Kathryn L. Fletcher, Ph.D.
Norman W. Bray, Ph.D.
We would like to thank Nell Salamone and Penny Ray of Jefferson County Schools,
Jennifer Brewer of Tarrant City Schools, Jane Stewart of Saint Clair County Schools,
Elizabeth Gill of Fairfield City Schools, Cecil Teague of Midfield City Schools, Julia Alice
Rice of Homewood City Schools, and the principals, teachers, and students who
participated for their cooperation. We would also like to thank Clancy Blair, Shannon
Collins, Larry Hawk, Tracy Hawk, Kelly Van Matre, Julia Ward, and Daphne Wood for their
assistance and Ellen Cotter, Lisa Huffman and Carl McFarland for their comments on the
manuscript.
This research was supported by research grant HD19426 from the National Institute of Child Health and Human Development.
Mailing address: Department of Psychology and Civitan International Research Center, SC 313, University of Alabama at Birmingham, Birmingham, AL 35294. Phone: (205) 934-9768, FAX: (205) 975-6330. Send Internet email to: bray@cis.uab.edu
University of Miami
Department of Psychology
University of Alabama at Birmingham
Department of Psychology and Civitan International Research Center
External memory strategies (e.g., moving objects) were investigated in 95 11- and 17-year-old children with mild mental retardation and 7-, 9-, 11- and 17-year-old children without mental retardation. In an external memory task, objects were placed in specified spatial locations after hearing from 1 to 7 sentences. In the verbal memory task sentences were recalled orally. Target-oriented strategies increased with the number of sentences and were positively related to accuracy. There was no difference between children with mental retardation and their age peers in object-oriented strategies. For all groups, external strategies were used more frequently than verbal strategies and for 1, 2, and 3 sentences, the amount of overt activity (object-oriented, target-oriented, and overt verbal strategies combined) was the same. These results show that children with mental retardation have more strategy competencies than reported in studies of covert verbally-based strategies.
During the last two decades, many studies have found that individuals with mild mental retardation have deficiencies in the use of memory strategies. These have included rehearsal in sequential memory (Ellis, 1970), verbal elaboration in paired associate learning (Rowher, 1973), categorization in free recall (Kellas, Ashcraft, & Johnson, 1973), and organization of redundant verbal sequences (Spitz, 1973). Recently, Bray, Fletcher, and Turner (in press) noted that most studies that have reported strategy deficiencies have used tasks that required inferred covert verbal strategies.
This observation seems particularly important in light of studies showing that toddlers and preschool children without mental retardation use a variety of external orientation strategies even though they have deficiencies in verbal strategy use. For example, when requested to remember where an object is hidden, very young children use pointing, looking, and standing near the hiding place to remember the location of the object (DeLoache, Cassidy, & Brown, 1985; Wellman, Ritter, & Flavell, 1975). Whereas it has been widely assumed that the onset of strategy development occurs during the early school years (e.g., Brown, Bransford, Ferrara, & Campione, 1983), young children without mental retardation apparently have strategy competencies not evident when tasks requiring covert verbally-based strategies are used. This led Wellman (1990) to suggest the "revisionist" position that young children are "strategic" rather than "nonstrategic".
Similar results have been obtained for children with mild mental retardation, suggesting that they may have strategy competencies beyond those observed in studies using tasks requiring covert verbally-based strategies. Bray, Saarnio, Borges, and Hawk (in press) developed an external memory task which allowed for the manipulation of external objects to examine competencies in children with mental retardation similar to those found in toddlers and preschool children. Children with mild mental retardation (11-years-old) and children without mental retardation (7- and 11-years-old) listened to sequences of either two or four sentences (e.g.,"Put the pencil on the table; Put the eraser on the chair"), and at the end of the sequence, placed miniature objects with their specified targets. Manipulations of the objects during the delay between sentences were scored. Without prompting, the 11-year-old children with mental retardation and the 7-year-old children without mental retardation used more object-oriented external strategies (pointing, holding, and moving the objects with no orientation to the target) than the 11-year-old children without mental retardation. Although the groups differed in the probability of using an external strategy, children with and without mental retardation used the same type of object-oriented external strategies; that is, all three groups used the same tactics. Although object-oriented external strategies were not related to overall accuracy (correct object and target), they represent active attempts to remember a component of the sentences (objects) using external strategies.
When a prompt was given ("You can move the objects anywhere while you listen to the sentences"), almost all children (90%) used target-oriented external strategies (orienting the moveable objects toward the target) which were positively related to overall accuracy. Children with mental retardation modified their external strategy use to be more efficient and used the same tactics as the children without mental retardation. These results suggest that under some conditions minimal prompting rather than direct training may be sufficient to show strategy competencies in children with mental retardation.
As potentially important as the results from the Bray, Saarnio, Borges, and Hawk (in press) study may be, two possible limitations of their study need to be addressed. First, as noted by Ferretti (in press) in his comments on their paper, even though their prompt was designed to merely suggest that a strategy could be used and contained no information about how to move the objects, moving the objects was mentioned, possibly cuing the use of target-oriented strategies. Although Bray, Saarnio, and Hawk (in press) presented convincing arguments against Ferretti's point in their response, the functional nature of the prompt is an empirical issue. In the present study, the prompt used did not specifically mention movement of the objects. If the prompt used by Bray, Saarnio, Borges, and Hawk (in press) had its effect because it merely suggested that a strategy could be used, children in the present study would be expected to use target-oriented external strategies and their use should be positively related to accuracy. Second, the inference that verbal memory tasks result in less strategy use than external memory tasks was based only on comparisons across studies. In the present study, a within-subjects comparison was made between strategy use on an external memory task and a verbal memory task to determine if children with mental retardation are more likely to use external strategies than verbal strategies as suggested by Bray, Saarnio, Borges and Hawk. Because previous studies of external and verbal strategies varied in many ways, the inference of differences due to type of task were tentative.
We used an external memory task involving the placement of miniature objects similar to the one used by Bray, Saarnio, Borges, and Hawk (in press). We included two groups of children with mild mental retardation (11- and 17-years old) and four groups of children without mental retardation (7-, 9-, 11-, and 17-years old). Because the older children in Bray, Saarnio, Borges, and Hawk used more external strategies with four sentences than with two sentences, sequences of one, two, three, five, and seven sentences were used in the present study. Children listened to a story about a journey through a "haunted house". During the journey, children listened to sequences of sentences and arranged the objects according to the description provided. In the verbal memory task, sequences of tape-recorded sentences similar to those used in the external memory task were presented and children recalled the sequences orally.
In the present study the following questions were asked: (a) Given only a general prompt, will children with mental retardation differ from children without mental retardation in the frequency of external strategy use? (b) Will the external strategies used by children with and without mental retardation be related to accuracy? (c) Will children with mild mental retardation be more likely to use an external orientation strategy than a verbal strategy? and (d) Will the verbal memory task, as compared to the external memory task, be more difficult for children with mental retardation than children without mental retardation?
Subjects
The participants were 64 children without mental retardation with 16 each from first grade (M = 7.1 years; SD = 0.64), third grade (M = 8.9 years; SD = 0.53), fifth grade (M = 11.1 years; SD = 0.55), and eleventh grade classrooms (M = 17.1 years; SD = 0.62) and 31 children with mild mental retardation with 16 and 15 each from fifth- and eleventh-grade resource rooms (M = 11.9 years; SD = 0.69, and M = 17.2 years; SD = 0.69, respectively). All children were ambulatory, had normal vision (corrected or uncorrected) and normal uncorrected hearing, and attended schools in a large metropolitan area. The IQs of the children without mental retardation were not available, but all children were in their age-appropriate grade placement. The mean IQs for the 11- and 17-year-old children with mental retardation were 62.1 (SD = 10.1) and 65.4 (SD = 8.9), respectively. All IQs were based on the Wechsler Intelligence Scale for Children - Revised or the Wechsler Adult Intelligence Scale - Revised. Because all subjects were able to successfully perform the tasks, none were eliminated from the study.
Materials
A schematic of the apparatus is presented in Figure 1. The stimuli consisted of 9 small moveable objects placed in a row at the front of a 53 x 39 cm piece of white poster board (see Figure 1). The white board was attached to a wooden case containing an Amdek monitor with a 35 cm-diagonal screen. The screen, which was used to represent an imaginary room in the old house, was covered with a 5 X 5 matrix of 15 mm-diameter black velcro dots placed in a 19 x 14 cm rectangle with 45 mm between the centers of each dot on the horizontal and 32 mm on the vertical. A white plastic ghost (2 x 3 cm) was attached to the central velcro dot. Surrounding the screen was a blue (right-side) and pink (left-side) border extending approximately 11 cm from the margin of the screen (see Figure 1). A clear plexiglass sliding window (35 x 28 cm) with a yellow poster board border (48 x 40 cm) could be moved in front of the monitor to block access to the velcro dot grid yet allow the grid and the blue and pink border to be viewed.
Two Panasonic AG-180 video cameras were used to video-record each session. The first camera (face view), which was attached with a camera arm mounted to the side of the monitor case 62.5 cm from the center of the participant's chair, provided a view of the child's face. The second camera (side view), which was placed in a cabinet 137 cm to the participant's right, provided a view of the right side of the child, the white board, the objects on it, and the computer screen. A black cloth, decorated with toy stars, spider webs, and a moon, was loosely draped over both cameras and their supports. In addition to enhancing the "haunted house" effect, the cloth camouflaged the cameras; only the lenses of the cameras were visible. A Marantz PDM221 cassette tape recorder was used to present the sequences of sentences. An Apple IIe microcomputer was used to present the feedback light (48 x 39 mm) behind the appropriate velcro dot.
Each to-be-remembered sentence included a noun phrase and a prepositional phrase. The noun phrase consisted of "The" followed by one of the nine moveable objects. The prepositional phrase, which followed the noun phrase, always consisted of "is" and one of four prepositions ("above", "below", "on the pink side", and "on the blue side") followed by "the" and a second noun, either the "ghost" or one of the eight remaining moveable objects. Sequences such as "The candle is on the blue side of the ghost" and "The apple is below the candle" were presented.
Procedure
Session 1. The children were tested individually in a mobile laboratory parked on the school grounds. The memory task was embedded in a tape-recorded story. In this story, the child and an imaginary friend entered an old house, but soon the friend got lost, and a friendly ghost appeared to help find the lost friend. The child was then guided through a "haunted house" by the "friendly ghost" and attempted to remember where "magic objects" were placed in each imaginary room represented by the computer screen. After the child had heard the tape-recorded story about the haunted house, the experimenter asked the child to name each of the moveable objects. If the child gave an object name other than the one used during the sentences (e.g., saying "money" instead of "coin"), the experimenter provided the appropriate name. The child was then given a preposition familiarization task to ensure that each preposition was understood. First the experimenter stated the preposition and turned on the feedback light on the computer screen to illustrate that preposition (e.g., saying "This is above the ghost" while turning on the feedback light behind the velcro dot above the ghost). This was done for all four prepositions. The experimenter then read a sample sentence (e.g., "The coin is below the ghost") and opened the plexiglass door, allowing the child to place the object on the appropriate velcro dot on the computer screen. The feedback light was then activated. This sequence was repeated for all four prepositions.
Following the preposition familiarization, each child was told that for each imaginary room, he or she would hear tape-recorded sentences and would have to remember where to place the objects in the room (i.e., on the computer screen). Each child was told that "You can do anything that you think will help you to remember where to place the objects." Immediately before each sequence, there was a recorded message specifying the number of sentences (e.g., "There are three objects in this room."). As in Bray, Saarnio, Borges, and Hawk (in press), sentences were presented at the rate of one every seven seconds. The end of the sequence was indicated by a tone seven seconds after the beginning of the final sentence in the sequence. The experimenter then opened the plexiglass sliding window and the child placed the miniature objects on the computer screen representing the room. The experimenter then gave the child feedback by repeating each sentence orally in their order of presentation while simultaneously activating the feedback lights behind the appropriate velcro dots on the computer screen. There were three practice sequences that increased from one to three sentences.
Each child was then given 16 experimental sequences. There were three sequences with one and two sentences each, six with three sentences each, and two with five and seven sentences each.1 Each moveable object and preposition was mentioned with approximately equal frequency across sequences. Across children, eight different sentence orders were used, each involving different combinations of moveable objects, prepositions, and targets.
Session 2. The children returned to the mobile laboratory on a second day between 48 to 72 hours after the first session. It was explained that the "friendly ghost" needed the child's help to "clean out the bad ghosts" and that the objects in the house could be used to remove the bad ghosts. The experimenter then reviewed the instructions. Each child was told again that they could do anything to help themselves remember where to place the objects. Following the review of the instructions, one practice sequence with two sentences and one with three sentences were presented. The child then received 16 experimental sequences like those described for session one.
After the experimental sequences, the screen was covered with a white poster board, and all of the objects removed. Each child was informed that they would hear sequences of tape-recorded sentences and, following a delay, they were to repeat the sentences out loud exactly as they had heard them (herein called the verbal memory task). As in the external memory task, immediately before the sequence, there was a tape-recorded message specifying the number of sentences (e.g., "Now you will hear two sentences"). There were six sequences, each with two trials having one, two, or three sentences. Pilot work indicated that there would be a floor effect in recall with sentences presented at a rate of one every seven seconds, especially for sequences of three sentences, so sentences were presented at the rate of one every four seconds.
The end of the sequence was indicated by a tone that occurred four seconds after the beginning of the last sentence. Sentences were similar to those used in the external memory task (noun phrase + preposition phrase + noun phrase), but in order to make the verbal memory task distinct from the external memory task, the objects (e.g., ball, chair, cup, hammer, lamp, pencil, phone, radio, ring) and prepositions (over, under, left, and right) were different. For example, sequences such as "The lamp is over the ball"; "The chair is on the left side of the radio" were presented.2
Data Reduction
Strategy measures. The video tapes were scored for both external and verbal strategy use during both experimental sessions. The child's movements during the period following the presentation of each sentence were scored as (a) no external strategy, (b) an object-oriented external strategy (holding, pointing at, or manipulating moveable objects without orienting them toward the target), or (c) a target-oriented external strategy. The latter consisted of holding the objects up to the plexiglass window in front of the screen or arranging them around a central point on the board (or the center of their palm) in the configuration specified by the sequence of sentences. When asked, pilot subjects reported that the "center" represented the "ghost" (on the computer screen) and that the objects were arranged relative to the "ghost". The verbal strategies were scored as (a) no observable mouth movement, (b) an audible verbalization, or (c) an inaudible verbalization (with clear mouthings of object/preposition/target names). Because of the infrequent use of overt verbalizations, (b) and (c) were collapsed into one measure of verbal strategy. The external and verbal strategies were scored separately. Two independent judges scored 20% of the subjects' strategies across each sentence of the 16 sequences per session with 95% and 96% agreement and Cohen's kappas of .92 and .44, for the external and verbal strategies, respectively. The low kappa for verbal strategy use was due to the infrequent occurrence of the verbal strategy categories. The remaining subjects were scored by one of these judges. The strategy measures were the proportion of sentences in a sequence for which a strategy (object-oriented, target-oriented, verbal) was used.
Accuracy. For the external memory task, a correct response was defined as placing the specified moveable object on the screen in the location mentioned in the sentence (e.g., for the sentence "The coin is above the ghost", the coin had to be placed on the velcro dot directly above and adjacent to the ghost, not above but to the right or left side of the ghost; the appropriate placement was clarified during the preposition familiarization trials). For the verbal memory task, a correct response was defined as oral recall of the objects and preposition mentioned in a sentence in their correct relation (e.g., for "The pencil is over the eraser" the response "The eraser is over the pencil" would be scored as incorrect). In both tasks, accuracy for individual sentences was scored independently of the order mentioned in the sequence.
Analyses were conducted collapsing across the experimental sessions to examine group differences and the effects of number of sentences on frequency of verbal and external strategies and on accuracy. In this and all subsequent analyses, BMDP/386 Dynamic statistical programs were used with = .01. Post-hoc tests using the Newman-Keuls procedure used = .05. Because preliminary analyses indicated no significant gender effects, gender was omitted from all subsequent analyses.
Strategy Use on the External Memory Task
Object-oriented strategies. A mixed model analysis of variance (ANOVA) was conducted that included group as the between-subjects variable and number of sentences (1, 2, 3, 5, and 7) as the within-subjects variable. The dependent variable was the proportion of sentences for which an object-oriented strategy was used. There was a significant main effect for group, F(5,89) = 4.88, with means of .30, .29, .53, .43, .19, and .21 for 11- and 17-year-old children with mental retardation and the 7-, 9-, 11-, and 17-year-old children without mental retardation, respectively. Newman-Keuls Tests indicated that the children with mental retardation differed only from the 7-year-old children whereas the 11- and 17-year-old children without mental retardation differed from both the 7- and 9-year-old children (younger children). There was a main effect for number of sentences, F(4,356) = 70.07. Object-oriented strategy use decreased as number of sentences increased (especially for sequences greater than one) for all groups. There was also a significant group by number of sentences interaction, F(20,356) = 2.93 (see the upper panel of Figure 2) with analysis of simple effects indicating that the decrease across number of sentences was most marked for the 11- and 17-year-old children with and without mental retardation (older children).
Figure 2.
Target-oriented strategies. The factors were the same as in the analysis of object-oriented strategies. The dependent variable was the proportion of sentences for which a target-oriented strategy was used. Analyses revealed a significant main effect for group, F(5.89) = 9.12, with means of .17, .17, .14, .20, .54, and .54 for the 11- and 17-year-old children with mental retardation and the 7-, 9-, 11-, and 17-year-old children without mental retardation, respectively. Newman-Keuls Tests indicated that the children with mental retardation did not differ from the younger children and that the older children without mental retardation were different from the other groups. There was also a main effect for the number of sentences, F(4,356) = 66.79. For most groups, target-oriented strategies were used more frequently as the number of sentences increased, resulting in a group by number of sentences interaction, F(20,356) = 9.15 (see the middle panel of Figure 2). Analysis of simple effects showed significant increases in target-oriented strategies as the number of sentences increased for the 11- and 17-year-olds without mental retardation and the 17-year-olds with mental retardation, but not for the other groups. These results indicate a developmental progression towards the use of more complex and more effective external strategies for children with and without mental retardation.
Verbal strategies. The factors were the same as in the analysis of object-oriented strategies. The dependent variable was the proportion of sentences for which a verbal strategy was used, collapsed across the two types of verbal strategies. There was no main effect for group but there was a significant main effect for number of sentences, F(4,356) = 3.66, with verbal strategy use increasing as the number of sentences increased. The younger children used more verbal strategies than the older groups (especially at the five and seven sentences), resulting in a significant group by number of sentences interaction, F(20,356) = 1.97 (see the lower panel of Figure 2). Analysis of simple effects revealed that the 7- and 9-year-old children increased their use of or consistently used verbal strategies for up to five sentences, followed by a slight decrease in verbal strategies at seven sentences. Verbal strategy use, however, was still relatively low. For instance, verbal strategy use never exceeded 20% for any number of sentences for these two groups.
Accuracy on the External Memory Task
The factors were the same as in the previous analyses. The dependent variable was the proportion of sentences for which the correct object was placed in the correct position. There was a main effect for group, F(5,89) = 23.50, with means of .52, .67, .52, .68, .86, .93 for the 11- and 17-year-old children with mental retardation and the 7-, 9-, 11-, and 17-year-old children without mental retardation, respectively. Newman-Keuls Tests indicated that the 11-year-old children with mental retardation did not differ from the 7-year-old children but they differed from all other groups. The 17-year-old children with mental retardation did not differ from the 9-year-old children but they differed from all other groups. The older children without mental retardation were not different from each other. There was also a main effect for the number of sentences, F(4,356) = 200.23, with accuracy decreasing as the number of sentences increased and a significant interaction of group and number of sentences, F(20,356) = 7.94. Analysis of simple effects indicated that accuracy decreased significantly as the number of sentences increased for all groups. For groups that used target-oriented strategies frequently (e.g., 17-year-olds without mental retardation), the decrease was less marked.
Strategy and Accuracy Relationships
For the external memory task, correlations between accuracy and the proportion of the use of the three types of strategies (object-oriented, target-oriented, and verbal) were computed for the younger children without mental retardation (7-and 9-year-olds), the older children without mental retardation (11- and 17-year-olds), and the children with mental retardation (see Table 1). Because accuracy for one and two sentences was consistently high, only sequences of three, five, and seven sentences were used.
Object-oriented strategies were not related to recall, indicating that these strategies did not facilitate performance on the external memory task. The target-oriented strategies had the strongest and most consistent correlation with accuracy for all groups, with the magnitude of the correlation increasing with the number of sentences. The verbal strategies were related to recall only for the younger children without mental retardation, with this relationship significant for five sentences and approaching significance for seven.
Table 1.
External Memory versus Verbal Memory
Strategy Use. Because the verbal memory task required recall for a maximum of three sentences, external memory task data were taken from sequences with one, two, and three sentences. A mixed model ANOVA was conducted that included group as a between-subjects variable and number of sentences (1, 2, and 3) and task (verbal memory task and external memory task) as within-subjects variables. The dependent variable was the proportion of sentences for which an overt strategy was used (the proportion of sentences with a verbal strategy in the verbal memory task and the sum of the proportion of sentences with object-oriented and target-oriented strategies in the external memory task).
For all groups, overall strategy use was strikingly higher on the external memory task than the verbal memory task (see Figure 3), resulting in a significant main effect for task, F(1,89) = 250.69. The main effect for group was not significant, F(5,89) = 1.53, p > .19, with means of .29, .25, .39, .40, .41 and .35, for the 11- and 17-year old children with mental retardation and the 7-, 9-, 11-, and 17-year-old children without mental retardation, respectively. This was an unexpected result that indicates that the overall level of overt activity is equivalent on the average strategy measure for the two tasks. There was also a significant task by number of sentences interaction, F(2,178) = 5.25.3, with external strategies decreasing as the number of sentences increased. The interaction of group, task, and number of sentences shown in Figure 3 was not statistically significant but is shown to illustrate the effects across groups.
Figure 3.
Accuracy. The dependent variable was the proportion of sentences on which all information in a sentence was correctly reconstructed (verbal recall in the verbal memory task and placement of an object in its correct position in the external memory task). As in the analyses of accuracy in the external memory task, there was a main effect for group, F(5,89) = 16.25. The means may be derived from Figure 4. The analysis of simple effects and post-hoc tests across the two tasks showed the same pattern of differences as for accuracy in the external memory task. Accuracy significantly decreased as the number of sentences increased for both tasks, F(2,178) = 490.43, and there was a significant group by number of sentences interaction, F(10,178) = 4.71. Analysis of simple effects showed that this decrease was greatest in the children with mental retardation and the 7- and 9-year-old children without mental retardation (see Figure 4). There was also a significant task by number of sentences interaction, F(2,178) = 80.74 (see Figure 4). Analysis of simple effects revealed that accuracy significantly decreased as number of sentences increased for both tasks; however, the decrease was more marked in the verbal memory task than in the external memory task. The interaction of group, task, and number of sentences shown in Figure 4 was not statistically significant but is shown to illustrate the effects across groups.
Figure 4.
In the present study, children with mental retardation used target-oriented strategies consisting of complex arrangement patterns. Like their age peers, the 17-year-old children with mental retardation were more likely to use these strategies as the number of sentences increased. The use of target-oriented strategies was highly correlated with recall, demonstrating that when children with mental retardation devised a target-oriented strategy, it was effective. These results were obtained using a more general prompt than used by Bray, Saarnio, Borges, and Hawk (in press), thereby showing that the results of the prior study were not an artifact of the prompt as suggested by Ferretti (in press). The present study and that of Bray, Saarnio, Borges, and Hawk contrast markedly with previous ones that have found strategy deficiencies in individuals with mental retardation. Although children with mental retardation used target-oriented strategies related to accuracy, it is important to note that, as the number of sentences increased, they decreased their use of object-oriented strategies (which were unrelated to accuracy). The children with mental retardation did not differ from their age peers in frequency of object-oriented strategies. Further, the 17-year-old children with mental retardation and the 11-and 17-year-old children without mental retardation appeared to rely more on the use of target-oriented strategies as the number of sentences increased, than on object-oriented or verbal strategies. In this situation, the children with mental retardation appear to monitor the use of less effective strategies in a manner similar to their age peers without mental retardation. These results suggest that children with mental retardation are capable of using monitoring skills not observed in research on covert verbally-based metacognitive skills.
One unexpected result was that in the comparison of the external and verbal memory tasks overall overt activity (object-oriented and target-oriented strategies on the external memory task and verbal strategies on the verbal memory task) did not differ among the groups. A supplementary analysis, however, showed that there were group differences when object-oriented, target-oriented, and verbal strategies were combined into one measure of overt activity on the external memory task with five and seven sentences (see Figure 2 for means). These findings indicate that with relatively few sentences, the overall amount of strategy use does not vary within the intelligence and age range included in this study.
The results of this study indicate that strategy use is not a fixed characteristic or trait of the individual, it varies with the nature of the task and, for all groups, is considerably more likely in an external than a verbal memory task (Bray, Fletcher, & Turner, in press). This finding is consistent with the hypothesis that nearly all prior research on memory strategies involving children with mental retardation has used tasks that do not optimize childrens' memory capabilities. By focusing on tasks requiring covert verbally-based strategies, prior studies may have misrepresented the memory capabilities of children with mental retardation. Bray and Turner (1986) noted that most verbally-based tasks used to study strategy abilities in individuals with mental retardation share several features. These include constraints on study behavior, a fast presentation rate, and relatively little explanation of the task procedure. In previous studies, these general task factors as well as the verbal nature of the tasks may have played a role in creating less-than-optimal conditions for strategy use in individuals with mental retardation. In our external memory task, each of these factors were minimized, resulting in a situation that was more supportive of strategy use.
It might be argued that the verbal memory task and the external memory task differed in other subtle ways that may have resulted in the higher frequency of external strategy use. The first argument might be that because the external memory task was embedded in a game-like story, the children may have been more motivated in the external memory task than in the verbal memory task. This explanation seems unlikely, however, because Bray, Saarnio, Borges, and Hawk (in press) observed the use of external strategies by children with mental retardation in a task with no game-like story.
A second argument might be that the external memory task had more sequences than the verbal memory task so that the children received more practice on the external memory task (24 sequences with one, two, and three sentences) as compared to the verbal memory task (6 sequences with one, two, and three sentences). To address this argument, a supplementary analysis was conducted using only the first 6 sequences of the external memory task for one, two, and three sentences (with two sequences for each number of sentences as in the verbal memory task). Even when the number of sequences in the external and verbal memory tasks were equated, there was a significant effect for task, F(1,88) = 149.23, p < .001, and strategy use in children with mental retardation was still substantially greater in the external memory task than the verbal memory task (M = .38 and .06, respectively). It is unlikely that the number of sequences in the external memory task resulted in more frequent strategy use.
A third argument might be that because verbal strategies can be covert or overt, our measure of overt verbalization may have underestimated the frequency of verbal strategies. Although this seems possible, the underestimation would have to be as great as 35% to 50%, which is the range of differences observed in overt verbal and external strategy use for the children with mental retardation (see Figure 3). In light of previous studies showing apparent strategy deficiencies in children with mental retardation using tasks requiring covert verbally-based strategies, this degree of underestimation seems very unlikely. Even allowing for some underestimation, the overt verbalization measure is a more direct measure than many of those used in previous studies of inferred verbal strategy use with individuals with mental retardation including measures of primacy effects, the effects of filled versus unfilled retention intervals, differences due to presentation rate, and pause-time patterns (see Bray & Turner, 1986, for a review).
Bray, Fletcher, and Turner (in press), noted that relatively few studies of memory strategies have included children with mental retardation in more than one age group. Of those that have, virtually all have shown a developmental increase in strategy capabilities (e.g., Bray, Hersh, & Turner, 1985; Brown & Barclay, 1976; Turner, Hale, & Borkowski, 1993). Our results are consistent with these previous studies, showing a developmental progression in external strategy use from 11 to 17 years of age in children with mild mental retardation. The 17-year-old children with mental retardation were more accurate in the external memory task and their use of target-oriented strategies increased more with the number of sentences as compared to the 11-year-old children with mental retardation. The present study and that of Bray, Saarnio, Borges, and Hawk (in press) provide strong evidence that prior research has overlooked substantial areas of strategy competency in children with mental retardation. This is not to say that individuals with mental retardation do not also have areas of weakness. In fact, to the extent that deficit theories of mental retardation postulate areas of strength and weakness, our results support a deficit position rather than the developmental theory of mental retardation advanced by Zigler (1969) and his colleagues. However, as Bray, Fletcher, and Turner (in press) contend, to understand strategy capabilities, investigators must more fully explore developmental changes in both the strengths and the weakness of individuals with mental retardation rather than focusing nearly exclusively on their deficits.
Bray, N. W., Fletcher, K. L., & Turner, L. A. (in press). Cognitive competencies and strategy use in individuals with mild mental retardation. In W. E. MacLean, Jr. (Ed.), Handbook of mental deficiency, psychological theory and research (3rd ed.). Hillsdale, NJ: Lawrence Erlbaum.
Bray, N. W., Hersh, R. E., & Turner, L. A. (1985). Selective remembering during adolescence. Developmental Psychology, 21, 290-294.
Bray, N. W., Saarnio, D. A., Borges, L. M., & Hawk, L. W. (in press). Intellectual and developmental differences in external memory strategies. American Journal on Mental Retardation.
Bray, N. W., Saarnio, D. A., & Hawk, L. W. (in press). A context for understanding intellectual and developmental differences in strategy competencies. American Journal on Mental Retardation.
Bray, N. W., & Turner, L. A. (1986). The rehearsal deficit hypothesis. In N. R. Ellis & N. W. Bray (Eds.), International review of research in mental retardation (Vol. 14, pp. 47-71). New York: Academic Press.
Brown, A. L., & Barclay, C. R. (1976). The effects of training specific mnemonics on the metamnemonic efficiency of retarded children. Child Development, 47, 71-80.
Brown, A. L., Bransford, J. D., Ferrara, R. A., & Campione, J. C. (1983). Learning, remembering and understanding. In J. H. Flavell & E. M. Markman (Eds.), Handbook of child psychology (4th ed., pp. 77-166). New York: Wiley.
DeLoache, J. S., Cassidy, D. J., & Brown, A. L. (1985). Precursors of mnemonic strategies in very young children's memory. Child Development, 56, 125-137.
* Ellis, N. R. (1970). Memory processes in retardates and normals. In N. R. Ellis (Ed.), International review of research in mental retardation (Vol. 4, pp. 1-32). New York: Academic Press.
Ferretti, R. P. (in press). Cognitive, social, and contextual determinants of strategy production: Comments on Bray, Saarnio, Borges, & Hawk's Intellectual and developmental differences in external memory strategies. American Journal on Mental Retardation.
Kellas, G., Ashcraft, M. H., & Johnson, N. S. (1973). Rehearsal processes in the short-term memory performance of mildly retarded adolescents. American Journal of Mental Deficiency, 77, 670-679.
Rowher, W. D. (1973). Elaboration and learning in childhood and adolescence. In H. W. Reese (Ed.), Advances in child development and behavior (Vol. 8., pp 2-57). New York: Academic Press.
Spitz, H. H. (1973). The channel capacity of educable mental retardates. In D. K. Routh (Ed.), The experimental psychology of mental retardation (pp. 133-156). Chicago: Aldine.
Turner, L. A., Hale, C., & Borkowski, J. G. (1993). The influence of intelligence on memory development. Manuscript submitted for publication.
Wellman, H. M. (1990). The child's theory of mind. Cambridge, MA: MIT Press.
Wellman, H. M., Ritter, K., & Flavell, J. H. (1975). Deliberate memory behavior in the delayed reactions of very young children. Developmental Psychology, 11, 780-787.
Zigler, E. (1969). Developmental versus difference theories of mental retardation and the problem of motivation. American Journal of Mental Deficiency, 73, 536-556.
1The data reported in this paper are a subset of data generated in a larger project. The children received 16 experimental sequences each session; however, four sequences with three sentences each were excluded from each session in the analyses reported in this paper because they were in a discontinuous format. In this format, sentences such as "The apple is above the ghost" followed by "The broom is above the coin" were presented. All sequences analyzed in this paper contained a continuous sentence format such as "The apple is above the ghost" followed by "The broom is on the blue side of the apple". Although discontinuous sentences were excluded from analyses in this paper, the use of external strategies on these sequences was similar to that obtained for continuous sentences. There were more sequences with one, two, and three sentences than with five and seven sentences to ensure some success for the younger children.
2In the larger study, the 16 experimental sequences on the external memory task were followed by a backward digit-span memory test. This was followed by the verbal memory task. All children were then given two unstructured interview questions (about what they did to help themselves remember during the verbal memory task and the external memory task) and several structured interview questions (cards depicting children using various strategies were presented and children were asked to pick the strategies they had used). The backward digit-span data and the interview data are not reported in this paper. Also, following each sequence of sentences in the external memory task, half of the children in the larger study were given a trial-by-trial interview in which they were asked what they did to help themselves remember. These childrens' data are not reported in this paper. 3In the verbal memory task, sentences were presented at the rate of one every four seconds; in the external memory task, one every seven seconds. In a pilot study, accuracy was very low when the sentences in the verbal memory task were presented at the rate of one every seven seconds, especially for three sentences. However, one might argue that by decreasing the time between sentences in the present study, we might have reduced the opportunity for verbal strategy use. To examine this possibility, eleven additional 11-year-old children without mental retardation were given the verbal memory task with sentences presented at the rate of one sentence every seven seconds. The additional children used verbal strategies on only 15% of the sentences, whereas the 11-year-old children in the present study used verbal strategies on 10% of the sentences in the verbal memory task and external strategies on 60% of the sentences in the external memory task.