sequences with enabling, mixed, or arbitrary associations.²⁸

Figure 2: Sample Data Coding Sheet for the Three-step Enabling Event Sequence Make a Shaker. The three target actions ("Put it in," "Cover it up," and "Shake it") are shown multiple times for each of three phases of testing (baseline, immediate imitation, and delayed recall). Space is also provided to record the number of target actions and pairs of actions completed at each phase. Please click here to view a larger version of this figure.

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Results

A recent elicited imitation study examined whether child language comprehension moderated the relation between the use of supportive adult language at sequence demonstration when recall was assessed behaviorally at encoding (immediate imitation) and at delayed recall 1 week later.³³ Sixteen month-old children were presented with 6 novel 3-step event sequences that were constrained by enabling relations. After a brief baseline period, a researcher demonstrated each of two event ...

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Discussion

Over the past 30 years, many researchers have used elicited or deferred imitation procedures to examine the development of recall memory in infancy and early childhood. One advantage of imitation procedures is that they are highly versatile: as such, they can be modified and adapted to answer various questions relevant to cognitive development. For example, the elicited imitation procedure has been administered in combination with electrophysiological indices of recognition memory so as to examine relations between encod...

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Materials

Name	Company	Catalog Number	Comments
Camcorder	Canon	VIXIA HF R600 HD Flash Memory Camcorder	Any commercially-available camcorder that records in color and has audio will suffice