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You Can't Take It with You: The Translation of Memory across Development Author(s): Rick Richardson and Harlene Hayne Source: Current Directions in Psychological Science, Vol. 16, No. 4 (Aug., 2007), pp. 223-227 Published by: Sage Publications, Inc. on behalf of Association for Psychological Science Stable URL: http://www.jstor.org/stable/20183201 . Accessed: 24/09/2013 19:58 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. . Sage Publications, Inc. and Association for Psychological Science are collaborating with JSTOR to digitize, preserve and extend access to Current Directions in Psychological Science. http://www.jstor.org This content downloaded from 136.159.235.223 on Tue, 24 Sep 2013 19:58:44 PM All use subject to JSTOR Terms and Conditions

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Page 1: You Can't Take It with You: The Translation of Memory across Development

You Can't Take It with You: The Translation of Memory across DevelopmentAuthor(s): Rick Richardson and Harlene HayneSource: Current Directions in Psychological Science, Vol. 16, No. 4 (Aug., 2007), pp. 223-227Published by: Sage Publications, Inc. on behalf of Association for Psychological ScienceStable URL: http://www.jstor.org/stable/20183201 .

Accessed: 24/09/2013 19:58

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

.

Sage Publications, Inc. and Association for Psychological Science are collaborating with JSTOR to digitize,preserve and extend access to Current Directions in Psychological Science.

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Page 2: You Can't Take It with You: The Translation of Memory across Development

CURRENT DIRECTIONS IN PSYCHOLOGICAL SCIENCE

You Can't Take It With You

The Translation of Memory Across Development Rick Richardson and Harlene Hayne

University of New South Wales, Sydney, Australia, and Otago University, Dunedin, New Zealand

ABSTRACT?Despite evidence for memory skill early in de

velopment, the evidence reviewed here shows that early

acquired memories, in rats and humans, are frozen in time.

That is, in the absence of opportunities for updating, early memories are

only expressed via responses or words that

were available at the time of encoding. We discuss the

theoretical importance of these findings and their potential clinical and forensic implications.

KEYWORDS?memory; development; fear; language

While there is substantial evidence that infants of many species are

capable of learning and remembering, developmental

changes in these processes may limit access to early memories

later in life. In humans, most adults have little or no recollection

of events that occurred prior to the age of 3 or 4 years, a phe

nomenon called infantile or childhood amnesia. Similarly, in a

wide range of altricial (i.e., requiring parental care for some

period of time after birth) nonhuman species, information that is

learned during infancy is not expressed in adulthood. Why might

this be?

There are a number of changes in memory processing that may

contribute to the inability to recall events that occurred early in

development (Hayne, 2004). Studies with both human infants

and infant rats have shown that younger organisms encode in

formation more slowly than their older counterparts do. Thus, for

any given learning experience, a younger organism establishes

a leaner representation (i.e., with fewer details) than an older

organism does. Furthermore, even when the level of encoding is

held constant across age groups, younger organisms forget faster.

These age-related changes in encoding and retention may help

to explain why adults show little or no retention of their early

experiences.

Age-related changes in memory expression may also play a

role in infantile amnesia (Pillemer & White, 1989). Although human infants learn and remember, their memories are pre

Address correspondence to Rick Richardson, School of Psychology,

University of New South Wales, Sydney 2052, Australia; e-mail:

r. richardson@unsw. edu. au.

sumably stored in a nonverbal format. As adults, most of our

memories are stored, retrieved, and expressed using language.

In order for memories encoded during infancy to be verbally

expressed, we would need to translate our preverbal represen

tation into language at some point during development. Fur

thermore, the neural basis of memory is different in infants

than it is in adults (e.g., Nelson, 1995; Seress, 2001). Memory

processing early in development is supported by one neural

substrate, while later in development it is supported by another.

If memories encoded during infancy are retained over significant

periods of development, they must be transferred from one

substrate to the other.

In this article, we review recent research designed to assess the

long-lasting effects of specific learning experiences that occurred

early in development. We try to answer two fundamental ques

tions. First, "Do we take our memories with us as we grow and

change?" Second, "If we do, does the expression of those mem

ories change during development?" We review research con

ducted with both infant rats and infant humans. Despite obvious

differences between these two species, conclusions regarding

memory development in both are remarkably similar.

MEMORY DEVELOPMENT IN RATS

Psychologists have long been interested in how fears are learned

and maintained, in part, because many anxiety disorders may be

due to specific learning experiences that occurred early in de

velopment (e.g., Jacobs & Nadel, 1985; Mineka & Zinbarg,

2006). Understanding the basic processes involved in memory

for fear-eliciting stimuli may lead to the development of effective

treatments for anxiety disorders. Research with nonhuman an

imals provides the opportunity to study the fate of a memory for a fearful experience across the entire lifespan, and rats are the

most common subjects in research of this kind. The initial

memory is typically established using Pavlovian fear condi

tioning; animals are presented with an innocuous conditioned

stimulus (CS; e.g., an odor or a tone) that is paired with an

aversive unconditioned stimulus (US; e.g., a shock). Subsequent

presentations of the CS elicit a variety of fear-like behaviors.

Some of the most frequently measured fear responses include

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Page 3: You Can't Take It with You: The Translation of Memory across Development

Translation of Memory Across Development

freezing, changes in cardiovascular activity, and potentiated

startle responses to an unexpected, loud noise.

During development, behavioral indices of learned fear

emerge at different times. Specifically, freezing in response to a

CS previously paired with shock is observed at a younger age than are changes in heart rate, and changes in heart rate occur at

a younger age than potentiated startle (Hunt & Campbell, 1997). This sequential emergence of the behavioral components of

learned fear allows us to ask fundamental questions about the

translation and expression of memory across stages of develop

ment. Specifically, is learned fear expressed in a manner ap

propriate to the rat's age at the time of training or to its age at the

time of testing? If rats are trained at an age when they can ex

press learned fear via one response (e.g., freezing) but not some

other response (e.g., potentiated startle) and they are then tested

at a later age when they can express learned fear via both re

sponses, is the fear expressed through all the reactions available

to the animal at the time of test or is it expressed only by reactions

that were available at the time of training? When rats are trained on postnatal day (PND) 16 and tested

the following day, they exhibit freezing or avoidance to the

odor CS, but not a potentiated startle response to a loud, unex

pected noise in the presence of the CS. In contrast, rats trained

on PND22 and tested the following day exhibit freezing, avoid

ance, and potentiated startle in the presence of the CS. What

happens, however, when rats are trained on PND 16 and tested on

PND23? We have completed several studies that have explored this question (e.g., Richardson & Fan, 2002; Yap, Stapinski, &

Richardson, 2005). We have consistently found that rats do not

forget the CS-US association over the 1-week interval but that

they only express their learned fear via components of the fear

reaction that were available at the time of training. That is, they

freeze, but they do not exhibit potentiated startle (Fig. 1; see also, Barnet & Hunt, 2006). These results suggest that early-acquired

fear memories are not translated across development?at least

in terms of how they are

expressed?but are rather frozen in

time. In other words, early-acquired memories do not appear to

gain access to later-developing response systems. Although we

suspect that similar phenomena occur in other nonhuman

animals, to date, the issue has only been studied in rats.

MEMORY DEVELOPMENT IN CHILDREN

Although many of the basic memory processes exhibited by humans have been modelled in animals, our ability to encode,

retrieve, and express memories through language has no other

parallel in the animal kingdom. As adults, our receptive

language skills allow us to access memories very quickly;

sometimes only a few words are required to cue remarkably vivid

memories of past experiences, even when those experiences took

place a long time ago. Furthermore, our productive language

skills allow us to express our memories verbally, sharing

P16 P22 CS + US * test CS 24 hrs later CS + US * test CS 24 hrs later

Avoidance !2 Avoidance El Freezing S

Freezing 0 FPSS FPS0

P16 -? Test 1 week later *

P23

CS+US Avoidance E3

Freezing 0 FPS?

Fig. 1. Test of memory development in rats. Rats given pairings between a

conditioned stimulus (CS; in this case, an odor) and an unconditioned

stimulus (US; a shock) at 16 days of age (P16) express their learned fear of

the odor CS when they are tested 24 hours later through some behaviors

(e.g., avoidance, freezing) but not others (FPS; fear-potentiated startle). Rats trained at 22 days of age (P22) and tested 24 hours later express their

learned fear of the odor through all three behaviors. The critical finding is

that rats trained at 16 days of age and then tested at 23 days of age (P23) retain the odor-shock association across the 7-day interval, but they only

express their learned fear through response systems (i.e., avoidance and

freezing) that were mature at the time of training.

them with others who may or may not have shared our original

experience.

Although human infants exhibit rudimentary memory skills at

the time of birth and typically say their first word sometime around

their first birthday, their ability to use these two skills in concert

develops over a protracted period. Most children are fairly fluent

in their native language by about the age of four, but children this

age still have difficulty in verbally expressing their memories

(Simcock & Hayne, 2003). Given that the linguistic content of a

child's memory representation is likely to be very limited, verbal

recall of events that occurred during this period of development would require translation of the representation from a nonverbal to

a verbal format. Is there evidence that this occurs?

In our research, children participate in a unique experience

early in development, when their linguistic skill is extremely limited; they are then interviewed after a long delay, once their

language skills have improved. As in the infant-rat research

described earlier, we wondered whether children would express

their memory using all of the components available to them at the

time of the test (i.e., both verbal and nonverbal skills) or whether

their memory would be restricted to the components that were

available at the time of the original experience. The unique

experience is learning to operate a "Magic Shrinking Machine":

Two- to 4-year-old participants lift a lever, place a large object in

the machine, turn a handle, and retrieve a smaller but otherwise

identical object from a drawer at the front. (Shrinking is ac

complished by surreptitiously replacing the large object with a

smaller one.) After delays ranging from 1 day to 1 year, children's

verbal and nonverbal recall of the event is assessed (Simcock &

Hayne, 2002, 2003). During the verbal portion of the test, children are asked to describe what happened during the event;

during the nonverbal portion, they are asked to identify photo

graphs of the objects that were present and to reproduce the

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Page 4: You Can't Take It with You: The Translation of Memory across Development

Rick Richardson and Marlene Hayne

actions required to operate the machine. Children's receptive

and productive language skills are measured at the time of the

original event and at the time of the test.

Children of all ages exhibit nonverbal memory for this event

even when tested after a 1-year delay. Furthermore, verbal recall

increases as a function of age and language skill. More impor

tantly, children's verbal recall after a delay reflects their vo

cabulary at the time of original encoding rather than their

vocabulary at the time of the test. Although their language skills

improve dramatically overtime (i.e., 6- or 12-months), children's

verbal reports at the test contain only event-relevant words that

were part of their vocabulary at the time of the original event.

In no instance has a child in our research used a word or words

that were not part of his/her productive vocabulary at the time

of encoding. Thus, even though children's language skills

have improved over the delay and they have maintained non

verbal representations of the event, they do not map their new

language skills onto their existing memory representations

(see Fig. 2). In other words, children do not simply retrieve their

nonverbal representations of the event and tell verbal stories

about it. This same basic finding has been reported in other

studies in which children have been interviewed about more

emotional events, including trips to the emergency room (Howe,

Courage, & Peterson, 1994). These studies have also shown that

it is difficult (Cheatham & Bauer, 2005), if not impossible, for

children to map their new language skills onto their existing

nonverbal memory representations.

UPDATING OF EARLY MEMORIES

In the research described so far, participants are exposed to a

discrete event for a very brief period (e.g., a few minutes), and

they do not experience anything similar to that event during the

retention interval. While some early experiences may share

these characteristics, others would not. Some experiences may

occur over and over again. What happens to early memories if

the target event, or something similar, occurs repeatedly? Is the

original memory updated to reflect current environmental con

ditions or response patterns? Although we don't know for sure,

some of our recent research (Yap et al., 2005) suggests that such

updating may occur. For example, if rats are trained to fear one

odor at PND16 and then trained to fear a second, discriminably different odor at PND22, they express their fear of the first odor

via the potentiated startle response when tested at PND23. In

other words, these rats express their fear to the earlier-trained

CS by a response that has matured during the retention interval

(also see Barnet & Hunt, 2006). This result suggests that earlier

acquired nonverbal memories can be updated if they are

reactivated and re-encoded at later stages of development (see

Hartshorn & Rovee-Collier, 2003). Evidence regarding verbal updating of preverbal memories is

much more equivocal. For example, Peterson and Rideout

(1998) repeatedly interviewed children about a medical injury

they had suffered over a period of 18 to 24 months. At the time of

the injury, children ranged in age from 12 to 34 months. Older

children reported more information than younger children did

and the amount of information reported increased across

successive interviews. Importantly, although the youngest par

ticipants did not provide verbal accounts of their injuries at the

time that they happened, they did provide verbal accounts when

interviewed after a delay. Although it is possible that the

youngest participants translated their preverbal representations

into language as their language skills improved, it is also pos sible that, over time, children incorporated more of what they

had been told by others about the events into their own accounts.

That is, during the later interviews, children's reports may have

been updated and augmented to include other sources of infor

mation that they had encountered after their memories were

originally established. In this way, children's reports of their

earlier experiences would be based in part on their own episodic

memories for the events, but would also include secondhand

information that others had told them. We assume that children's

memories could be updated in a similar way by exposure to

photos or videos of the original event. In this case, what children

ultimately report may include information that was encoded

at the time the event took place as well as information that was

encoded on the basis of exposure to photos or video.

IMPLICATIONS

What are the implications of the data reviewed here? We propose

that, unless they are "updated," memories for discrete events that

occur very early in life are not translated across stages of devel

opment. Rather, these memories, if retained, are maintained in

the same representational format in which they were originally encoded. Therefore, these early memories are

expressed in a

manner quite different from the way in which they would be

expressed if acquired later in development. If we are correct,

the data outlined here have important implications in both clinical

and forensic contexts. From a clinical perspective, we would

predict that fears, phobias, and anxiety in adults that are due

to early discrete trauma may be expressed in a manner that is

more similar to the way in which young organisms express

their fear. We know that early-acquired memory representations

are leaner than memories acquired later in development, and

might therefore generalize more broadly (e.g., Jacobs & Nadel,

1985). Extrapolating from research with infants and children, we would also predict that individuals are unlikely to gain full,

explicit recollection of the original trauma. Given this, psycho

logical difficulties that originate from these kinds of early expe riences may be particularly difficult to treat because their effects

become entrenched in an individual's behavior and personality,

even though the fear-eliciting events cannot be recalled or

discussed.

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Page 5: You Can't Take It with You: The Translation of Memory across Development

Translation of Memory Across Development

Nonverbal

Memory

Representation

B Language

Acquisition

2 45 o o CO 40

| 35 -Q S^ 30 o

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Q. X LU

15'

Retention Interval

Photo Reenactment

Nonverbal Memory Measure

23

22

Li Encoding Test

Assessment

10

co 21

o 20

S 19 CD E? 18 03

r- 17

16

15' L_J?L Encoding Test

Assessment

CD

c5 r

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0 Photo Reenactment Verbal

Memory Measure

Fig. 2. Test of memory development in small children. Two-year-old children established a nonverbal memory representation (A; tested

through photo recognition and behavioral reenactment) of the magic shrinking machine and maintained some of that representation over a 1

year delay (top graph). Children's general language skills (Expressive Vocabulary) and their task-specific vocabulary (Target Words) increased

over that time period (B); by the time of the 1-year test, children had acquired most of the words that were required to describe the magic

shrinking machine. Despite this, children failed to map their new language skills onto their nonverbal representation of the target event (C).

Although at the 1-year test children recognized photographs (Photo) and performed actions (Reenactment) that had not been part of their

productive vocabulary at the time of original encoding, in no instance did a child use a word or words that had not been part of their productive

vocabulary at the time of original encoding to describe the event 1 year later.

From a forensic perspective, although traumatic events that

take place during early development undoubtedly leave their

mark, the finding that children do not readily translate their

early memories into language limits the probability that an in

dividual abused as an infant or very young child could provide a coherent verbal account of those experiences several years

later, particularly if the events have not been discussed in the

meantime (Hayne, 2006). Finally, from a developmental per

spective, the data reviewed here provide new clues to the age-old

mystery of childhood amnesia. We hypothesize that one reason

we do not recall much of our infancy and early childhood may be

that those memories were encoded in a fundamentally different

format. Because many of our early experiences are never re

peated, our memories for them are not retrieved or updated,

and these memories get left behind on our journey across

development.

Acknowledgments?This work was supported by Australian

Research Council Discovery grants to Rick Richardson

(DP0346139, DP0666953) and by a Marsden grant (UOO096) from the Royal Society of New Zealand to Harlene Hayne.

Recommended Reading

Barnet, R.C., & Hunt, P.S. (2006). (See References)

Hayne, H. (2006). (See References)

Yap, C.S.L., Stapinski, L., & Richardson, R. (2005). (See References)

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Page 6: You Can't Take It with You: The Translation of Memory across Development

Rick Richardson and Marlene Hayne

REFERENCES

Barnet, R.C., & Hunt, P.S. (2006). The expression of fear-potentiated startle during development: Integration of learning and response

systems. Behavioral Neuroscience, 120, 861-872.

Cheatham, C.L., & Bauer, P.J. (2005). Construction of a more coherent

story: Prior verbal recall predicts later verbal accessibility of early memories. Memory, 13, 516-532.

Hartshorn, K., & Rovee-Collier, C. (2003). Does infant memory ex

pression reflect age at encoding or age at retrieval? Developmental

Psychobiology, 42, 283-291.

Hayne, H. (2004). Infant memory development: Implications for

childhood amnesia. Developmental Review, 24, 33-73.

Hayne, H. (2006). Verbal recall of preverbal memories. In M. Garry &

H. Hayne (Eds.), Do justice and let the sky fall: Elizabeth Loftus and

her contributions to science, law, and academic freedom (79-103).

Hillsdale, NJ: Erlbaum.

Howe, M.L., Courage, M.L., & Peterson, C. (1994). How can I remember

when "I" wasn't there? Long-term retention of traumatic memories

and emergence of the cognitive self. Consciousness and Cognition,

3, 327-355.

Hunt, P., & Campbell, B.A. (1997). Developmental dissociation of the

components of conditioned fear. In M.E. Bouton & M.S. Fanselow

(Eds.), Learning, motivation and cognition: The functional be

haviorism of Robert C. Bolles (pp. 53-74). Washington, DC:

American Psychological Association.

Jacobs, W.J., & Nadel, L. (1985). Stress-induced recovery of fears and

phobias. Psychological Review, 92, 512-531.

Mineka, S., & Zinbarg, R. (2006). A contemporary learning theory

perspective on the etiology of anxiety disorders. American Psy

chologist, 61, 10-26.

Nelson, C.A. (1995). The ontogeny of human memory: A cognitive neu

roscience perspective. Developmental Psychology, 31, 723-738.

Peterson, C, & Rideout, R. (1998). Memory for medical emergencies

experienced by 1- and 2-year-olds. Developmental Psychology, 34,

1059-1072.

Pillemer, D.B., & White, S.H. (1989). Childhood events recalled by children and adults. In H.W. Reese (Ed.), Advances in child de

velopment and behavior (Vol. 21, pp. 297-340). Orlando, FL: Ac

ademic Press.

Richardson, R., & Fan, M. (2002). Behavioral expression of conditioned

fear in rats is appropriate to their age at training, not their age at

testing. Animal Learning & Behavior, 30, 394-404.

Seress, L. (2001). Morphological changes of the human hippocampal formation from midgestation to early childhood. In C.A. Nelson

& M. Luciana (Eds.), Handbook of developmental cognitive neuroscience (pp. 45-58). Cambridge, MA: MIT Press.

Simcock, G., & Hayne, H. (2002). Breaking the barrier: Children do not

translate their preverbal memories into language. Psychological

Science, 13, 225-231.

Simcock, G., & Hayne, H. (2003). Age-related changes in verbal and

nonverbal recall during early childhood. Developmental Psychol

ogy, 39, 805-814.

Yap, C.S.L., Stapinski, L., & Richardson, R. (2005). Behavioral ex

pression of learned fear: Updating of early memories. Behavioral

Neuroscience, 119, 1467-1476.

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