European Journal of Psychology of Education 2002, Vol. XVII, nº 3, 275-291 © 2002, I.S.P.A. Strategic competence: Applying Siegler’s theoretical and methodological framework to the domain of simple addition Joke Torbeyns Lieven Verschaffel Pol Ghesquière Katholieke Universiteit Leuven, Belgium In this study we investigated the variability, frequency, efficiency, and adaptiveness of young children’s strategy use in the domain of simple addition by means of the choice/no-choice method. Seventyseven beginning second-graders, divided in 3 groups according to general mathematical ability, solved a series of 25 simple additions in 3 different conditions. In the first condition, children could choose whatever strategy they wanted to solve each problem. In the second and third condition, the same children had to solve all problems with one particular strategy, respectively adding up to 10 and retrieval. The results demonstrate that second-graders as a whole choose adaptively between retrieval, decomposition, and counting strategies when solving simple additions, and that they use these strategies neither equally frequently nor equally efficiently. Furthermore, our results indicate that children with different mathematical ability use generally the same strategies to solve these problems, but differ in the frequency, accuracy and adaptiveness with which they apply these strategies. Finally, this study documents the value of the choice/no-choice method to assess the adaptiveness of young children’s strategy use in the domain of early arithmetic. Strategy choice and development: Siegler’s theoretical and methodological framework Recent studies on strategy use in cognitive tasks (for an overview, see Siegler, 1996) have shown that children as well as adolescents and adults have a rich variability of strategies to their disposal to solve a particular task. Siegler and Jenkins (1989) distinguish two types of strategies to solve cognitive tasks: “back-up” strategies and “retrieval”. Back-up strategies can be defined as rather time-consuming, procedural strategies. The speed of execution of a back-up The authors would like to thank Wim Van den Noortgate for his methodological assistance in the data analysis. 276 J. TORBEYNS, L. VERSCHAFFEL, & P. GHESQUIÈRE strategy is strongly influenced by problem-specific characteristics (e.g., it takes more time to count the answer to 8+3 “1, 2, 3, 4, 5, 6, 7, 8… 9, 10, 11” than to solve 2+3 with the same strategy “1, 2… 3, 4, 5”). Retrieval refers to the (quasi-)automatic activation of the answer to the problem in long term memory (e.g., “8+3=11, I know this by heart”). In principle, retrieval is executed faster than back-up strategies; moreover, the speed of execution of the former strategy is much less influenced by problem-specific characteristics than the speed of execution of the latter strategies. In their “model of strategic change”, Lemaire and Siegler (1995) distinguish four dimensions to describe developmental changes in strategy use. The first dimension (i.e., strategy repertoire) involves the different strategies that are used to solve a task. The second dimension (i.e., strategy distribution) refers to the relative frequency with which each strategy is used. The third dimension (i.e., strategy efficiency) concerns the accuracy and the speed of strategy execution. The fourth dimension (i.e., strategy selection) refers to the adaptiveness of strategy choices: Does the individual choose the cognitively most efficient strategy, i.e. the strategy that leads the individual fastest to an accurate answer to the problem? Changes in strategy use can thus occur in at least four different ways: The acquisition of new strategies and the abandonment of old ones (dimension 1), changes in the relative frequency with which each of the available strategies is used (dimension 2), changes in the accuracy and the speed of strategy execution (dimension 3), and changes in the adaptiveness of strategy choices (dimension 4). According to this model, at the beginning of the learning process, the learner frequently, if not exclusively, chooses rather primitive back-up strategies (like, for instance, counting), which he or she executes rather inefficiently (i.e., inaccurately and slowly), and if the repertoire contains different strategies, the learner is not able to select these different strategies in the most economical way. With experience, the learner uses more efficient back-up strategies and retrieval, which he or she executes ever more frequently, more efficiently, and also more adaptively. To obtain unbiased information about the efficiency of strategy use and the adaptiveness of individual strategy choices, Siegler and Lemaire (1997) propose the use of the “choice/nochoice” method1. This method requires testing each subject under two types of conditions. In the choice condition, subjects can freely choose which strategy they use to solve a series of problems from a given task domain. In the no-choice condition, the researcher forces them experimentally to solve all problems with one particular strategy. The number of no-choice conditions can vary according to the number of strategies available to the subject, research interests, technical possibilities, etc. Comparison of the data about the accuracy and the speed of the different strategies as gathered in the no-choice conditions, with the strategy choices made in the choice condition, allows the researcher to assess the adaptiveness of individual strategy choices in the choice condition accurately: Does the subject (in the choice condition) solve each problem by means of the strategy that leads fastest to an accurate answer to this problem, as evidenced by the information obtained in the no-choice conditions? Siegler and Lemaire (1997; Lemaire & Lecacheur, 2001a) studied the adaptive nature of adults’ strategy choices in multiplication and currency conversion tasks successfully using the choice/nochoice method. Furthermore, Lemaire and Lecacheur (2001b, 2002) applied this method to describe developmental differences in 9- and 11-year olds’ strategy use in the domain of computational estimation and spelling. Although Geary, Hamson, and Hoard (2000) and Jordan and Montani (1997) offered their subjects (second- and third-grade children, respectively) simple addition and subtraction problems in a choice as well as a forced retrieval condition, the choice/no-choice method has thus far not been used systematically to study the adaptiveness of young children’s strategy choices in the domain of early arithmetic. Previous work on strategy use in the domain of simple addition Previous studies in the domain of simple addition (e.g., Fuson, 1992; Geary, BowThomas, Liu, & Siegler, 1996; Geary & Wiley, 1991; LeFevre, Sadesky, & Bisanz, 1996; STRATEGIC COMPETENCE: SIMPLE ADDITION 277 Siegler, 1987, 1988; Siegler & Jenkins, 1989; Svenson, 1985; Svenson & Sjöberg, 1983; TAL-team, 2001) revealed that children as well as adolescents and adults use a rich diversity of back-up strategies and retrieval to solve simple additions up to 20. The children who participated in Svenson and Sjöberg’s (1983) longitudinal study (during the first three years of primary education) for instance solved these problems with multiple counting strategies, such as counting fingers and verbal counting with steps greater than one unit (“7+6=7, 9, 11, 13”). Moreover, they used a variability of decomposition strategies, such as adding up to 10 (“7+6=7+3+3=10+3=13”) and the tie strategy (“7+6=6+6+1=12+1=13”), and they retrieved the answer from long term memory (“7+6=13”). Likewise, Geary and Wiley (1991) observed that the adults who participated in their study, applied multiple back-up strategies, such as counting and decomposition strategies, as well as retrieval to solve simple additions up to 20. The results of the previously cited studies also demonstrate that children and adults use all available strategies neither equally frequently nor equally efficiently. Furthermore, with experience, the frequency of the most efficient counting and decomposition strategies and of retrieval increases, while the frequency of less efficient counting strategies decreases. Likewise, as experience increases, the accuracy and the speed of strategy execution grow too. Previous research further indicated that people adapt their strategy choices to problemspecific characteristics, such as problem difficulty: Children as well as adults prefer retrieval to solve easier problems; the more difficult the problem, the more frequently they apply a back-up strategy. Research on strategic competence in children with mathematical problems (MD; Geary, 1990, 1993; Geary & Brown, 1991; Geary, Brown, & Samaranayake, 1991; Jordan & Hanich, 2000; Jordan & Montani, 1997) finally showed that their mathematical development is, compared to the development of their normally progressing peers, not only marked by a developmental delay, but also by a more fundamental deficit. Children with MD use the same repertoire of back-up strategies and retrieval as their peers without MD, but differ in the frequency and the accuracy with which they execute these strategies. Children with MD solve simple additions up to 20 more frequently with counting strategies than their normally achieving peers, and execute these strategies less accurately than the latter. This difference in the frequency and the accuracy of counting strategies decreases as practice increases, which indicates that the development of children with MD is delayed in comparison with the development of their peers without MD. Furthermore, children with MD use retrieval less often and also less accurately than their normally achieving peers. This difference in the frequency and the accuracy of retrieval does not decrease as practice increases, which evidences that the development of children with MD is not only delayed, but also qualitatively different from the development of children without MD. Finally, Geary (1990) concluded that first-graders with MD make “rather poor strategy choices” (p. 374) in comparison with their normally achieving peers. Geary et al. (1991) and Geary and Brown (1991) did not observe any difference in the adaptiveness of individual strategy choices at older ages (second-grade and third- and fourth-grade children, respectively): Both children with MD and children without MD preferred counting strategies to solve more difficult problems, and solved the easier ones most frequently with retrieval. All above-mentioned studies provide empirical support for the validity of Siegler’s theoretical ideas about developmental changes in strategy repertoire (first dimension of the model of strategic change) and strategy frequency (second dimension) in the domain of simple addition up to 20. However, the results about the efficiency of strategy execution (third dimension) and the adaptiveness of individual strategy choices (fourth dimension) are less convincing. First of all, none of these studies applied the choice/no-choice methodology to describe (developmental changes in) the accuracy and the speed of strategy use; the efficiency of strategy execution was determined on the basis of data gathered in one free-choice condition. As argued by Siegler and Lemaire (1997), the data about the speed and the accuracy of strategies obtained in the choice condition can be biased by selection effects: A strategy that is used mainly to solve easy problems, or primarily applied by the most able subjects will seem 278 J. TORBEYNS, L. VERSCHAFFEL, & P. GHESQUIÈRE more efficiently than a strategy that is almost exclusively used to solve the most difficult problems, respectively employed most frequently by the least able subjects. Secondly, one can question the way these researchers defined and operationalised the adaptiveness criterion in their studies. They focussed on subjects’ choices between, on the one hand, retrieval, and, on the other hand, all available back-up strategies. Subjects chose adaptively between the two types of strategies if they preferred retrieval to solve the easier problems, and a back-up strategy to solve the more difficult ones. Objective data (like, for instance, the size of the given numbers in the problems, or the mean accuracy rate of the problems as gathered in a large group of subjects being asked to solve the problems in one free-choice condition), were used to specify problem difficulty. The latter definition and operationalisation of adaptive strategy choices does not fit exactly with Siegler’s idea of choosing the strategy that leads the individual fastest to an accurate answer to the problem. Indeed, Siegler’s definition of adaptive strategy choices does not just refer to deciding whether to state a retrieved answer or use a back-up strategy; it also implies choosing which of all available back-up strategies you will use, in other words, choosing between the different backup strategies. Furthermore, as stated in the definition and discussed in several publications (see, among others, Siegler & Shipley, 1995; Siegler, 1996; Siegler & Lemaire, 1997), strategy efficiency plays a major role in deciding which strategy to use; strategy choices are not merely determined by problem difficulty, but also by strategy performance characteristics. As mentioned earlier, the use of the choice/no-choice method is required to obtain reliable data about these strategy performance characteristics and thus the adaptive nature of individual strategy choices. In line with these criticisms, the major goal of our study was to analyse, by using the choice/no-choice method, the strategies young children with different mathematical ability use to solve simple additions with the bridge over 10 in terms of the four dimensions of Siegler’s model of strategic change, with special attention for the fourth dimension of this model, namely the adaptiveness of individual strategy choices. Method Participants Subjects were 77 beginning second-graders from two different mixed-sex schools for primary education in Flanders. Children from three intact classes were involved in the study. Both sexes were equally represented in the sample (41 boys, 36 girls), and the mean age of the children was 89 months (range=82-104 months). Based on their overall scores for mathematics at the end of the first grade, children were divided in three groups according to general mathematical ability. The group of strong pupils consisted of the seven strongest pupils of each class with respect to general mathematical ability (N=21), the group of weak pupils of the seven weakest children of each class with respect to general mathematical ability (N=21), and the group of moderate pupils of the other 35 children from the three classes. All children were tested in the month of November. At that moment, they all had learned how to solve simple additions with the bridge over 10. As is typically the case in elementary mathematics education in Flanders (Feys, 1995), their teachers had heavily focussed on the mastery of the strategy adding up to 10 (which involves the decomposition of one addend into two parts: One part which adds the other addend up to 10, and a rest part; e.g., “7+6=7+3+3=10+3=13”), rather than on the flexible use of a rich variety of clever calculation strategies for sums up to 20, such as the reversal strategy (which means that one changes the order of the addends before starting to count or calculate the answer to the problem; e.g., “6+7=7+6”) and the tie strategy (referring to the use of an automatised tie sum to answer the problem; e.g., “7+6=6+6+1=12+1=13”). STRATEGIC COMPETENCE: SIMPLE ADDITION 279 Materials Taking into account the literature on strategy use in the domain of simple addition up to 20, we made a distinction between three levels of strategies children can use to solve simple additions with the bridge over 10, namely retrieval, decomposition strategies, and counting strategies. Furthermore, we distinguished two clever strategies to solve simple additions with the bridge over 10, namely the reversal strategy and the tie strategy. All children were asked to solve a series of 25 simple additions up to 20. The problems were constructed from the 49 possible pair-wise combinations of the integers 3 to 9. On the basis of our distinction between three levels of strategy use and between two clever strategies, we selected five different problem types, with five problems in each type: One type of simple additions up to 10 (buffer items; e.g.: 3+4), and four types of additions with the bridge over 10 (experimental items). The latter problem types can be described as follows: (a) L+s problems, with a large first addend and a small second addend (e.g., 8+3=.), which can be solved with strategies at the three levels of strategy use, but do not favour the use of either of the two clever strategies; (b) s+L problems, with a small first addend and a large second addend (e.g., 3+8=.), which favour the use of the reversal strategy; (c) tie sums (e.g., 6+6=.), which are generally known to be memorised earlier than non-tie sums, and thus were expected to be solved more often with the retrieval strategy; and (d) almost-tie sums (e.g., 6+7=.), which elicit the use of the tie strategy. Conditions All children solved the series of 25 simple additions in three different conditions. In the first condition, the choice condition, children could solve each problem by using their preferential strategy. Immediately after solving each problem, children were asked to report verbally which strategy they had used to solve the problem. The identification of the strategies was based on the verbal reports of the children in combination with the experimenter’s observations of the behaviour of the children during problem solving. In the second condition, the adding up to 10 condition, children were experimentally forced to solve all problems with the adding up to 10 strategy. We forced them to use this strategy by means of the instruction given as well as the presentation format of the items (see below). The children were not allowed to use the reversal strategy in this condition: They had to decompose the second addend of each problem. Note that, as a consequence of the obligatory use of the adding up to 10 strategy, the five simple additions up to 10 were not administered in this condition. In the third condition, the retrieval condition, children were experimentally forced to retrieve the answer to all problems by means of the instruction given as well as the presentation time of the items. Indeed, all items were offered during maximum two seconds, which made it very difficult, if not impossible for these young children to use a strategy other than retrieval2. Procedure The children were tested individually. In each condition, problems were presented one at a time in the middle of a computer screen. Children were asked to verbally state their answer as soon as they knew it. The experimenter then entered the answer by means of the numerical path of the keyboard. After the experimenter had entered the answer, the next problem appeared on the screen. The computer registered automatically the reaction time (i.e., the time needed to solve the problem, operationalised as the time between problem appearance and the beginning of the verbal statement of the answer) and the answer to each problem. In the choice and the retrieval condition, problems were presented as follows: X+Y=. In the adding up to 10 condition, the presentation format was as follows: X+Y=X+(.+.)=.; children were 280 J. TORBEYNS, L. VERSCHAFFEL, & P. GHESQUIÈRE asked to explain how they split the second addend of each problem in the latter condition, immediately after they had stated their answer. All children solved the series of problems in the same order in the three conditions. The order of the problems was fixed on the basis of the following constraints: (a) No repetition of problem type was permitted across consecutive problems, and (b) L+s problems and tie sums were not allowed to be either preceded or followed by s+L problems respectively almost-tie sums. In each condition, the series of problems was preceded by three practice trials, which familiarized the children with the presentation format of the items as well as the testing procedure. All children first solved the problems in the choice condition. Half of the children continued with the adding up to 10 condition, and ended with the retrieval condition. For the other half of the children, the order of the two no-choice conditions was reversed. For each child, the consecutive conditions were separated in time for at least one day and at most two days. Results Results are presented for the four dimensions of Siegler’s model of strategic change 3. We start with a description of the different types of strategies the children used to solve simple additions with the bridge over 10 in the choice condition, as well as the relative frequency with which they applied these strategies (first and second dimension). Next, we discuss the accuracy and the speed of strategy execution (third dimension). Finally, we present our results about the adaptiveness of individual strategy choices (fourth dimension). We executed multilevel analyses to describe the frequency, accuracy, speed, and adaptiveness of strategy execution. We used hierarchical linear models with two levels: The higher-mentioned characteristics of strategy use (level 1) are “nested” within children (level 2). We analysed the data about the frequency and speed of strategy use by means of the so-called “proc mixed” of the computer program SAS (Littell, Milliken, & Stroup, 1996), which assumes the data to be normally distributed. Taking into account the binomial distribution of the accuracy and adaptiveness data, we analysed the latter data by means of the so-called “glimmix macro” of the same statistical program. All reported results are statistically significant at an alpha level of .05, unless otherwise noted. Strategy repertoire and strategy frequency in the choice condition In the first analysis, we predicted the frequency of strategy use in the choice condition by means of the variables level of strategy use (retrieval, decomposition, counting), group (strong, moderate, weak), and problem type (L+s, s+L, tie, almost-tie). We added the variable level of strategy use as a random coefficient to the model, which means that the influence of the latter variable on the frequency of strategy use differs from child to child. Table 1 describes the relative frequency of retrieval, decomposition, and counting strategies in the choice condition per group and per problem type (least-squares means, i.e. predicted population means). Table 1 shows that the children spontaneously applied retrieval, decomposition and counting strategies to solve simple additions with the bridge over 10. Children retrieved the answer to some problems, used a rich diversity of decomposition strategies, such as the adding up to 10 strategy, the tie strategy, the reversal strategy, and the “one less than 10” strategy (e.g., “9+5=10+5–1=15-1=14”), and applied multiple counting strategies, such as verbal counting and counting fingers. This diversity in strategy use (retrieval, decomposition, and counting strategies) was observed for the three ability groups and for the four problem types. The results in Table 1 also indicate that children did not use retrieval, decomposition, and counting strategies equally frequently (F(2,148)=48.70, p<.0001). They preferred the use of decomposition strategies, and especially the strategy adding up to 10. The latter strategy was STRATEGIC COMPETENCE: SIMPLE ADDITION 281 applied on 87% of the items that they solved by means of a decomposition strategy. Retrieval was used more often than counting strategies. Table 1 Relative frequency of strategy use in the choice condition per group and per problem type (Least-Squares Means) Retrieval Decomposition Counting Group Strong Moderate Weak All 42.84 31.29 25.83 33.32 56.05 60.29 37.44 51.26 11.11 18.43 36.73 15.42 Problem type L+s s+L Tie Almost-tie 28.40 24.59 57.62 22.67 55.62 57.88 30.97 60.57 15.98 17.53 11.41 16.76 Note. Relative frequency is expressed in percentage; L+s=Problems with a large first and a small second addend, like 8+3=.; s+L=Problems with a small first and a large second addend, like 3+8=.; Tie=Tie sum, like 6+6=.; Almosttie=Almost-tie sum, like 6+7=. Furthermore, we found strong group differences in the frequency of strategy use (F(6,666)=8.96, p<.0001). Children with strong mathematical abilities retrieved the answer to the problems more often than children with moderate and weak mathematical abilities. Children with weak mathematical abilities solved the problems less frequently with decomposition strategies than the other children, and used counting strategies more frequently than the other children. The results in Table 1 finally reveal that the frequency of strategy use differed between the four problem types (F(9,666)=26.92, p<.0001). This difference was due to the fact that tie sums were solved more often with retrieval, and less often with a decomposition strategy, than the other problem types. Strategy accuracy and strategy speed in the choice and no-choice conditions We first derived the accuracy and the speed of strategy execution in the choice condition from, respectively, the score and the reaction time in this condition. We predicted the accuracy of strategy execution by means of the variables level of strategy use (retrieval, decomposition, counting), group (strong, moderate, weak), and problem type (L+s, s+L, tie, almost-tie). We predicted the speed of strategy execution by means of the same variables, with level of strategy use and problem type as random coefficients. Table 2 describes the accuracy and the speed of strategy execution in the choice condition per group and per problem type (leastsquares means). Table 2 demonstrates that the children did not execute all strategies equally accurately in the choice condition (F(2,1425)=8.86, p=.0001). They solved the problems more accurately with retrieval or a decomposition strategy than by means of a counting strategy. The children answered the problems almost always correct when they chose freely to use retrieval or a decomposition strategy. We observed group differences in the accuracy of strategy execution in the choice condition (F(4,1425)=2.21, p=.0660; border significant). Children with strong mathematical abilities executed retrieval more accurately than children with moderate mathematical abilities, who, at their turn, applied this strategy more accurately than children with weak mathematical abilities. The latter group of children executed decomposition strategies less 282 J. TORBEYNS, L. VERSCHAFFEL, & P. GHESQUIÈRE accurately than children with strong and moderate mathematical abilities. The accuracy of strategy execution did not differ between the four problem types (F(6,1425)=1.39, p=0.2151). Table 2 Accuracy and speed of strategy execution in the choice condition per group and per problem type (Least-Squares Means) Retrieval Decomposition Counting Accuracy Speed Accuracy Speed Accuracy Speed Group Strong Moderate Weak All 0.99 0.96 0.86 0.96 2.90 2.72 3.91 3.18 0.98 0.97 0.90 0.96 5.85 5.82 7.84 6.50 0.81 0.82 0.79 0.81 10.29 17.94 11.62 19.95 Problem Type L+s s+L Tie Almost-tie 0.96 0.97 0.97 0.95 3.27 3.32 2.65 3.46 0.97 0.96 0.94 0.96 5.45 5.46 7.52 7.60 0.87 0.84 0.81 0.68 16.17 16.90 11.53 15.21 Note. Accuracy is expressed in proportion correct, speed in seconds; L+s=Problems with a large first and a small second addend, like 8+3=.; s+L=Problems with a small first and a large second addend, like 3+8=.; Tie=Tie sum, like 6+6=.; Almost-tie=Almost-tie sum, like 6+7=. Accuracy (A) and speed (S) of responding in the choice condition per group and per problem type: (a) Strong: A=0.97, S=6.35; Moderate: A=0.94, S=5.49; Weak: A=0.86, S=7.79; (b) L+s: A=0.95, S=4.96; s+L: A=0.94, S=5.23; Tie: A=0.93, S=7.23; Almost-tie: A=0.91, S=8.75 Furthermore, the children did not execute all strategies equally fast in the choice condition (F(2,93)=51.85, p<.0001). Problems were solved fastest with retrieval, and slowest with counting strategies. We observed no group differences in the speed of strategy execution in the choice condition (F(4,1098)=1.09, p=.3587). However, the speed of strategy execution differed between the four problem types (F(6,1098)=6.14, p<.0001). The children executed decomposition and counting strategies faster on L+s and s+L problems than on tie and almost-tie sums. Next, we derived the accuracy of the adding up to 10 and the retrieval strategy from the scores in, respectively, the adding up to 10 condition and the retrieval condition4. We predicted the accuracy of strategy execution in both no-choice conditions by means of the variables strategy (adding up to 10, retrieval), group (strong, moderate, weak), and problem type (L+s, s+L, tie, almost-tie). The variable strategy was added to the model as random coefficient. Table 3 presents the accuracy of strategy execution in the adding up to 10 and the retrieval condition per group and per problem type (least-squares means). Table 3 reveals that the children did not execute the adding up to 10 and the retrieval strategy equally accurately (F(1,74)=396.21, p<.0001). The children made less errors when they had to apply the adding up to 10 strategy than when they were forced to use retrieval. Moreover, we observed clear group differences in the accuracy of strategy execution in the nochoice conditions (F(2,2914)=13.95, p<.0001). Children with strong mathematical abilities applied the adding up to 10 strategy more accurately in the respective no-condition than children with moderate mathematical abilities. Children with weak mathematical abilities executed both the adding up to 10 and retrieval strategy less accurately than children with strong and moderate mathematical abilities. The accuracy of strategy execution in the nochoice conditions also differed between the four problem types (F(3,2914)=12.86, p<.0001). The adding up to 10 strategy was executed least accurately on s+L problems, and most accurately on L+s problems and tie sums. Children made least retrieval errors on tie sums; they answered L+s problems more accurately with retrieval than s+L problems (t(2914)=1.85, p=.0639; border significant) and almost-tie sums. STRATEGIC COMPETENCE: SIMPLE ADDITION 283 Table 3 Accuracy of strategy execution in the adding up to 10 and the retrieval condition per group and per problem type (Least-Squares Means) Adding up to 10 condition Retrieval condition Group Strong Moderate Weak All 0.98 0.95 0.87 0.95 0.33 0.25 0.07 0.18 Problem type L+s s+L Tie Almost-tie 0.98 0.90 0.97 0.94 0.15 0.11 0.51 0.10 Note. Accuracy is expressed in proportion correct; L+s=Problems with a large first and a small second addend, like 8+3=.; s+L=Problems with a small first and a large second addend, like 3+8=.; Tie=Tie sum, like 6+6=.; Almosttie=Almost-tie sum, like 6+7=. Adaptiveness of strategy choices in the choice condition The differences in the frequency of strategy use between the four problem types in the choice condition are a first source of evidence for the adaptive nature of children’s strategy choices in the latter condition. The children solved tie sums, which were answered more accurately than non-tie sums in the retrieval condition, in the choice condition more frequently with retrieval than the other problem types; they answered the former also less often with a decomposition strategy than the latter. This indicates that the children adapted their strategy choices to (objective) problem-specific characteristics. Starting from Siegler’s definition of an adaptive strategy choice as choosing the strategy that leads the individual fastest to an accurate answer to the problem, we further intended to describe the adaptiveness of strategy choices in the choice condition on the basis of the accuracy and the speed of the adding up to 10 and retrieval strategy in the respective nochoice conditions. However, as explained in Footnote 4, we could not gather reliable data about the speed of strategy execution in the no-choice conditions. Consequently, we had to rely on the accuracy data only. We first estimated the adaptiveness of strategy choices in the choice condition at the group level. In line with the analytic approach of Siegler and Lemaire (1997; Lemaire & Lecacheur, 2001a,b, 2002; see also Geary & Burlingham-Dubree, 1989), we calculated for each problem the correlation between, on the one hand, the relative frequency with which the strong, the moderate and the weak pupils applied retrieval, decomposition, and counting strategies in the choice condition, and, on the other hand, the accuracy with which they answered this problem in the no-choice conditions. Based upon the hypothesis that all three ability groups would at least to some extent be adaptive in their strategy choices, we expected the following correlations: 1) A positive correlation between the accuracy rate for a particular problem in the retrieval condition and the relative frequency of retrieval for that problem in the choice condition, 2) A negative correlation between the accuracy rate for a particular problem in the retrieval condition and the relative frequency of decomposition for that problem in the choice condition, 3) A negative correlation between the accuracy rate for a particular problem in the retrieval condition and the relative frequency of counting for that problem in the choice condition, 284 J. TORBEYNS, L. VERSCHAFFEL, & P. GHESQUIÈRE 4) A positive correlation between the accuracy rate for a particular problem in the adding up to 10 condition and the relative frequency of retrieval or decomposition for that problem in the choice condition, 5) A negative correlation between the accuracy rate for a particular problem in the adding up to 10 condition and the relative frequency of counting for that problem in the choice condition. The first correlation analysis revealed that the children, irrespective of their general mathematical ability, adapted their strategy choices to the accuracy with which they knew a problem by heart, as evidenced by their scores in the retrieval condition. We observed a positive correlation between the accuracy of problem solving in the retrieval condition and the frequency of retrieval in the choice condition (hypothesis 1). The more accurately the strong, the moderate, and the weak children knew a problem by heart, the more frequently they used retrieval to solve this problem in the choice condition (rstrong=0.73, p=.0002; rmoderate=0.88, p<.0001; rweak=0.75, p=.0001). As can be expected on the basis of the results of the first correlation analysis, we found a negative correlation between the accuracy of retrieval in the retrieval condition and the frequency of decomposition and counting in the choice condition (hypothesis 2 and 3). The more accurately the strong, the moderate, and the weak children knew a problem by heart, the less frequently they solved this problem by means of decomposition in the choice condition (rstrong=-0.73, p=.0003; rmoderate=-0.86, p<.0001; rweak=-0.72, p=.0003); the more accurately the children with moderate and weak mathematical abilities answered a problem in the retrieval condition, the less frequently they counted the answer to this problem in the choice condition (rstrong=-0.04, p=.8551; rmoderate=-0.61, p=.0040; rweak=-0.51, p=.0208). The children with moderate mathematical abilities took into account the accuracy of the adding up to 10 strategy too (hypotheses 4 and 5): The more accurately the moderate pupils could solve a problem with the latter strategy, as evidenced by their scores in the adding up to 10 condition, the more often they chose the retrieval or a decomposition strategy (r=0.51, p=.0204), and the less frequently they applied counting (r=-0.51, p=.0204) to solve the problem in the choice condition. We found no group differences in the strength of the correlation between the accuracy rate in the no-choice conditions and the frequency of strategy use in the choice condition. Next – and complementary to the group level analyses described above – we estimated the adaptive nature of strategy choices in the choice condition at the individual level. Therefore, we compared for each child and for each problem the accuracy of strategy execution in the adding up to 10 and the retrieval condition with the particular strategy this child had chosen to solve this specific problem in the choice condition. We formulated the following general criterion to determine the adaptive nature of strategy choices in the choice condition: A child makes an adaptive strategy choice if and only if he or she solves a problem in the choice condition with a strategy that belongs to at least the same level of strategy use as the highest level available to this child, as indicated by his or her task performance on the same problem in the adding up to 10 and the retrieval condition. We concretised this general adaptiveness criterion as follows: A child makes an adaptive strategy choice in the choice condition if he or she: 1) prefers retrieval to solve a problem he or she can answer accurately with this strategy in the retrieval condition, 2) prefers the adding up to 10 strategy to solve a problem he or she can not answer accurately with retrieval in the retrieval condition, but with the adding up to 10 strategy in the adding up to 10 condition; if the child prefers another decomposition strategy (like, for instance, the tie strategy) or retrieval to answer such a problem in the choice condition, this choice is also scored as an adaptive one, provided it resulted in a correct answer, 3) prefers a counting strategy to solve a problem he or she can not answer accurately with retrieval nor the adding up to 10 strategy in the respective no-choice conditions; if the STRATEGIC COMPETENCE: SIMPLE ADDITION 285 child prefers a decomposition strategy or retrieval to answer such a problem in the choice condition, this choice is scored as an adaptive one, provided it led to an accurate answer. The results of this data analysis at the individual level reveal clear differences in the adaptiveness of strategy choices (F(2,1428)=7.06, p=.0009). Children with strong mathematical abilities made more adaptive strategy choices than children with moderate mathematical abilities (M=89.20 and M=80.69, respectively), who, at their turn, chose more adaptively between the different types of strategies than children with weak mathematical abilities (M=70.20). The latter children frequently used a (more primitive) counting strategy to solve problems they already could solve accurately with the (more advanced) adding up to 10 strategy. Furthermore, we observed differences in the adaptiveness of individual strategy choices between the different problems (F(18,1428)=1.71, p=.0324): The children answered 9+5 least adaptively (M=67.21), and 5+6 most adaptively (M=90.97). In sum, the results of the group level analyses as well as the results of the analyses at the individual level indicate that the children were generally quite adaptive in their strategy choices in the choice condition. The group level analyses showed that children fitted their strategy choices to the accuracy of the adding up to 10 strategy and, even more, of the retrieval strategy, and revealed no group differences in the adaptiveness of strategy choices. Next, the analyses at the individual level demonstrated that children made adaptive strategy choices, and revealed that children with stronger mathematical abilities chose more adaptively between the retrieval, decomposition, and counting strategies than children with weaker mathematical abilities. Conclusions and discussion This study aimed at describing the repertoire, frequency, efficiency, and adaptiveness of the strategies second-graders apply to solve simple additions with the bridge over 10, using the choice/no-choice method. On the one hand, our study replicates the findings of previous research on strategy use in the domain of simple addition up to 20, in which empirical evidence was found for the validity of Siegler’s model of developmental changes in the repertoire and frequency of strategies. On the other hand, the results of our study deepen our insight into the efficiency of strategy execution and the adaptiveness of young children’s strategy choices, and document the value of the choice/no-choice method to determine strategy efficiency characteristics and, especially, the adaptive nature of strategy choices. In line with the results of previous research, the children who participated in our study used a rich variety of retrieval, decomposition, and counting strategies to solve simple additions with the bridge over 10. Notwithstanding the strong instructional focus on the mastery of the strategy adding up to 10, most children already were able to retrieve the answer to some problems, while applying a diversity of counting strategies on others. With respect to the decomposition strategies, the children employed the (well-trained) adding up to 10 strategy, but also, although to a much lesser extent, the (untrained) tie strategy, reversal strategy, and “one less than 10” strategy. We observed no differences in the repertoire of strategy use between children with different mathematical abilities (first dimension). With respect to the second dimension, the children did not use the different types of strategies equally frequently. They obviously preferred the adding up to 10 strategy to solve the problems. But they also used the retrieval strategy rather frequently, and applied the latter strategy more often than counting strategies. The frequency of strategy use differed clearly in function of the children’s general mathematical ability: Children with stronger mathematical abilities solved more problems with retrieval or a decomposition strategy, and solved less problems by means of counting, than children with weaker mathematical abilities. The children did not execute all strategies equally efficiently (third dimension). Retrieval 286 J. TORBEYNS, L. VERSCHAFFEL, & P. GHESQUIÈRE was executed fastest – and also very accurately – in the choice condition, and decomposition strategies were faster and more accurately than counting strategies in the latter condition. The efficiency of strategy execution in the choice condition differed between children of distinct mathematical ability. Children of the weakest ability level made more retrieval and decomposition errors than children with moderate and strong mathematical abilities, and children with moderate mathematical abilities made more retrieval errors than children of the strongest ability level. However, as stressed before, these data about the accuracy and the speed of strategy execution in the choice condition need to be interpreted cautiously. In particular, the data about the accuracy of the adding up to 10 and the retrieval strategy, obtained in the respective no-choice conditions, demonstrated that the accuracy of the retrieval strategy was probably overestimated in the choice condition due to its frequent use on tie sums, which are – and also were in our study, as evidenced by the data in the retrieval condition – memorised earlier than non-tie sums (Ashcraft, 1987; Baroody, 1987; Fuson, 1992). Moreover, the accuracy data from the no-choice conditions revealed – in contrast with those obtained in the choice condition – no differences in retrieval accuracy between children with strong and moderate mathematical abilities, but clear differences in decomposition accuracy between these groups of children. Finally, with respect to the fourth dimension, our results reveal that after one year of elementary mathematics education, Flemish second-graders are quite able to choose adaptively between retrieval, decomposition, and counting strategies while solving simple additions with the bridge over 10. First of all, the differences in the frequency of strategy use between the four problem types in the choice condition show that the children adapted their strategy choices to problem-specific characteristics. The children preferred to solve the tie sums, which, as mentioned before, are and were memorised earlier than non-tie sums, by means of retrieval. Second, the positive correlations between the accuracy with which the three ability levels applied retrieval in the retrieval condition and the frequency of retrieval, decomposition, and counting in the choice condition, illustrate the basically adaptive nature of the strategy choices too, even of those from the weakest ability level. Thirdly, the fine-grained, individualised comparison of each child’s strategy choices in the choice condition with the accuracy of problem solving in the adding up to 10 and the retrieval condition, revealed that the children made more adaptive strategy choices than non-adaptive ones (in the choice condition), and that children with stronger mathematical abilities chose more adaptively between the retrieval, decomposition, and counting strategies than children with weaker mathematical abilities. However, the latter results contradict the results of the group level analyses. These contradictory results are probably due to differences in the concretising of the adaptiveness criterion in both analyses. The individual analyses took into account the accuracy of problem solving in the no-choice conditions, as well as the accuracy of problem solving in the choice condition (see part 2 and 3 of the concretising of the criterion), whereas the group level analyses did not take into account the accuracy of problem solving in the choice condition. The latter resulted in differences between both analyses in the scoring of a choice as an adaptive or a non-adaptive one, especially in the group of weak children, which decreased the group differences in adaptiveness at the group level, and increased these differences at the individual level (for more details, see Torbeyns, Verschaffel, & Ghesquière, 2001a). From a methodological viewpoint, our study documents the value of the choice/no-choice method to gain deeper insight in the efficiency and the adaptive nature of young children’s strategy use. Above all, this method allowed us to gather unbiased information about the accuracy with which each child executed the strategy adding up to 10 and retrieval when solving simple additions with the bridge over 10, which helped us to estimate the adaptiveness of each child’s individual strategy choices in the choice condition accurately too. However, as a consequence of two practical problems, we were not able to obtain unbiased information about the efficiency of all strategies that the participating children used, which made it impossible for us to get a complete picture of the adaptiveness of each individual’s strategy choices. First of all, the children used a very rich diversity of decomposition and counting strategies to solve the problems in the choice condition. Methodological and practical STRATEGIC COMPETENCE: SIMPLE ADDITION 287 considerations, such as, the methodological (im)possibilities to guarantee that the children use the strategy they are supposed to be using in each of the required no-choice conditions, and the large amount of time it would have taken to test each child in each of these conditions, prevented us to design a no-choice condition for each of the observed strategies (for a more extensive discussion of this topic, see Torbeyns, Verschaffel, & Ghesquière, 2001b). Secondly, we were not able to gather reliable information about the speed of the adding up to 10 and the retrieval strategy to solve simple additions with the bridge over 10. As mentioned earlier, the participating children systematically answered slower in the adding up to 10 condition than in the choice condition, even on those problems they had solved freely by means of that same adding up to 10 strategy in the choice condition. The time limit in the retrieval condition made it impossible to gather reliable data about the speed of the retrieval strategy. This made it problematic to apply the information about the speed of strategy execution in our operationalisation of the adaptiveness criterion in the group level analyses as well as in the analyses at the individual level. Taking into account the theoretical strengths as well as the practical limits of the choice/no-choice method, we think it is a challenge for future research to try to reconcile Siegler’s methodological ideal with the practical constraints of a research setting, in order to further improve our understanding of the efficiency of strategy use and, ever more, the adaptive nature of children’s and adults’ strategy choices in solving mathematical tasks in particular, and in reasoning and problem solving in general. Notes 1 As argued by Siegler and Lemaire (1997) and discussed below, the information about the efficiency of strategies generated by the “choice” method are probably biased by selection effects. 2 Taking into account the results of our pilot-study and the literature concerning the topic, we reduced the maximum solution time in the retrieval condition to two seconds. Reducing the maximum solution time up to two and a half seconds, allowed the second- and third-graders who participated in our pilot-study, to use a (fast executed) decomposition or counting strategy on the problems they did not know by heart. Although a further reduction of the solution time to two seconds can neither guarantee the use of retrieval, the research literature (Baroody, 1999; Siegler, 1996) does not support the reduction of the solution time to less than two seconds. 3 In this article, we focus on the results concerning the level of strategy use (retrieval, decomposition, counting). We refer the interested reader to another publication (Torbeyns, Verschaffel, & Ghesquière, 2001a), in which these results and the results about the cleverness of strategy use are discussed in more detail. 4 Methodological and practical constraints prevented us to design a no-choice condition for each of the distinguished retrieval, decomposition, and counting strategies. Taking into account the aims, the content, and the organization of elementary mathematics education in Flanders (Feys, 1995), we asked the children to use the adding up to 10 strategy on all problems in a first no-choice condition, and the retrieval strategy in a second one. The data we obtained in the adding up to 10 and the retrieval condition are limited to the accuracy of the respective strategies. We were not able to gather reliable data about the speed of the adding up to 10 and retrieval strategy. First, children solved problems slower in the adding up to 10 condition than in the choice condition, even those problems they had answered spontaneously with this same adding up to 10 strategy in the choice condition. This is probably due to the fact that most children had already reached a stage wherein they could execute the adding up to 10 strategy in a (quasi-)automatised way (i.e., very fast and without conscious control of all steps involved) in the choice condition, whereas both the instruction and the presentation format of the problems in the adding up to 10 condition forced them to execute this strategy in a more articulated and stepwise – and therefore necessarily slower – way. Second, children were forced to answer all problems within two seconds in the retrieval condition. Whenever a child was not able to answer a problem within this time limit, the computer registered his or her answer automatically as “out of time”. References Ashcraft, M.H. (1987). 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In L Verschaffel (Chair), Strategy changes and strategy choices in children’s and adults’ mathematical thinking: Theoretical and methodological contributions. Symposium conducted at the 9th Conference of the European Association for Research on Learning and Instruction, Fribourg, Switzerland. Lemaire, P., & Lecacheur, M. (2002). Applying the choice/no-choice methodology: The case of children’s strategy use in spelling. Developmental Science, 5, 42-47. Lemaire, P., & Siegler, R.S. (1995). Four aspects of strategic change: Contributions to children’s learning of multiplication. Journal of Experimental Psychology: General, 124, 83-97. Littell, R.C., Milliken, G.A., & Stroup, W.W. (1996). SAS system for mixed models. Leuven: SAS Institute. Siegler, R.S. (1987). The perils of averaging data over strategies: An example from children’s addition. Journal of Experimental Psychology: General, 116, 250-264. Siegler, R.S. (1988). Individual differences in strategy choices: Good students, not-so-good students and perfectionists. STRATEGIC COMPETENCE: SIMPLE ADDITION 289 Child Development, 59, 833-851. Siegler, R.S. (1996). Emerging minds. New York: Oxford University Press. Siegler, R.S., & Jenkins, E.A. (1989). How children discover new strategies. Hillsdale, NJ: Erlbaum. Siegler, R.S., & Lemaire, P. (1997). Older and younger adults’ strategy choices in multiplication: Testing predictions of ASCM using the choice/no-choice method. Journal of Experimental Psychology: General, 126, 71-92. Siegler, R.S., & Shipley, C. (1995). Variation, selection and cognitive change. In T. Simon & G. Halford (Eds.), Developing cognitive competence: New approaches to process modelling (pp. 31-76). Hillsdale, NJ: Erlbaum. Svenson, O. (1985). Memory retrieval of answers of simple additions as reflected in response latencies. Acta Psychologica, 59, 285-304. Svenson, O., & Sjöberg, K. (1983). Evolution of cognitive processes for solving simple additions during the first three school years. Scandinavian Journal of Psychology, 24, 117-124. TAL-team (2001). Children learn mathematics. A learning-teaching trajectory with intermediate attainment targets for calculation with whole numbers in primary school. Groningen, The Netherlands: Wolters Noordhoff. Torbeyns, J., Verschaffel, L., & Ghesquière, P. (2001a). De brug over 10: resultaten van een exploratief onderzoek naar de keuze en toepassing van cognitieve strategieën door 6-7-jarigen (Intern Rapport) [Up over 10: Results of a study on young children’s strategy use and strategy choices (Intern Report)]. Leuven, Belgium: Katholieke Universiteit Leuven, Centrum voor Instructiepsychologie en- Technologie. Torbeyns, J., Verschaffel, L., & Ghesquière, P. (2001b). Strategieontwikkeling en strategiekeuze bij cognitieve taken. Een kritische analyse van Sieglers theorie van “strategic change” [Choice and development of cognitive strategies. A critical analysis of Siegler’s theory of “strategic change”]. Pedagogisch Tijdschrift, 26, 113-142. Dans cet article, nous examinons différentes caractéristiques des stratégies cognitives utilisées par de jeunes enfants afin de résoudre des problèmes d’addition initiale. Les stratégies sont caractérisées et étudiées d’après le cadre conceptuel et méthodologique proposé par Siegler (Lemaire & Siegler, 1995; Siegler & Lemaire, 1997). Il s’agit notamment de la variabilité, la fréquence et l’efficacité des stratégies utilisées ainsi que de la faculté d’adaptation des enfants dans la sélection de stratégie. Soixante-dix-sept élèves en deuxième année de l’école primaire ont calculé une série de 25 problèmes d’addition initiale dans 3 conditions différentes. Dans la première condition, les élèves pouvaient utiliser une stratégie à leur choix. Dans la deuxième et la troisième condition, les mêmes enfants étaient obligés à résoudre toutes les additions soit par la stratégie de décomposition jusqu’à 10 soit par la stratégie de mémorisation. Les résultats montrent que des élèves de deuxième année primaire se servent de plusieurs stratégies (la stratégie de mémorisation, décomposer, compter) selon le type de problèmes d’addition initiale. De plus, ces stratégies diffèrent selon leur fréquence et leur efficacité. Quant à la compétence mathématique des enfants, nous pouvons conclure que celle-ci n’influence pas le répertoire des stratégies utilisées, mais qu’elle a toutefois un effet substantiel sur la fréquence, l’efficacité et la faculté d’adaptation dans leur choix stratégique. Finalement, notre étude illustre la valeur du cadre méthodologique de Siegler qui permet d’étudier la faculté d’adaptation de jeunes enfants dans leurs choix stratégiques en mathématiques. Key words: Methodology, Simple addition, Strategic change. 290 J. TORBEYNS, L. VERSCHAFFEL, & P. GHESQUIÈRE Received: January 2002 Revision received: May 2002 Joke Torbeyns. Research Assistant of the Fund for Scientific Research – Flanders, Centre for Instructional Psychology and Technology, University of Leuven, Vesaliusstraat 2, B-3000 Leuven, Belgium, E-mail: [email protected] Current theme of research: Strategic aspects of elementary mathematics learning. Most relevant publications in the field of Psychology of Education: Torbeyns, J., Verschaffel, L., & Ghesquière, P. (2001). Strategieontwikkeling en strategiekeuze bij cognitieve taken. Een kritische analyse van Sieglers theorie van “strategic change” [Choice and development of cognitive strategies. A critical analysis of Siegler’s theory of “strategic change”]. Pedagogisch Tiidschrift, 26, 113-142. Torbeyns, J., Verschaffel, L., & Ghesquière, P. (2001). Investigating young children’s strategy use and task performance in the domain of simple addition, using the “choice/no-choice” method. In M. van den Heuvel-Panhuizen (Ed.), Proceedings of the 25th Conference of the International Group for the Psychology of Mathematics Education (vol. 4, pp. 273-278). Amersfoort, The Netherlands: Wilco. Torbeyns, J., Verschatfel, L., & Ghesquière, P. (2002). Efficientie en adaptiviteit van strategiegebruik bij elementaire rekensommen bestudeerd via de “choice/no-choice” methode [Efficiency and adaptiveness of strategy use in the domain of simple addition, using the “choice/no-choice” method). Pedagogische Studien, 79, 89-102. Torbeyns, J., Van den Noortgate, W., Ghesquiere, P., Verschaffel, L., Van de Rijt, B.A.M., & Van Luit, J.E.H. (in press). Development of Early Numeracy in 5- to 7-Year-Old Children. A Comparison between Flanders and The Netherlands. Educational Research and Evaluation. An International Journal on Theory and Practice. Lieven Verschaffel. Centre for Instructional Psychology and Technology, University of Leuven, Vesaliusstraat 2, B-3000 Leuven, Belgium, E-mail: [email protected] Current theme of research: Mathematics learning and teaching. Most relevant publications in the field of Psychology of Education: Verschaffel, L., Greer, B., & De Corte, E. (2000). Making sense of word problems (XVII, 203 pp.). Lisse, The Netherlands: Swets & Zeitlinger. Verschaffel, L., De Corte, E., Lamote, C., & Dhert, N. (1998). Development of a flexible strategy for the estimation of numerosity. European Journal for Psychology of Education, 13, 347-270. Verschaffel, L., De Corte, E., Lasure, S., Van Vaerenbergh, G., Bogaerts, H., & Ratinckx, E. (1999). Design and evaluation of a learning environment for mathematical modeling and problem solving in upper elementary school children. Mathematical Thinking and Learning, 1, 195-230. Pol Ghesquière. Section of Orthopedagogics, University of Leuven, Vesaliusstraat 2, B-3000 Leuven, Belgium, E-mail: [email protected] Current theme of research: Specific learning disabilities (dyslexia, dyscalculia); Special education. Most relevant publications in the field of Psychology of Education: Gadeyne, E., Ghesquière, P., & Onghena, P. (2000). The relationship between academic achievement and psychosocial functioning in pre-school and primary school children. In S. Rolus-Borgward, U. Tänzer, & M. Wittrock (Eds.), STRATEGIC COMPETENCE: SIMPLE ADDITION 291 Beeinträchtigyng des Lemens und/oder des Verhaltens – Unterschiedliche Ausdrucksformen rur ein gemeinsames Problem (pp. 287-295). Oldenburg: Carl von Ossietzky Universität, Didaktisches Zentrum. Ghesquière, P., Laurijssen, J., Ruijssenaars, W., & Onghena, P. (1999). The significance of auditory study to university students who are blind. Journal of Visual Impairment and Blindness, 93, 40-45. Swillen, A., Vandeputte, L., Cracco, J., Maes, B., Ghesquière, P., Devriendt, K., & Fryns, J.-P. (1999). Neuropsycho1ogical, learning and psychosocial profile of primary school aged children with the Velo-CardioFacial syndrome (22q11 deletion): Evidence for a Nonverbal Learning Disability? Child Neuropsychology, 5, 230-241. Van Ingelghem, M., Van Wieringen, A., Wouters, J., Vandenbussche, E., Onghena, P., & Ghesquière, P. (2001). Psychophysical evidence for a general temporal processing deficit in children with dyslexia. Neuroreport, 12, 3603-3607.
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