Development and Aging Relations Between Episodic Memory, Suggestibility, Theory of Mind, and Cognitive Inhibition in the Preschool Child

Scandinavian Journal of Psychology, 2006, 47, 485–495 DOI: 10.1111/j.1467-9450.2006.00542.x

Blackwell Publishing Ltd Development and Aging Relations between episodic memory, suggestibility, theory of mind, and cognitive inhibition in the preschool child

ANNIKA MELINDER, TOR ENDESTAD and SVEIN MAGNUSSEN University of Oslo, Norway

Melinder, A., Endestad, T. & Magnussen, S. (2006). Relations between episodic memory, suggestibility, theory of mind, and cognitive inhibition in the preschool child. Scandinavian Journal of Psychology, 47, 485–495. The development of episodic memory, its relation to theory of mind (ToM), executive functions (e.g., cognitive inhibition), and to suggestibility was studied. Children (n = 115) between 3 and 6 years of age saw two versions of a video film and were tested for their memory of critical elements of the videos. Results indicated similar developmental trends for all memory measures, ToM, and inhibition, but ToM and inhibition were not associated with any memory measures. Correlations involving source memory was found in relation to specific questions, whereas inhibition and ToM were significantly correlated to resistance to suggestions. A regression analysis showed that age was the main contributor to resistance to suggestions, to correct source monitoring, and to correct responses to specific questions. Inhibition was also a significant main predictor of resistance to suggestive questions, whereas the relative contribution of ToM was wiped out when an extended model was tested. Key words: Episodic memory, theory of mind, cognitive inhibition, suggestibility, executive functions, forensic context. Annika Melinder, Department of Psychology, University of Oslo, 0317, Oslo, Norway. E-mail: [email protected]

INTRODUCTION Niemb, 2003). We here use the term suggestibility to refer to the incorporation of incorrect post-event information into a Episodic1 memory refers to the explicit memory of an event memory report, which might result in inaccurate or even false that took place at a speciﬁc time and place in the individual’s memories of an event (Ceci & Bruck, 1995). own personal history. According to Tulving (2002), episodic Despite a general consensus regarding the relation between memory is not present before about 4 years of age, but other age, memory and suggestibility, some authors suggest that researchers believe that episodic memory is present, but less memory performance is only partly explained by age (Poole accessible for testing earlier in life (Bauer, 1996; Bauer & & Lindsay, 2001), and that children who do remember their Wewerka, 1995; Howe & Courage, 1993, 1997). Episodic memory former experiences actually make memory errors (Powell & includes an “autonoetic” kind of consciousness that allows us Roberts, 2002). Young children’s failure to resist suggestive to be aware of the subjective time when an event took place information has been related to immature internal control (Naito, 2003; Tulving, 2002). This autonoetic aspect of episodic mechanisms (Bruck, Ceci & Melnyk, 1997; Harnishfeger, 1995), memory has been related to a person’s sense of self, which and several studies have looked at the relationships between with reference to memory is termed “the cognitive self” (Howe suggestibility and executive functions such as inhibitory con- & Courage, 1993, 1997). The emergence of a cognitive self around trol (Roberts & Powell, 2005; Ruffman, Rustin, Garnham & the age of two makes possible the early organization of infor- Parkin, 2001), and theory of mind (Scullin & Bonner, 2006; mation and experiences into an episodic memory form. Although Welch-Ross, Diecidue & Miller, 1997). However, no single episodic memory allows the individual to consciously re- study has looked at executive functions and ToM in relation experience past experiences, it does not always succeed in to suggestibility and episodic memory in a wider range of tracking the memory accurately back to the situation, con- preschool aged children. In addition, most of the studies designed text, or source in which the event to be remembered took place. in context of the children-as-eye-witnesses research have tested The quantity and quality of episodic memory performances North American samples; no Scandinavian study has mapped are age dependent; young children report fewer memories than the general socio-cognitive development in relation to memory older children and adults in free and cued recall (Baker-Ward, and suggestibility. Although Anglo-Saxon cultures are quite Ornstein, Gordon, Follmer & Clubb, 1995; Bruck & Ceci, 2004; similar, there are factors that may vary between the cultures Goodman & Melinder, in press; Poole & Lindsay, 1995), and and affect the developmental trajectories of cognitive functions. their memories are more susceptible to suggestive post-event information such as misinformation, repeated questioning, and the use of props (Ackil & Zaragosa, 1995; Cassel & Bjorklund, Episodic memory development 1995; Ceci & Bruck, 1995; Priestley & Pipe, 1997; Salmon & Pipe, There are several factors that might contribute to the fragility 2000; Schacter, 2001; but see Finnilæ, Mahlberga, Santtilaa & of episodic memory and the greater suggestibility of young

© 2006 The Authors. Journal compilation © 2006 The Scandinavian Psychological Associations. Published by Blackwell Publishing Ltd., 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA. ISSN 0036-5564.

486 A. Melinder et al. Scand J Psychol 47 (2006) children, but immature source monitoring skills have been tasks (Stroop, 1935; Zelazo, Müller, Frye & Marcovitch, identified as a critical factor (Giles, Gopnik & Heyman, 2002). 2003). Cognitive inhibition is an executive process that helps Source memory, the ability to identify the origin of a memory the individual to ignore irrelevant stimuli. Because cognitive element, is one of the defining characteristics of episodic inhibition facilitates s memory retrieval by suppressing imme- memory. This ability improves between the age of 4 and diate responses long enough to search memory and provide 6 years. Experimental evidence indicates that source memory well-thought answers (Lorsbach, Katz & Cupak, 1998), it develops gradually during the preschool years, both with might be argued that stronger resistance to suggestion should respect to the ability to discriminate between external sources be observed among children with more developed cognitive of information – e.g., who said what (Lindsay, Johnson & inhibition capacities. Empirical research tends to support Kwon, 1991) – and the ability to discriminate between exter- this prediction. For example, Alexander et al. (2002) found nal and internal sources – e.g. distinguishing between what that 3- to 7-year-old children’s memory errors and suggesti- is imagined and what is said (Foly, Johnson & Raye, 1983). bility were predicted by level of cognitive inhibition, indexed In particular, if sources are similar (Lindsay et al., 1991), or by a Stroop-like task (the Day/Night task; Gerstadt, Hong if memory testing is delayed (Parker, 1995), young children & Diamond, 1994). Cognitive inhibition was inversely related tend to perform worse than older children in both non- to total incorrect units provided in free recall (r = −0.34), suggestive and suggestive paradigms. and to omission errors (r = −0.29) made to misleading yes-no Giles et al. (2002) investigated the association between questions, with age controlled. A recent study that examined suggestibility and source monitoring in 32 children (ranged 5–7-year-old children’s susceptibility to suggestibility, did not 3–5 years of age) after being presented with a story in two find any relationship between three measures of inhibition sensory modalities (e.g., in a silent video and in a spoken (including the Day/Night task) and resistance to suggestion narrative read by the experimenter) about a young boy feed- (Roberts & Powell, 2005). A fourth measure of inhibition ing his dog. Each of the six test items used to assess children’s (verbal retroactive inhibition) explained in combination with ability to resist suggestion consisted of a declarative phase age 17% of the variance in suggestibility scores. A limitation (always including incorrect event information), followed by of the study, pointed out by the authors, was that the sample a question that prompted for agreement with what was said. had an average age of close to six years, an age at which If the child yielded to the question, he/she made a false children evince ceiling effects on some of the tasks (e.g., the alarm, if however he/she rejected the question, resistance to Day/Night task). In the present study we include a wider suggestion was evinced. The source monitoring measures age-range of children. consisted of two separate tasks that assessed children’s abil- Cognitive inhibition has been related to the ability to ities to identify specific story details. Specifically, they found avoid false alarms and to source monitoring in 6-, 8-, and a positive correlation between source-monitoring and the 10-year-old children after watching a video and/or listening ability to resist suggestion, also when age was partialled out. to a tape about a dog (Ruffman et al., 2001). It is frequently Giles and coworkers also showed that preschool children claimed that if source information is presented without false were more able to resist post-event information when they induction, multiple exposures to an event (e.g., both watch- had been encouraged compared to when they had not been ing and listening to the tape) should strengthen the memory encouraged to think about the source of their knowledge. (Pezdek & Roe, 1995; Quas, Schaaf, Alexander & Goodman, Although the authors conclude that “preschool aged children’s 2000). Ruffman et al. argued that a single presentation of the suggestibility is reduced when they are attuned to the epistemic event (e.g., watching or listening to a tape) would provide origins of mental representation” (Giles et al., 2002, p. 291), familiarity cues, but additional episodic strategic information other factors might have contributed to the result. Source would be needed to accurately identify the item’s source. Thus, memory does not operate in isolation, but is closely linked successful source monitoring would require that participants to executive functions such as to cognitive inhibition, i.e. the showed extra strong inhibitory control of automatic familiarity- ability to inhibit automatic responses in order to perform based retrieval processes that only were presented once. goal-directed tasks (Ruffman et al., 2001), and to ToM because Based on previous research and theoretical considerations, ToM emphasizes the representational nature of the mind we predicted that children’s resistance to suggestion (e.g., to (DeLoache & Marzolf, 1995; Welch-Ross et al., 1997). produce false alarms) would be related to inhibition (Roberts & Powell, 2005; Ruffman et al., 2001). Because source monitoring depends strongly on self-reflective processes, which Individual differences might be helped by stronger inhibitory activity (Johnson et al., Cognitive inhibition. Source monitoring functions rely on 1993), inhibition would also be related to source memory. strategic, self-reflective, and inhibitory control processes (Johnson, Hashtroudi & Lindsay, 1993; Ruffman et al., Theory of mind (ToM). The capacity to understand contra- 2001). Cognitive inhibition refers to mental processes that dictory statements and representations – the theory of mind relate to control and inhibition of action sequences (Perner (Astington, 1993; Flavell, 1985; Perner & Davies, 1991) – & Lang, 2000) and is usually tested in Stroop-like card sorting helps children to separate their thought about a construct or

Scand J Psychol 47 (2006) Episodic memory 487 another person’s mind from their own. Some talk about “the a task to the youngest children that aimed to measure more four year shift”, referring to the stage when normal children rudimentary forms of a false belief (Wimmer & Perner, 1983), reach a level of competence in detecting false beliefs, or before the false task commonly used in the literature to index display stable ToM (Perner & Lang, 2000), and this ability ToM was provided (Gopnik & Astington, 1988; Sabbagh, emerges almost in parallel with performance on executive Xu, Carlson, Moses & Lee, 2006). tasks (Hughes & Russell, 1993). Autistic children, known to The fact that an advanced ToM is associated with resistance have ToM deficits, are likewise impaired on executive func- to suggestive influences (Bruck & Melnyk, 2004), that executive tions (Ozonoff, Pennington & Rogers, 1991; Rönnberg & functions emerge in parallel with ToM scores (Hughes & Melinder, in press), a finding that supports the assumption Russell, 1993), that increased inhibition and decreased sug- of such a link between ToM and executive functions, such as gestibility are correlated (Roberts & Powell, 2005), and that inhibition. There are two competing explanations of the rela- source monitoring is related to suggestibility (Giles et al., tion between inhibition and ToM (Moses, 2001). According to 2002), indicate that executive functions and ToM form a set the expression view, children’s failure to solve a false-belief of cognitive processes that are essential to report correctly task occurs because of the executive demands that these tasks information regarding a target event and its source. Further- pose, not because the children lack an understanding of more, interactions between the various cognitive skills may false-beliefs (Perner, Lang & Kloo, 2002). When the execu- produce effects on suggestibility. For example, Roberts and tive functions develop to assist in solving the false-belief tasks, Powell (2005) discuss whether children with a mature theory children are able to express their latent ToM understanding. of mind, but who lack inhibition skills would be more at risk According to the emergence view, executive functions are than children with less inhibitory control, to succumb to necessary for the emergence of ToM abilities because general suggestive information in a forensic type interview. In the executive functions enable children to take advantage of present study we test this idea. specific experiential everyday experiences (e.g., number of From a different point of view, it might be argued that in siblings, exposure to opportunities to reflect on the discrepancy order to detect deceptive tasks, including those in which the between reality and mental states; Brown, Donelan-McCall child is expected to detect demand characteristics, inhibition & Dunn, 1996) necessary to ToM development. skills are needed to decide on the answer and to control any The ability to understand that an interviewer entertains impulse to yield to pressure (Lorsbach et al., 1998). a false belief has a link to suggestibility. A mature ToM has In line with the arguments outlined above, we predicted been associated with stronger resistance to suggestibility, that children with stronger cognitive inhibition and more when age is controlled for (Bruck & Melnyk, 2004). For example, developed theory of mind capability would be least susceptible Welch-Ross et al. (1997) showed that ToM predicted 3–5- to suggestive influences. However, because we assume that year-old children’s suggestibility, in the sense that children ToM is supported by cognitive inhibition, we expected that who performed better on a task that indexed the understanding stronger resistance to suggestive questioning would be of conflicting mental representations, accepted less misinfor- predicted by cognitive inhibition, operating in combination mation. In a subsequent study, Welch-Ross (1999) demon- with age. Thus, when inhibition and ToM is entered into the strated that when children passed a standard theory of mind model ToM would contribute less or not at all. task, they were less likely to incorporate misinformation, but The principal aim of the present study was to map the only those who had poorer story memory. Other studies relationships between the development of episodic memory, have failed to find a relationship between theory of mind the executive function of cognitive inhibition, theory of mind, and suggestibility (Quas & Schaaf, 2002). There are also and suggestibility, during preschool. Children between 3 and indications that when younger children (e.g., 48 months) 6 years of age saw two slightly different versions of a video receive negative feedback, they change the answers as frequently film each containing 16 events; eight of which varied between as do older children (e.g., 60 months) (Scullin, Kanaya & Ceci, the videos. The children were later tested for their memory 2002). Melinder, Scullin, Gunnerød and Nyborg (2005) failed of the videos, and for the ability to decide in which version to observe a positive correlation between shift scores on a the various elements were shown, using free recall, specific standardized measure of suggestibility (the Book Suggesti- questions, suggestive yes/no questions, and source questions. bility Scale for Children, BSSC; Warren, Scullin & Ceci, 1999) Before doing the memory test, the children completed two and age. There is an ongoing debate whether the different false ToM tasks and one cognitive inhibition task. belief tasks measure the same cognitive abilities (Wellman, Cross & Watson, 2001) or capture different aspects of episodic memory (Holmes, Black & Miller, 1996; Naito, 2003). METHOD Inconsistencies among studies might be explained by the demand to the autonoetic consciousness level involved in the Participants tasks that have been used. According to the expression view, A total of 115 children were recruited through day care centers after it is important to age-adjust the test items to measure ToM the parents had consented to participation. The sample included (Wellman & Liu, 2004). In the present study we administered 23 three-year-olds (48% female, M = 41.26, SD = 3.16) 36 four-year-

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Theory of mind. In order to map different expressions of theory of mind capabilities progressively, as suggested by Wellman and Liu (2004), and to be able to capture multiple cognitive ToM abilities (Holmes et al., 1996), we employed two sets of the main task, each including two subordinate tasks. The first task in the first set was developed for the study and administered to the group of 3-year-old children. The purpose was to see if the child understood the connection between perception and knowledge in the other person’s mind. A trained research assistant (RA) presented a wooden block and a paper sheet that was folded with the corner towards the RA. The RA then asked the child if he/she could put the block out of sight from the RA. The RA turned around, and the child was supposed to hide the block for the RA. If the child succeeded with this task, the RA proceeded to the next task, and the child was credited with two points. If, however, the child was unable to understand the first task, the RA continued to explain by taking the block in her hand and said: “Well, now it is my turn to put the block somewhere on the table. But I need your help. I put the block somewhere and I lean back. Then, you will have to tell me if I can see the block or not. OK. Let’s try.” The RA placed the block on the table three times (one time under the table, one time behind the paper sheet so that only the child could see it, and the last time behind the paper sheet so that only the RA could see it) and the child was supposed to tell whether the RA could see the block or not. If the child succeeded, they were given one point. In the second ToM task (e.g., a content false-belief task), the Fig. 1. The two set of pictures used in the inhibition task, the “Day children were shown a familiar candy box (“Smarties”) that had and Night”. Left panel depicting the control condition (1a, 1b) for unfamiliar content (Gopnik & Astington, 1988) and were first asked assessing the child’s understanding of the rules before one intro- what they thought was inside the box. All answers with a reference duces the experimental condition, and right panel depicts card used to candy were considered correct. The RA then opened the box and in the experimental condition. showed the content to the child, saying: “You said it was candy inside the box, but look here, the box is filled with crayons. When you have left this room, another child will enter. What do you think that child will believe is in this box?” The answer was judged as correct, if the child’s answer was referring to candy. olds (44% female, M = 54.72, SD = 3.75), 31 five-year-olds (55% The other set consisted of the “Smarties” task described above and female, M = 65.16, SD = 1.92) and 25 six year-olds (56% female, a second “Milk-box” task similar to the location false-belief introduced M = 74.96, SD = 3.03) All children were native Norwegian speakers by Wimmer and Perner (1983). In the milk box task, which was and lived in Oslo. developed for the present purpose and administered to the 4-, 5- and 6-year-old children, the RA placed an empty milk box and a wallet on the table in front of the child and said: “Look, here is a milk box Materials and a wallet. There are some coins in this wallet. But now, I do something strange. I put the coins into this milk box” – the RA put The stimulus material. Video recordings were made by a digital the coins into the empty milk box and continued: “When you have Sony, DCR-PC2E camera; the tapes were edited and transferred to left this room, another child will come here. Where do you think DVD format, and viewed on 17″ sized computer screens. Each video that child will look for the coins?” Answers that referred to “in the contained 16 identifiable events, eight of which were common to the wallet” were scored as correct. The second ToM task for the 4-, 5-, and two versions and eight of which varied between the versions (see the 6-year-old children were identical to the “Smarties” described above. Appendix for a description of the content of the video sequences). Each child was thus introduced to two tasks; scores for each task The child actors were a 6-year-old girl, a 9-year-old boy, and a 10- ranged from 0 to 2, giving a range on the total scores for ToM from year-old girl. 0 to 4.

Cognitive inhibition. We employed the Day and Night task (Gerstadt Memory questionnaire. The structured interview started with a set et al., 1994; Fig. 1) to measure cognitive inhibition, including the of free recall questions including eight prompts, such as: “Tell me control cards (Fig. 1a,b) to assess the child’s understanding of the everything that you remember from the videos you just saw”. The rules before administering the test card. The control card condition interviewer then went on to ask nine specific questions that directed requested the child to answer “sun” when shown the wave-formed the child to a particular event and required a brief narrative response card, presumably requiring no control of response impulse. The (e.g., “What kinds of fruit did the children eat?”), and these ques- experimental condition requested the child to answer “night” when tions were followed by 15 yes/no questions, ten of which contained shown the sun card, presumably requiring a control of the impulse suggestive, misleading information (e.g., “Did the children take off to say “day”. Sixteen trials were administrated for both control and their clothes when playing?”), and five yes/no (e.g., non-misleading) experimental condition, eight with each card in a random order. questions based on correct information (e.g., “Did a man enter?”). The scores ranged from 0 to 16 points each, with higher scores Finally, 10 source questions were asked. These included only correct indicating greater understanding of the rules and greater inhibitory event information, such as: “In which video did the boy take a toy control. Performance on this task is significantly related to other from the girl? Was it in the first video, when you sat there [RA measures of cognitive inhibition (Carlson & Moses, 2001). points], or in the last one when you sat there [RA points]?”

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Procedure RESULTS Our goal with the present study was to first clarify the The children were tested individually in a separate room in her/ nature of the developmental relationship between episodic his day care center, by two research assistants (RA). First, one of memory and individual differences in executive functions the RAs presented to the child with two slightly different versions of a 2 × 7 min. video film. The children were provided with an and ToM in relation to suggestibility by providing a compre- additional physical encoding marker by switching chairs and hensive model for this interplay in relation to interviewer positions when watching the two video versions. The purpose of induced suggestibility. An implicit aim was further to deter- this manipulation was to make the sources more salient. After mine whether there were any executive and ToM functions watching the videos, the child was given the cognitive inhibition and that reliably could be measured prior to the test situation ToM tasks. Finally, the other RA entered the room and interviewed the child according to the experimental protocol. The session lasted that would predict memory outcome and susceptibility to for about 50 minutes. suggestion. Based on previous research we presumed ToM to be dependent on inhibition and predicted that in addition to age, inhibition would explain a large part of the variance Coding in suggestibility scores. Interviews were transcribed and coded for units of information in Preliminary analyses revealed no main or interaction relation to free recall questions and for accurate answers to specific, effects with gender as a factor. The results for boys and girls suggestible, and to source questions. The narrative information pro- were therefore collapsed in the subsequent analyses. Unless vided by children in response to the free recall questions was scored for units of information, using a system similar to those employed otherwise specified, the level of significance was set to in earlier studies of children’s event recall (e.g., Alexander et al., p < 0.05. 2002; Quas & Schaaf, 2002). Statements about agents, objects, actions, or descriptors that included information about the event were scored as correct or incorrect. If, for example, the child Descriptive statistics recalled: “They played with a green ball . . . and dad called them for dinner”, they were credited with seven units of information: five Table 1 summarizes the descriptive statistics, including range correct units for “they”, “played with”, “dad”, “called for”, and of scores on dependent variables. Memory scores included “dinner”, and two incorrect units of information for “green” and total units of information and the frequency of correct infor- “ball” (because the videos did show children playing with a green mation in free recall, number of correct answers to the spe- ball). We collapsed data across the free recall questions and cific questions, number of false alarms to suggestive yes/no responses were scored as correct if it occurred in either video (total correct free recall). Redundant information was only scored once. misleading questions, number of hits on yes/no leading ques- Answers that did not relate to the videos or personal digressions tions, and the number of correct responses to source ques- were not scored. Total units of information and total correct units tions. When evaluating cognitive inhibition scores, we first of information were summed within each interview. computed the children’s average performance in the control The nine specific questions were based on correct event infor- condition which was significantly better, M = 14.10, SD = mation, and the child was given one point for correctly recalling the target event. If, for example, the child answered “a pear” in 3.72, than the performance in the experimental condition, response to the question: “What kind of fruit did the children M = 12.54, SD = 5.07, t(114) = 3.56 (paired sample); almost eat?” one point for a correct answer was scored. In five of the all children understood the instructions, but a significant questions, the child could give two correct answers because of proportion of them lacked the ability to restrain the primed the two versions of the videos, however only one was considered a (incorrect) response. credit. On the yes/no suggestive questions, children received a hit score if they answered the question correctly (e.g., responding “yes” to Table 1. Descriptive statistics of the variables (n = 115) questions based on correct event information). If, however, the child said “yes” to questions based on incorrect event information (e.g., Variable MSDMin Max a misleading question), they received a false alarm score. This summed up to a maximum of 10 points for incorrectly assenting to Age in months 59.24 12.02 37 80 the interviewer’s misleading questions (e.g., false alarms) and five Free recall points for correct recognition in yes/no questioning (or to non- Total free recall 17.34 20.61 0 127 misleading questions). The scoring of false alarms followed Giles Correct free recall 16.25 20.03 0 127 et al.’s (2002) scoring procedure. Finally, the 10 source monitoring Specific questions questions were scored with credits given to telling which film contained Correct answers 5.65 2.53 0 9 a particular scene. Suggestible y/n (misleading) questions Two RAs independently scored 20% of the protocols for each of False alarms 2.86 3.00 0 10 the age group, giving 588 child free recall answers. Percentage agree- Suggestible y/n (non-leading) questions ment was 97% for the free recall and correct free recall questions. Hits 3.90 1.11 0 5 The remaining interviews were scored by a single RA. For the spe- Source questions cific questions, suggestive yes/no questions, and source monitoring Correct answers 6.08 2.48 0 10 questions, reliability tests were not conducted because scoring was Executive functioning obvious. An exception is the questions with two correct responses. Theory of mind 2.57 1.67 0 4 These questions were strictly scored according to the scoring rule by Cognitive inhibition 12.54 5.07 0 16 one of the RAs and then double checked by the first author.

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Fig. 3. The transformed Z-scores as a function of age, for each of Fig. 2. The development of memory performance converted to Z- the theory of mind and cognitive inhibition. scores as a function of age, for four measures of memory, as labeled in the ﬁgure: Direct questions, suggestive questions, source questions and free recall.

On the ToM tasks, 52% of the 3-year-olds, 30% of the Figure 3 shows the development of scores on the cognitive 4-year-olds, 10% of the 5-year-olds, and 4% of the 6-year-old inhibition and ToM tasks, likewise converted to Z-scores. children failed to pass at least one of the tasks. Table 2 ANOVAs showed a significant effect of age on cognitive shows the distribution of children’s responses to the ToM inhibition, F(3, 111) = 18.83, η2 = 0.34, and ToM skills, tasks. The correlations between scores on the two ToM tasks F(3, 111) = 16.51, η2 = 0.31. Thus, development of the ToM were moderate to high: milk box and Smarties, r = 0.50, and the cognitive inhibition scores are parallel and closely p < 0.01, milk box and total score, r = 0.85, p < 0.01, Smarties similar to the development of memory. and total score, r = 0.85, p < 0.01, wooden block and Smarties, r = 0.72, p < 0.01, and finally wooden block and total score, r = 0.83, p < 0.01 (all 2-tailed). Relationships between episodic memory, executive functions, ToM, and suggestibility To explore the relations between episodic memory, executive Development of episodic memory and executive functions functions, ToM, and suggestibility, we computed correla- Figure 2 plots the developmental trajectories of the episodic tions between the scores. Because age affected all measures, memory measures and the resistance to suggestive question- this factor was controlled for in these analyses. As Table 2 ing, with data converted to Z-scores for easy comparison. shows, correct answers to specific questions were significantly There is an almost linear relationship between chronological related to both source memory and to production of units age and scores on the various memory measures;2 note that of information, not very surprising perhaps, since they in case of the suggestibility measure the rate of false alarms were all prompted with correct event information, or free is depicted as a descending trend. A series of ANOVAs recall questions. Also expected are the negative correlations confirmed that age affected the total amount of free recall between false alarms and both ToM and inhibition, support- responses, F(3, 111) = 22.59, η2 = 0.38, and the free recall ing our expectations and fit into a wealth of evidence for correct responses, F(3, 111) = 24.57, η2 = 0.40. Not surpris- these associations. Contrary to prediction, inhibition did not ingly, the older children produced more than the younger correlate with source memory, suggesting that at least this children in free recall and when we compared the total type of inhibition is not involved in searching the memory amount of free recall units with the correct amount of free for correct source. ToM and inhibition correlated positively, recall, the content of the children’s memory was mostly as expected. correct for all age groups, r = 0.99, p < 0.01, n = 115. Similar We further partialled out all correlations with units of results were observed for the number of correct responses, information and age to evaluate whether production of both with respect to the specific questions, F(3, 111) = 29.82, verbal material would have an impact on the results. Except η2 = 0.47, source questions, F(3, 111) = 8.10, η2 = 0.18, and that the significant correlation between units of information resistance to suggestive questions, F(3, 111) = 26.49, η2 = and specific questions held up, and was replaced with a 0.42. Thus, the older the children, the more superior were significant negative correlation between units of information they in all aspects of memory performance, and the develop- and production of false alarms (r = −0.24, p = −0.01), the mental trends of the various measures are closely similar. trend was the same as when age alone was controlled.

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Table 2. Distribution of children’s responses to the theory of mind regression analysis. The model was significantly different from tasks (n = 115) zero, R = 0.70, F(3, 111) = 36.42, p < 0.01, and accounted for 50% of the variance in false alarm scores. Further, the Wooden box Milk box Candy model involved two main effects of age (β = −0.33, t = −3.65, 3-year-old 4, 5, and All age β − − only 6-year-old groups p < 0.01) and cognitive inhibition ( = 0.35, t = 4.17, p < 0.01) respectively, which implied that both weak cognitive Correct 16 (62) 65 (73) 70 (61) inhibition and young age contributed significantly to a high Incorrect 10 (38) 23 (26) 33 (29) rate of false alarms. In this model ToM scores (β = −0.15, Don’t know 0 1 (1) 12 (10) t = −1.70, p = 0.09) did not significantly predict susceptibility Number of participants 26 89 115 to suggestions. A regression analysis was carried out to Notes: Number of participants differs due to the different evaluate whether the model with age and ToM alone accounted experimental conditions that were offered according to participant’s for variance when inhibition was omitted. This model was age. All of the 26 three-year-old children received the Wooden box also significant, R = 0.66, F(2, 112) = 40.05, p < 0.01, but task, whereas none of the three-year-old children received the Milk accounted for less variance in false alarm scores (e.g., 42%). box task. All children received the Candy task. Numbers in parentheses indicate percentage of each task’s response rate. Additionally, standardized coefficients from this model (β = −23, t = −2.63, p = 0.01), were lower than for the full model, suggesting a better fit with the model including inhibition. We reasoned that executive functions would predict children’s Using the same predictors as in the first regression model accuracy in response to suggestive and source questions, so onto correct responses to specific questions, this second model that children with good inhibitory control would be resistant was also significantly different from zero, R = 0.69, F(3, 111) to suggestible questions and perform better on the source = 33.04, p < 0.01, and accounted for 47% of the variance. monitoring test compared with children with less inhibitory As expected from the correlation analyses, only age (β = 0.60, control. Two groups were formed by median split (Md = 15) t = 6.46, p < 0.01) was a significant predictor; cognitive one group composed of the children scoring 1–15 points inhibition (β = 0.04, t = 0.47, p = 0.64) and ToM scores (51.3% of the sample), and a second group composed of the (β = 0.10, t = 1.12, p = 0.27) were not. children scoring 16 points (maximum score) on the inhibition We finally regressed correct responses to source questions. task. Results indicated that the high scoring group (M = 1.36, Again the model differed significantly from zero, R = 0.46, SD = 1.67) significantly outperformed the low scoring group F(3, 111) = 9.84, p < 0.01, and again age was the only signi- (M = 4.29, SD = 3.30) in resistance to false alarms, F(1, 113) ficant predictor for correct source memory (β = 0.32, t = = 35.62, p < 0.01, η2 = 0.24. For the source monitoring, 2.85, p < 0.01), but cognitive inhibition (β = 0.08, t = 0.80, children in the high group (M = 6.55, SD = 2.61) evinced more p = 0.42) and ToM scores (β = 0.12, t = 1.10, p = 0.28) were correct answers than did children in the low group (M = 5.63, not, as expected from the correlation analyses. No interac- SD = 2.28), F(1, 113) = 4.12, p < 0.05, η2 = 0.04, suggesting tions or curvilinear trends were found for any of the models. that inhibition affected source monitoring significantly. In summary, age is the strongest predictor of both responses We also hypothesized that better theory of mind skills to specific questions and of source memory performance, would contribute to lower suggestibility through the relation while cognitive inhibition is an additional, independent pre- between theory of mind and inhibition. To detect the relative dictor of resistance to suggestive questions. Theory of mind’s contribution of age, inhibition and ToM on susceptibility to position in regard to suggestibility held up in the model suggestions (e.g., false alarms), we carried out a multivariate when inhibition was included.

Table 3. Correlation between the memory measures, theory of mind, cognitive inhibition, and suggestibility when age was partialled out (df = 112)

Speciﬁc Suggestible Source Free recall questions questions questions ToM questions

Suggestible questions −0.13 Source questions 0.25** 0.11 ToM 0.12 −0.24** 0.12 Free recall 0.24** −0.07 0.07 0.01 Inhibition 0.07 −0.41** 0.10 0.24** −0.08

Notes: Free recall questions equals total correct number of such questions (correlation with all free recall = 0.98). * Correlations are signiﬁcant at the p < 0.05 level (2-tailed). ** Correlations are signiﬁcant at the p < 0.01 level (2-tailed). For all but the suggestible questions, for which the rate of false alarm is marked, correct answers are given.

DISCUSSION marked improvement in executive functions and in theory of mind abilities (Kloo & Perner, 2003; Perner & Lang, 2000). Several studies have been carried out, especially in North Recent findings show that children from Canada, India, America, with the aim to investigate the cause of children’s Peru, Samoa, and Thailand show a cross-cultural synchrony susceptibility to suggestion and memory abilities. To the in the onset of ToM reasoning between the ages of 3 and 5, authors’ knowledge no study have included measures of both with a small proportion of 3-year-olds (14%), modest inhibition and ToM in their designs. Further, we sampled proportion of 4-year-olds (46%), and a large proportion data from a wider age-range of Scandinavian preschool of 5-year-olds (85%) passing a false-belief task (Callaghan, children on the developmental relationship between episodic Rochat, Lillard et al., 2005). The present study indicates a memory, individual differences in executive functions, ToM, somewhat earlier start among Norwegian children with 48% and suggestibility because cultural differences may play an of the 3-year-olds, 70% of the 4-year-olds and 90% of 5-year- important role for resistance to suggestions. The present study old children providing a correct response to the ToM task. suggests three main conclusions that correspond to our research The emergence of ToM is not instantaneous or abrupt but questions and refer to three logical levels of analyses: a gradual and the duration of the process may differ across descriptive, correlation and a predictive level. We discuss both cultures and individuals. Cultural differences in the each of them below, and comment on the study’s limitation way people attribute human actions (e.g., to contextual before we point to future directions for research in this area. versus internal causes), might influence the progression of ToM abilities (Lillard, 1998). A potential limitation in the present study is that one of Developmental trajectories in episodic memory and executive the tasks used to measure ToM in the 3-year-old children functions, and ToM differed from the task presented to the other age groups, and The results of the present study demonstrate a steady develop- the results may be biased in favor of the younger children. ment of episodic memory during the preschool age of 3 to However, the correlation between ToM tasks was positive 6 years, confirming the results of a large number of studies and they correlated with the task of cognitive inhibition, a (see reviews by Conway & Rubin, 1993; Goodman & Melinder, pattern of results found in similar studies on Western in press; Nelson & Fivush, 2004; Reese, 2002). The results (Carlson & Moses, 2001; Perner et al., 2002) and Chinese demonstrate similar development trends for the quantity of preschoolers (Sabbagh et al., 2006). information in free recall, the magnitude of correct infor- We further reasoned that children with stronger inhibitory mation in response to specific and suggestive questions, and capabilities would be better to ignore task-irrelevant infor- in source memory. As children grow older, the length, richness, mation, and as such be more focused on target event infor- and complexity of the recall memories increase (Pipe, Lamb, mation. This ability would assist the identification of the Orbach & Esplin, 2004). We also confirm the general finding source of an event, and the rejection of non-target suggestive that children’s accounts of experienced neutral events in free information. However, no such association was observed, recall are quite accurate (Oates & Shrimpton, 1991; Pipe et al., but this might partly be due to the fact that about half of 2004; but see Poole & Lindsay, 2001). the children evinced ceiling effects on the Day/Night task. When age was partialled out the correlations between the In the study of Gerstadt et al. (1994), 5-year-old children various memory measures were moderate. Strongest associ- produced around 80% correct on the task comparable to the ations were observed between accurate responses to specific present results. Interestingly, those children who obtained and source questions, both of which were prompted by correct maximum scores on the inhibition task significantly out- event information. Accurate responses to specific questions performed the low-performance group on source memory were related to number of units of information, indicating accuracy, consistent with previous findings that source that length of verbal production played a role when children monitoring depends on self-reflective processes, assisted by were requested to elaborate on a cued recall question. This inhibitory activity (Johnson et al., 1993). correlation disappeared, and was replaced by a relatively The present results add to the robust body of cross- weak negative correlation between free recall responses and cultural findings that cognitive inhibition is linked to the production of false alarms when age and units of information development of theory of mind. A very recent report were controlled for. This result indicates that interviewers supports the emergency view (Sabbagh et al., 2006), demon- may safely prolong the free recall section of an interview by strating that attaining a certain level of executive functioning using a variety of open-ended prompts rather than specific does not by itself yield better ToM abilities. In other words; questions to elicit information from the children without the relation between executive functions and ToM abilities an increase the false alarm rate (Melinder, 2004; Poole & should not be attributed to the executive demands posed by Lindsay, 2001). the ToM tasks. The children in our sample evinced as good Next, we examined developmental trends in cognitive inhibitory control scores as the American sample, but their inhibition and ToM. It is commonly assumed that around ToM abilities emerged earlier than found in both American the age when episodic memory takes off children evince a and Chinese samples. In light of this finding, it would be

© 2006 The Authors. Journal compilation © 2006 The Scandinavian Psychological Associations. Scand J Psychol 47 (2006) Episodic memory 493 interesting to replicate the present study with the ToM tion to the dyadic interaction made by the individual child, arsenal used by Sabbagh et al. (2006). which predicts even experienced interviewers’ question Executive functions paralleled episodic memory develop- posing. The present paper contributes to this discussion by ment, but they were not associated with any of the memory showing that an important aspect of resistance to suggestion measures, which may indicate that there is a domain-general is the ability to inhibit automatic responses. Because ToM maturity process in the brain that impacts episodic memory did not predict suggestibility or any type of memory when development and the highly specialized executive functions age and inhibition was co-considered and previous research independently. Episodic memory includes an autonoetic has shown that results regarding ToM and suggestibility aspect (Naito, 2003) related to human’s sense of self with an are inconclusive, less attention could be given to ToM in an emergence around the period when the child becomes occu- eye-witness perspective. In the future researchers need to pied with the own mirror-picture in the second year of life continuously add measures of individual differences in their (Howe & Courage, 1993, 1997). Perhaps this is a domain- study of suggestibility, and inhibition has been verified as general aspect necessary, albeit not sufficient, for the emer- being a potent construct to include therein. gency of ToM abilities, that shares the same platform as rudimentary forms of episodic memory (e.g., the capacity to We want to thank the children who participated in the study, three organize information into episodic format). In our study we child actors who joyfully improvised real and imagery play, and found evidence for ToM abilities in half of the 3-year-old finally Gunhild Melinder for all support and love. children. This might be an indication of cultural important differences in socio-cognitive functions that need to be NOTES further examined in future research. 1 For the purpose of this paper, episodic and autobiographic memory is used interchangeably. 2 The probability of getting the observed results by chance was

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Social Development, 11, The first scene shows children playing peacefully in a sand 124–142. box (common event 1). In version A the boy takes a toy Roberts, K. P. & Powell, M. B. (2005). The relation between from the girl (A1), who starts to cry, upon which a fairy inhibitory control and children’s eyewitness memory. Applied enters and comforts her (A2). In version B the boy gives the Cognitive Psychology, 19, 1003–1018. Ruffman, T., Rustin, C., Garnham, W. & Parkin, A. J. (2001). girl a toy (B1), who in return gives him a hug. The fairy Source monitoring and false memories in children: Relation to enters and credits the boy for nice behavior (B2). The chil- certainty and executive functioning. Journal of Experimental dren then find a basket of fruit (common 2). In version A Child Psychology, 80, 95–111. they cut a pear with a knife (A3), and in B they cut a kiwi Rönnberg, J. & Melinder, A. (in press). Compensatory changes in (B3). In both versions, the girl holds the knife, and the fairy everyday memory and communication: Disabilities, abilities, and social context. In T. Helstrup and S. Magnussen (Eds.), re-enters to demonstrate the safest way to hold a knife (com- Everyday memory. London: Psychological Press. mon 3). The girl follows the fairy’s instructions and the fairy Sabbagh, M. A., Xu, F., Carlson, S. M., Moses, L. J. & Lee, K. leaves. After the fruit is eaten, they start cleaning up (com- (2006). The development of executive functioning and theory of mon 4), but then the boy stumbles and hurts his leg (com- mind. Psychological Science, 17, 74–81. mon 5). The fairy enters a third time and uses a magical Salmon, K. & Pipe, M-E. (2000). Recalling an event one year later: The impact of props, drawing and a prior interview. Applied stick to heal the boy (common 6). He is impressed and says: Cognitive Psychology, 14, 99–120. “You are a real fairy!” And the fairy replies: “Yes, I am. I Schacter, D. L. (2001). The seven sins of memory: How the mind have some gifts for you. Sit down and I will get them”. In A forgets and remembers. Boston, MA: Houghton Mifflin Co. the fairy gives glossy pictures to the girl, and a soccer ball to Scullin, M. H. & Bonner, K. A. (2006). Theory of mind, inhibitory the boy (A4). In B the girl receives a doll, and the boy a red control, and preschool-age children’s suggestibility in different interviewing contexts. Journal of Experimental Child Psychology, hat (B4). In A the fairy leaves and wishes the children fun 93, 120–138. (A5), in B the fairy leaves also but tells them to pay attention Scullin, M. H., Kanaya, T. & Ceci, S. J. (2002). Measurement of to the gifts (B5), because something special might happen. individual differences in children’s suggestibility across situations. The children then discuss what to do next, and the girl Journal of Experimental Psychology: Applied, 8, 233–246. comes up with a “Hide-and-seek” game (common 7). At Stroop, J. R. (1935). Studies of interference in several verbal reactions. Psychological Monographs, 50, 38–48. that point someone is knocking at the door, and the children Thoresen, C., Lønnum, K., Melinder, A., Stridbeck, U. & Magnussen, get scared. They take each other’s hands and say in unison, S. (in press). Theory and practice in interviewing young children: “Come in!” In A, a man, apparently confused and in a A study of Norwegian police interviews 1985–2002. Psychology, hurry, enters and exclaims: “No, it was not here, sorry to Crime & Law. bother you!” He leaves and slams the door (A6). In B a Tulving, E. (2002). Episodic memory: From mind to brain. Annual Review Psychology, 53, 1–25. woman enters, doing the same as the man (B6). The children Warren, H. K., Scullin, M. H. & Ceci, S. J. (1999). Development of look at each other and laugh. The boy re-initiates the hide- suggestibility scales for young children: A validation study of and-seek play, counts to ten, and the girl hides below a cross-situational suggestibility. Unpublished manuscript. cabinet in A (A7) and under a table in B (B7). Finally, either Welch-Ross, M. K., Diecidue, K. & Miller, S. A. (1997). Young female (A8) or a male (B8) voice tell the children to come home children’s understanding of conflicting mental representation predicts suggestibility. Developmental Psychology, 33, 43–53. for dinner, and the film ends with the children replying: “We Welch-Ross, M. K. (1999). Interviewer knowledge and preschoolers’ play just a little bit more, then we come, OK?” (common 8).