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Frequency judgment accuracy as a function of age and school achievement (learning disabled versus non-learning-disabled) patterns
JOURNAL
OF EXPERIMENrAL
CHILD
35, 236-247 (1983)
PSYCHOLOGY
Frequency Judgment Accuracy as a Function of Age and School Achievement (Learning Disabled versus Non-Learning-Disabled) Patterns ARNOLD M. LUND Bell Laboratories JAMES W. HALL Northwestern
University
KIM P. WILSON Northwestern
University
AND MICHAEL
S. HUMPHREYS
The University of Queensland The accuracy of children’s judgments of relative situational frequency was examined in two experiments. In Experiment 1 children with normal achievement in Grades 2 and 3 were compared with such children in Grades K and 5, as well as with three groups of low-achieving children in Grades 2 and 3. These latter groups consisted of children low in reading achievement, those low in math achievement, and those identified as learning disabled. Frequency judgment accuracy increased from kindergarten to Grades 2 and 3. No other comparisons yielded significant differences. Experiment 2 confirmed both the above age difference and the absence of any frequency judgment deficiency on the part of the low-achieving groups.
Human ability to remember the frequency with which particular events have occurred has received considerable attention in recent years. Adults This research was supported by a research contract from the Bureau of Education for the Handicapped, Office of Education (US HEW OE 300 770 493) for the Chicago Institute for Learning Disabilities of the University of Illinois. We are grateful to the Evanston, Illinois school officials, teachers, and children whose cooperation made this research possible. Requests for reprints should be addressed to Arnold M. Lund, Bell Laboratories, Crawford Corner Road, Holmdel, NJ 07733. 236 0022-0965183 $3.00 CopyrIght All right\
‘Q 1983 by Academic Pres\. of reproduction in any form
Inc. reserved.
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can estimate with considerable accuracy the frequency with which particular words have occurred within a list (Hintzman, 1969), the frequency with which particular words (Shapiro, 1969), letters (Attneave, 1953), and pairs of letters (Underwood, 1971) occur in the English language, and even the frequencies of various lethal events (Lichtenstein, Slavic, Fischoff, Layman, & Combs, 1978). That ability has been implicated in recognition decisions (Underwood, 1971, 1972), verbal discrimination learning (Ekstrand, Wallace, & Underwood, 1966), probability learning (Estes, 1976), and concept formation (Bourne, Ekstrand, Lovallo, Kellogg, Hiew, & Yaroush, 1976). Hasher and Zacks (1979) have proposed an account of memory for event frequency that stresses the automaticity of processing such information. Their conclusions regarding developmental differences (or the lack thereof) are especially pertinent to the present paper: “While children become more proficient at overt and covert rehearsing, at elaborating, at imaging, at naming pictures, and at a knowledge about their own memory skills, frequency sensitivity appears to be one of those rare skills that is outside of this domain” (Hasher & Zacks, 1979, p. 370). The evidence in direct support of that conclusion derived from two experiments, both of which failed to reveal age related changes in the accuracy of frequency judgments. In one of these (Hasher & Chromiak, 1977) children in Grade 2 were compared with college students and in the second (Hasher & Zacks, 1979), children in Grades K, 1, 2, and 3 were compared. In neither case was any effort made to reduce the differences in encoding activities that ordinarily are found across this age range. It appears, then, that the absence of age differences in frequency judgment accuracy occurred despite the presence of age differences in encoding activities of the sort enumerated above. Thus, Hasher and Zacks were led to the conclusion that the processing of event frequency is independent of variations in strategic encoding activities and that humans are “genetically prepared” to efficiently process such information. Results in conflict with those of Hasher and her coworkers were obtained by Ghatala and Levin (1973, Experiment I), who in an earlier study examined both absolute and relative frequency judgments by children in Grades K, 3, and 5. (In the absolute judgment procedure, used also in the Hasher studies, test items are presented singly with the subject required to estimate the number of times the item had occurred in a study list; for the relative judgment test, pairs of study items are presented, with the subject required to indicate which items within each pair had occurred more frequently.) The Ghatala and Levin results indicated a developmental increase in the accuracy of both kinds of judgments, although the difference between Grades 3 and 5 was so slight as to suggest that a “true” developmental difference may be confined to
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the younger age period. There are, then, two published studies regarding the issue of developmental differences in frequency judgment accuracy across the very early school years, and these results are in direct conflict. Hasher and Chromiak dismissed the positive findings reported by Ghatala and Levin on the grounds of “a complex and contradictory pattern of results” and “a number of methodological problems” (Hasher & Chromiak, 1977, p. 179). However, given the relative paucity of evidence on the point, and the conflict between the relevant studies, it seems to us most reasonable to consider the matter unsettled at present. One of the two major goals of the present experiment is to provide a more definitive basis for a conclusion on the issue of developmental differences in frequency judgment accuracy across the early school years. The second main issue addressed in these experiments was the possibility of a deficiency in frequency judgment accuracy on the part of groups of children who might be characterized as learning disabled (LD). There were three groups of such children. One group consisted of children formally identified by school personnel as learning disabled. The second group was not formally identified as LD but displayed a specific deficiency in reading achievement. The third group also was not formally identified as LD but displayed low achievement specific to mathematics. Frequency judgment accuracy appears to be one of the few tasks that has received little use in the study of LD children. The only such study we have found is an unpublished one by Goldstein, Kosteski, Hasher. and Edelman (Note 1) in which no difference was found in the ability to discriminate among items varying in situational frequency. As with so many studies of LD children, however, no effort was made to isolate groups in which there was a commonality of specific achievement problems (e.g., reading difficulty). Such distinctions are desirable, because it seems quite likely that cognitive factors underlying reading difficulties may differ substantially from those that produce difficulties in mathematics, for example. To illustrate, and especially pertinent to the present experiments, it has been proposed that children with reading disabilities may suffer from inadequate knowledge of information about the frequency with which particular letters and combinations of letters occupy various positions in English words (Mason, 1975). One possible cause of such an information deficiency would be a deficiency in the processing of frequency information. A distinctive feature of our experiments was in the nature of the items to be judged. In previous studies involving very young children the procedure was to use pictures of common objects, with some objects occurring once, some twice, etc. Thus, for example, a ball might be seen once and a house twice, with the subject subsequently asked to judge which of the two had occurred more often. In the present experiments, in addition to such pairs (e.g., a white house and a yellow ball), there
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also were items that differed only in color (following a procedure introduced by Lund & Wilson, Note 2). For example, a brown kite appeared twice and a white kite once. Accuracy of relative frequency judgments to this pair would require a frequency code that is separate for two versions (colors) of the same semantic category (kite). One might expect the latter decision to be more difficult than in the case in which items differed in both category and color (white house vs yellow ball). Therefore, it might be more sensitive to the individual difference variables of concern here than were past experiments. Experiment 1 examined frequency judgment accuracy of children in Grades K, 2, 3, and 5. In addition, the three low-achievement subgroups described above were compared to the normal achievement children in Grades 2 and 3. Experiment 2 was a somewhat modified replication of Experiment 1. A relative judgment procedure was used throughout, in contrast to the absolute judgment procedure used by Hasher and Chromiak (1977) and Hasher and Zacks (1979). Although there was no a priori reason to expect that this procedure would be more sensitive to age differences, it remained a possibility worth examining. EXPERIMENT
1
Method Subjects. Six groups of public elementary school children (total N = 146) participated in the study. Four groups were drawn from Grades 2 and 3. Achievement and general intelligence test data along with other descriptive information for these groups are summarized in Table 1. One of these groups consisted of 28 children identified through school procedures as learning disabled (LD). The school district’s formal guidelines for such identification were consistent with those in common use, specifying the presence of a discrepancy between academic aptitude and academic achievement for which the probable cause is some specific cognitive processing deficit. In fact, however, in practice there is considerable ambiguity and subjectivity in the identification procedures, and one cannot be entirely certain just what population is being sampled in any given instance. Partly for that reason, and partly because such an LD group can be expected to be highly heterogeneous in the nature of their academic difficulties, both a low reading and a low mathematics (math) group were identified and included in the study. Although LD children often are assumed to be of normal intelligence but with a specific area of achievement difficulty, our data indicated otherwise for most of these school-identified LD children, Instead, most of these children were low in general intelligence as well as in achievement in both reading and math, with somewhat lower achievement in reading. The low reading group consisted of 27 children selected by virtue of reading scores at least two stanines below math achievement scores, and
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LUND ET AL. TABLE CHARACTERISTICS
Measure N CA (years) M
SD Sex (M/F) Brief cog” M
SD
OF GRADES
1
2 AND
3 SAMPLES
IN EXPERIMENT
1
Normal achievers
School learning disabled
Low reading
32
28
21
12
8.12
8.61
8.14
.66
.73
1804
.76 2018
7.94 .59 418
106.03 14.16
85.35 11.22
103.76
11.41
12.36
106 13.77
80 10.67
90 9.48
109 12.62
108 13.58
86
112
11.09
11.47
89 8.88
1819
Low math
102.83
Rdng Ach”
M SD Math Ach
M SD
Note. Brief cog, Brief Cognitive scales of the Woodcock-Johnson; achievement; Math ach, mathematics achievement. ’ Population M = 100, SD = 15.
Rdng ach, reading
where general intelligence scores were closer to the math than to the reading scores. The 12 low math children were at least two stanines lower in math than in reading, with general intelligence scores roughly in line with reading scores. The reading-math discrepancies were based on two sets of achievement test scores, one from the California Achievement Test and one from the Woodcock-Johnson Psycho-Educational Battery. Only the Woodcock-Johnson scores are shown in Table 1. The general intelligence estimates were derived from the Brief Cognitive scale of the Woodcock-Johnson. Four of the low reading children and two of the low math children whom we identified also were among the 28 children whom the schools identified as LD, producing some overlapping membership among these three groups. The fourth group, the normal achievers, consisted of 32 children chosen unsystematically except to exclude children with large reading-math discrepancies and those with general intelligence below the normal range. The 32 kindergarten (chronological age (CA) mean = 5.61, SD = .33) and 21 Grade 5 (CA mean = 10.42, SD = .44) children were selected randomly from classrooms at that level except to exclude children with obvious (by teacher judgments) handicaps. There were 13 boys and 19 girls in the kindergarten sample and 15 boys and 6 girls at Grade 5. Achievement and intelligence test data were not available for the kindergarten and Grade 5 children. Design and material. The experiment consisted of two distinct aspects, the first involving comparisons of frequency judgment accuracy among
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the normal achievers at the three age levels, and the second consisting of comparisons among the four achievement groups at Grades 2 and 3. The normal achieving children in Grades 2 and 3 participated in both sets of comparisons. Following a presentation of a series of pictures for which he produced labels (the study phases), each child was presented a set of test pairs, the pictures in each pair having occurred differing numbers of times during study presentation. A relative frequency judgment was required for each pair. Pair frequencies of one versus two, two versus three, and one versus three occurred equally often during testing. Within each pair frequency level half the picture pairs differed both in the objects’ semantic categories and in their color, for example, a white house and a yellow ball. These are termed the object and color items. The remaining half, the color only items, consisted of pairs in which the object was the same except for a difference in color, for example, a brown kite and a white kite. Two forms of the study list were constructed, each consisting of 78 pictures and each following the same format. Each set contained 12 pictures that appeared once, 12 that appeared twice, and 12 that appeared three times, plus three buffer pictures at the beginning and three at the end of the set. Within each subset of pictures at a given frequency level, six were of the object-color and six of the color only type. The pictures were line drawings of common objects colored red, white, brown, blue, yellow, or black. Each color occurred equally often at each frequency level and as the correct item in the test pairs. Inappropriate color-object pairings (e.g., a red cat) were not used. With these restrictions items were assigned randomly to frequency levels. Item order was random except that the same object never occurred on successive cards. Test pairs were evenly divided among the frequency combinations one-two, two-three, and one-three, half of each being object + color and half color only pairs. Thus, there were 3 one-two object + color pairs, 3 one-two color only pairs, 3 two-three object + color pairs, and so on, Order of test pairs was random. Procedure. To enhance motivation and attention, especially among the younger children, a game format was used in which a cartoon figure of a clown was displayed. The clown’s nose was prominent and the child was urged to make it grow even more. This could be done by correctly naming aloud the object and its color in each picture during the study period and by a correct relative frequency judgment during the test phase. In each case the experimenter intermittently placed a red chip on the nose of the clown. Each session began with an explanation of the “game,” followed by a brief test to ensure that the child understood the rules and could identify the colors used. Following a brief practice list the study list was presented at approximately 4 set per picture, with hints given on those rare occasions
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on which the child displayed hesitation in identifying an object or its color. The final forced-choice relative frequency judgment test was unpaced: The child simply was asked to indicate which of the two verbally described pictures had appeared more often during the study period. Results and Discussion Performance means are shown on the left in Table 2 collapsed over list form and frequency level. Four unequal-number ANOVAs were performed. In the first of these, four variables entered the analysis: groups (normal achievers in Grades K, 2, 3, and 5), frequency (one-two, two-three, and one-three), item type (object + color vs color only), and list form. In the three remaining analyses each of the three lowachievement groups was compared in turn with the normal achievers at Grades 2 and 3, and again the variables of frequency, item type, and list form were entered into the analyses. The low-achievement groups were treated separately here because of the marked differences in the operational criteria by which they were defined. Since there was no systematic effect of list form, and since list form was of no inherent interest, it will not be considered further. For all analyses significance was accepted at the .05 level. The results pertaining to age differences will be considered first. As may be seen in Table 2, kindergartners were less accurate overall than were the older two groups, the latter displaying nearly equal performance, with a slight edge to the Grades 2 and 3 children. This was confirmed by a significant effect of age, F(2, 79) = 7.61, MS, = 736. As expected, the color only items were more difficult than the object TABLE 2 MEAN NUMBER OF ERRORS~IN EXPERIMENTS 1 AND 2 Experiment
1
Experiment 2
Group achievement
Grade
Object + color
Color only
Object + color
Color only
Normal Normal Normal School LD Low rd Low math
K 2, 3b 5 2, 3b 2, 3b 2, 3b
.68 .33 .35 s2 .33 .58
1.33 1.03 1.13 1.01 1.21 1.06
1.63 1.08 1.33 1.08 1.10
2.08 1.83 1.95 2.00 1.75
Note. LD, learning disabled; rd, reading. ” The means within cells are based on a total of three possible errors per subject in Experiment 1 and on 6 per subject in Experiment 2. b In Experiment 1 these groups consisted of children in Grades 2 and 3; in Experiment 2 they comprised children in Grade 3 only.
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+ color items, F(1, 78) = 110.72, MS, = .507. (Both of these patterns of results were found for each form of the list.) This was consistent with the assumption that an additional encoding process, the formation of an association between color and object name, is required for the successful discrimination of the color only test items. The main effect of frequency levels also was reliable, F(2, 158) = 7.68, MS, = .425. Here, in accord with Weber’s Law, it was most difficult to discriminate between the two-three items and least difficult for the one-three items. The above results were consistent with those reported earlier by Ghatala and Levin (1973), and contrary to those of Hasher and Zacks (1979) in their indication of an age difference in frequency judgments across the first few school years. In finding no difference between the children in Grades 2, 3, and 5 they are consistent with the Hasher and Chromiak (1977) findings. We had expected that the color only items might be more sensitive to age differences, but in fact the age difference reported above did not vary with item type. The remaining three analyses involved a comparison of the normal Grade 2 and 3 children with each of the low-achievement groups in turn. The results are straightforward; although the low math group in particular was somewhat less accurate than the normal achievers, none of these comparisons showed a reliable group difference. Again in these analyses the effects of frequency difference were significant and the differences followed the same pattern as reported for the developmental comparison. The F’s(2, 112) ranged from 6.64 to 8.12 for the frequency variable, MS, from .375 to .398. For the item type variable the values of F( 1, 56) ranged from 49.89 to 100.38, and the MS, from .362 to .474. In Experiment 2 a modified replication of Experiment 1 was performed. This was done for two reasons. First, age differences in frequency judgment accuracy had been in serious question. In fact, the absence of such differences played a prominent role in arguments by Hasher & Zacks (1979) for the automaticity of event frequency processing. It seemed prudent, therefore, to be quite certain of our results. Second, there was a hint of a possible difference between the normal achievers and the low math children (see Table 2) that appeared to warrant additional investigation. EXPERIMENT
2
Method Subject and design. In Experiment 2 the developmental comparison was confined to two age-grade levels (Grades K and 3). Again, comparisons also were made between normal achievers and school-identified LD, low reading, and low math groups, this time at Grade 3. Other than the grade level difference, these four groups were defined as in Experiment 1; their relative achievement and intelligence levels differed only
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ET AL.
slightly from the previous groups. Of the 88 children participating in Experiment 2, 20 were school-identified LD, eighteen were low reading, 10 were low math, and 20 each for the normal Grade 3 and the kindergarten groups. The design was the same as for Experiment 1 except that only one versus two and two versus three frequency pairs were presented during the test phase and only a single form of the picture set was used. Materials and procedure. Each child received, in succession, two study-test picture sets, each consisting of 24 different pictures plus six buffers. Of the 24 target pictures, 6 appeared once, 12 twice, and 6 three times. The procedure was identical to that in the first experiment except that instead of receiving one 78-item study list followed by a test, the children here received two 54-item sets, each followed by a test involving one-two and two-three frequency pairs. Thus, this list differed substantially from that of Experiment 1 in terms of the specific items that were assigned to a given frequency level. The use of more total items and of only the one-two and two-three pairs (omitting the relatively easy one-three pairs) was done to provide greater sensitivity to possible group differences relative to Experiment 1. Results
and Discussion
Scores on the two picture sets did not differ significantly, so were combined for a single score. The analyses followed the same format as in Experiment 1. The data are summarized on the right hand side in Table 2. The pattern of results followed closely those obtained in Experiment 1. The age difference was reliable (F(1, 38) = 7.58, MS, = .816) with more errors made by the younger children. Again, none of the comparisons involving the school-identified LD, low reading, and low math groups approached significance. The results with respect to frequency difference and item type effects were as in Experiment 1 and will not be detailed further here. In short, these data confirm the conclusions implied by the data of Experiment 1 and resolve any lingering doubts regarding their validity. GENERAL DISCUSSION There was a reassuring consistency of results across the two experiments, and these results were consistent over list differences in specific items. As would have been expected from the Ghatala and Levin (1973) data, and contrary to Hasher and Zacks (1979), the accuracy of relative frequency judgments improved from 5 to 8 years of age. At age 8, however, frequency judgment accuracy was unrelated to the various patterns of school achievement that were examined. Such accuracy was considerably greater for the color + object (the usual sort of items in such tasks) than for the color only condition, but that variable did not
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interact with age or any other variable of interest. Accuracy also varied in accordance with Weber’s Law in each experiment. What are the implications of our results, together with those of Ghatala and Levin (1973), for the theoretical positions taken by Hasher and Zacks (1979)? A consideration of this question leads to an examination of possible sources of the age differences we have reported and of the apparent conflict between our results and those of Hasher and Zacks. Hasher and Zacks propose that cognitive processes vary along an “attentional-demand continuum,” with the processes involved in the encoding of event frequency lying at the low demand end of that continuum. Automatic encoding of event frequency is contingent only on minimal attention to a stimulus input, and neither conscious attention to event frequency nor the imposition of various strategies result in improved frequency judgment performance. Finally, they propose that humans are genetically prepared for the automatic processing of frequency information. As we view it, the existence of age differences, particularly over the very early school years, does not necessarily conflict with any of the above proposals by Hasher and Zacks. That is, even if our species is genetically prepared for the efficient processing of frequency information, the realization of that potential is likely to be dependent on the maturation of the neural structures involved, so that fully efficient automatic transmission of frequency information would not occur until the necessary level of maturation is reached. For some individuals, at least, that maturational level may not be attained until 7 or 8 years of age, rather than by age 5, as Hasher and Zacks concluded. This account, though speculative, would seem to require no fundamental changes in the Hasher and Zacks position, nor is it incompatible with current knowledge regarding maturational processes and genetic preparedness. It remains to account for the failure of Hasher and Zacks to detect any age differences in frequency judgment accuracy across the early elementary school years. One possibility is that our use of a greater number of subjects at each extreme of the relevant age range (32 vs 10 in the Hasher & Zacks study) provided greater sensitivity to age differences within that range. In addition, the kindergarten children in our study were slightly younger than in their study. Another major difference between the studies was our use of a relative frequency, rather than an absolute frequency, procedure during testing. However, we are unable to suggest a plausible account in those terms and, moreover, Ghatala and Levin observed an age difference with both procedures. The principal alternative to the notion of age changes in the efficiency of automatic processes is that the frequency judgment differences were due to greater attention and/or strategic processing by the older children. The conflicting results between Hasher and Zacks’ study and our own
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experiments might then be due to some difference between experiments that promoted additional attention or processing by the children in Grades 2 and 3 relative to the kindergarteners. An anonymous reviewer suggested that our inclusion of the color only condition might have had such an effect. Another suggestion was that color is relatively more salient to the younger children, and that attention to color was detrimental to performance. (Note, however, that our procedure ensured attention to object category as well as color.) If either of these explanations were correct, some significant modification of the Hasher and Zacks position would be required. It would suggest that variations in attention or strategic encoding activities, at least across some range, do influence the fidelity with frequency information as stored or retrieved. However, there are reasons to be skeptical of such an explanation. If encoding strategy differences do affect memory for event frequency, then one would expect that under the general memory instructions used by Hasher and Chromiak adults would have been substantially superior to 9-yearolds. They were not, nor were the Grade 5 children superior to the Grades 2 and 3 children in our Experiment 1. Finally, as pointed out by an anonymous reviewer, an attentional or strategic processing explanation of our age difference would suggest that the school-identified LD group in our study, a group relatively low in general intelligence, also would show a deficit in frequency judgment accuracy. No such deficit was observed in either experiment. In short, although a differential attention or differential strategy notion cannot be ruled out as an explanation for the observed age difference, the weight of the evidence seems to be against it. The fact that frequency judgment accuracy was sensitive to age, frequency level, and item type is critical for the interpretation of the null results with respect to the LD groups. Often negative results are uninterpretable because of the absence of evidence that the task was sufficiently sensitive. In the present case there appears to be no question on that point, and it seems safe to conclude that frequency processing is not deficient across a wide sampling of LD children. One of the implications of this finding concerns the possible causes of reading disability, as described in our introduction. It has been proposed by some investigators that reading disability may be a manifestation of a more general linguistic deficit (e.g., Perfetti & Goldman, 1975). Such a deficit might arise if a child were deficient in encoding information regarding the relative frequency of various linguistic units, for example, particular letter or word combinations. In fact, data have been reported that seem to indicate that poor readers know less than good readers about the frequency with which particular letters occupy particular positions in English words (Mason, 1975). raising the possibility of less effective encoding of such information by less skilled readers. Our data indicate
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that a deficit in the processing of simple event frequency information probably should be ruled out as a contributing factor in specific reading difficulties. REFERENCES Attneave, F. Psychological probability as a function of experiences frequency. Journal Experimental
Psychology,
of
1953, 46, 81-86.
Bourne, L. E., Jr., Ekstrand, B. R., Lovallo, W. R.. Kellogg, R. T., Hiew, C. C., & Yaroush, R. A. Frequency analysis of attribute identification. Journal of Experimenral Psychology: General, 1976, 105, 294-312. Ekstrand, E. R., Wallace, W. P., & Underwood, B. J. A frequency theory of verbaldiscrimination learning. Psychological Review, 1966, 73, 566-578. Estes, W. K. The cognitive side of probability learning. Psychological Review, 1976, 83, 37-64. Ghatala, E. S., & Levin, J. R. Developmental differences in frequency judgments of words and pictures. Journal of Experimental Child Psychology. 1973, 16, 495-507. Hasher, L., & Chromiak, W. The processing of frequency information: An automatic mechanism? Journal of Verbal Learning and Verbal Behavior, 1977, 16, 173-184. Hasher, L., & Zacks, R. T. Automatic and effortful processes in memory. Journal of Experimental Psychology: General, 1979, 108, 356-388. Hintzman, D. L. Apparent frequency as a function of frequency and the spacing of repetitions. Journal of Experimental Psychology, 1969, 80, 139-143. Lichtenstein, S., Slavic, P., Fischhoff, B., Layman, M., & Combs, B. Judged frequency of lethal events. Journal of Experimental Psychology: Human Learning and Memory, 1978, 4, 551-578. Mason, M. Reading ability and letter search time: Effects of orthographic structure defined by single-letter positional frequency. Journal of Experimental Psychology: General, 1975, 104, 146-166. Perfetti, C. A. & Goldman, S. R. Discourse memory and reading comprehension skill. Journal of Verbal Learning and Verbal Behavior, 1976, 14, 33-42. Shapiro, B. J. The subjective estimate of relative word frequency. Journal of Verbal Learning and Verbal Behavior, 1969, 8, 248-251. Underwood, B. J. Attributes of memory. Psychological Review, 1969, 76, 559-573. Underwood, B. J. Recognition memory. In H. H. Kendler & J. T. Spence (Eds.), Essays in neobehaviorism. New York: Appleton-Century-Crofts, 1971. Underwood, B. J. Word recognition memory and frequency information. Journal of Experimental Psychology, 1972, 94, 276-283.
REFERENCE
NOTES
1. Goldstein, D., Kosteski, D., Hasher, L., Edelman, K. M. Automatic memory processes in learning disabled children. Paper received from Lynn Hasher, Temple University, 1979. 2. Lund, A. M., & Wilson, K. P. Manuscript in preparation. RECEIVED:
July 6, 1981;
REVISED:
April 13, 1982.
OF EXPERIMENrAL
CHILD
35, 236-247 (1983)
PSYCHOLOGY
Frequency Judgment Accuracy as a Function of Age and School Achievement (Learning Disabled versus Non-Learning-Disabled) Patterns ARNOLD M. LUND Bell Laboratories JAMES W. HALL Northwestern
University
KIM P. WILSON Northwestern
University
AND MICHAEL
S. HUMPHREYS
The University of Queensland The accuracy of children’s judgments of relative situational frequency was examined in two experiments. In Experiment 1 children with normal achievement in Grades 2 and 3 were compared with such children in Grades K and 5, as well as with three groups of low-achieving children in Grades 2 and 3. These latter groups consisted of children low in reading achievement, those low in math achievement, and those identified as learning disabled. Frequency judgment accuracy increased from kindergarten to Grades 2 and 3. No other comparisons yielded significant differences. Experiment 2 confirmed both the above age difference and the absence of any frequency judgment deficiency on the part of the low-achieving groups.
Human ability to remember the frequency with which particular events have occurred has received considerable attention in recent years. Adults This research was supported by a research contract from the Bureau of Education for the Handicapped, Office of Education (US HEW OE 300 770 493) for the Chicago Institute for Learning Disabilities of the University of Illinois. We are grateful to the Evanston, Illinois school officials, teachers, and children whose cooperation made this research possible. Requests for reprints should be addressed to Arnold M. Lund, Bell Laboratories, Crawford Corner Road, Holmdel, NJ 07733. 236 0022-0965183 $3.00 CopyrIght All right\
‘Q 1983 by Academic Pres\. of reproduction in any form
Inc. reserved.
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AND
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can estimate with considerable accuracy the frequency with which particular words have occurred within a list (Hintzman, 1969), the frequency with which particular words (Shapiro, 1969), letters (Attneave, 1953), and pairs of letters (Underwood, 1971) occur in the English language, and even the frequencies of various lethal events (Lichtenstein, Slavic, Fischoff, Layman, & Combs, 1978). That ability has been implicated in recognition decisions (Underwood, 1971, 1972), verbal discrimination learning (Ekstrand, Wallace, & Underwood, 1966), probability learning (Estes, 1976), and concept formation (Bourne, Ekstrand, Lovallo, Kellogg, Hiew, & Yaroush, 1976). Hasher and Zacks (1979) have proposed an account of memory for event frequency that stresses the automaticity of processing such information. Their conclusions regarding developmental differences (or the lack thereof) are especially pertinent to the present paper: “While children become more proficient at overt and covert rehearsing, at elaborating, at imaging, at naming pictures, and at a knowledge about their own memory skills, frequency sensitivity appears to be one of those rare skills that is outside of this domain” (Hasher & Zacks, 1979, p. 370). The evidence in direct support of that conclusion derived from two experiments, both of which failed to reveal age related changes in the accuracy of frequency judgments. In one of these (Hasher & Chromiak, 1977) children in Grade 2 were compared with college students and in the second (Hasher & Zacks, 1979), children in Grades K, 1, 2, and 3 were compared. In neither case was any effort made to reduce the differences in encoding activities that ordinarily are found across this age range. It appears, then, that the absence of age differences in frequency judgment accuracy occurred despite the presence of age differences in encoding activities of the sort enumerated above. Thus, Hasher and Zacks were led to the conclusion that the processing of event frequency is independent of variations in strategic encoding activities and that humans are “genetically prepared” to efficiently process such information. Results in conflict with those of Hasher and her coworkers were obtained by Ghatala and Levin (1973, Experiment I), who in an earlier study examined both absolute and relative frequency judgments by children in Grades K, 3, and 5. (In the absolute judgment procedure, used also in the Hasher studies, test items are presented singly with the subject required to estimate the number of times the item had occurred in a study list; for the relative judgment test, pairs of study items are presented, with the subject required to indicate which items within each pair had occurred more frequently.) The Ghatala and Levin results indicated a developmental increase in the accuracy of both kinds of judgments, although the difference between Grades 3 and 5 was so slight as to suggest that a “true” developmental difference may be confined to
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the younger age period. There are, then, two published studies regarding the issue of developmental differences in frequency judgment accuracy across the very early school years, and these results are in direct conflict. Hasher and Chromiak dismissed the positive findings reported by Ghatala and Levin on the grounds of “a complex and contradictory pattern of results” and “a number of methodological problems” (Hasher & Chromiak, 1977, p. 179). However, given the relative paucity of evidence on the point, and the conflict between the relevant studies, it seems to us most reasonable to consider the matter unsettled at present. One of the two major goals of the present experiment is to provide a more definitive basis for a conclusion on the issue of developmental differences in frequency judgment accuracy across the early school years. The second main issue addressed in these experiments was the possibility of a deficiency in frequency judgment accuracy on the part of groups of children who might be characterized as learning disabled (LD). There were three groups of such children. One group consisted of children formally identified by school personnel as learning disabled. The second group was not formally identified as LD but displayed a specific deficiency in reading achievement. The third group also was not formally identified as LD but displayed low achievement specific to mathematics. Frequency judgment accuracy appears to be one of the few tasks that has received little use in the study of LD children. The only such study we have found is an unpublished one by Goldstein, Kosteski, Hasher. and Edelman (Note 1) in which no difference was found in the ability to discriminate among items varying in situational frequency. As with so many studies of LD children, however, no effort was made to isolate groups in which there was a commonality of specific achievement problems (e.g., reading difficulty). Such distinctions are desirable, because it seems quite likely that cognitive factors underlying reading difficulties may differ substantially from those that produce difficulties in mathematics, for example. To illustrate, and especially pertinent to the present experiments, it has been proposed that children with reading disabilities may suffer from inadequate knowledge of information about the frequency with which particular letters and combinations of letters occupy various positions in English words (Mason, 1975). One possible cause of such an information deficiency would be a deficiency in the processing of frequency information. A distinctive feature of our experiments was in the nature of the items to be judged. In previous studies involving very young children the procedure was to use pictures of common objects, with some objects occurring once, some twice, etc. Thus, for example, a ball might be seen once and a house twice, with the subject subsequently asked to judge which of the two had occurred more often. In the present experiments, in addition to such pairs (e.g., a white house and a yellow ball), there
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also were items that differed only in color (following a procedure introduced by Lund & Wilson, Note 2). For example, a brown kite appeared twice and a white kite once. Accuracy of relative frequency judgments to this pair would require a frequency code that is separate for two versions (colors) of the same semantic category (kite). One might expect the latter decision to be more difficult than in the case in which items differed in both category and color (white house vs yellow ball). Therefore, it might be more sensitive to the individual difference variables of concern here than were past experiments. Experiment 1 examined frequency judgment accuracy of children in Grades K, 2, 3, and 5. In addition, the three low-achievement subgroups described above were compared to the normal achievement children in Grades 2 and 3. Experiment 2 was a somewhat modified replication of Experiment 1. A relative judgment procedure was used throughout, in contrast to the absolute judgment procedure used by Hasher and Chromiak (1977) and Hasher and Zacks (1979). Although there was no a priori reason to expect that this procedure would be more sensitive to age differences, it remained a possibility worth examining. EXPERIMENT
1
Method Subjects. Six groups of public elementary school children (total N = 146) participated in the study. Four groups were drawn from Grades 2 and 3. Achievement and general intelligence test data along with other descriptive information for these groups are summarized in Table 1. One of these groups consisted of 28 children identified through school procedures as learning disabled (LD). The school district’s formal guidelines for such identification were consistent with those in common use, specifying the presence of a discrepancy between academic aptitude and academic achievement for which the probable cause is some specific cognitive processing deficit. In fact, however, in practice there is considerable ambiguity and subjectivity in the identification procedures, and one cannot be entirely certain just what population is being sampled in any given instance. Partly for that reason, and partly because such an LD group can be expected to be highly heterogeneous in the nature of their academic difficulties, both a low reading and a low mathematics (math) group were identified and included in the study. Although LD children often are assumed to be of normal intelligence but with a specific area of achievement difficulty, our data indicated otherwise for most of these school-identified LD children, Instead, most of these children were low in general intelligence as well as in achievement in both reading and math, with somewhat lower achievement in reading. The low reading group consisted of 27 children selected by virtue of reading scores at least two stanines below math achievement scores, and
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LUND ET AL. TABLE CHARACTERISTICS
Measure N CA (years) M
SD Sex (M/F) Brief cog” M
SD
OF GRADES
1
2 AND
3 SAMPLES
IN EXPERIMENT
1
Normal achievers
School learning disabled
Low reading
32
28
21
12
8.12
8.61
8.14
.66
.73
1804
.76 2018
7.94 .59 418
106.03 14.16
85.35 11.22
103.76
11.41
12.36
106 13.77
80 10.67
90 9.48
109 12.62
108 13.58
86
112
11.09
11.47
89 8.88
1819
Low math
102.83
Rdng Ach”
M SD Math Ach
M SD
Note. Brief cog, Brief Cognitive scales of the Woodcock-Johnson; achievement; Math ach, mathematics achievement. ’ Population M = 100, SD = 15.
Rdng ach, reading
where general intelligence scores were closer to the math than to the reading scores. The 12 low math children were at least two stanines lower in math than in reading, with general intelligence scores roughly in line with reading scores. The reading-math discrepancies were based on two sets of achievement test scores, one from the California Achievement Test and one from the Woodcock-Johnson Psycho-Educational Battery. Only the Woodcock-Johnson scores are shown in Table 1. The general intelligence estimates were derived from the Brief Cognitive scale of the Woodcock-Johnson. Four of the low reading children and two of the low math children whom we identified also were among the 28 children whom the schools identified as LD, producing some overlapping membership among these three groups. The fourth group, the normal achievers, consisted of 32 children chosen unsystematically except to exclude children with large reading-math discrepancies and those with general intelligence below the normal range. The 32 kindergarten (chronological age (CA) mean = 5.61, SD = .33) and 21 Grade 5 (CA mean = 10.42, SD = .44) children were selected randomly from classrooms at that level except to exclude children with obvious (by teacher judgments) handicaps. There were 13 boys and 19 girls in the kindergarten sample and 15 boys and 6 girls at Grade 5. Achievement and intelligence test data were not available for the kindergarten and Grade 5 children. Design and material. The experiment consisted of two distinct aspects, the first involving comparisons of frequency judgment accuracy among
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the normal achievers at the three age levels, and the second consisting of comparisons among the four achievement groups at Grades 2 and 3. The normal achieving children in Grades 2 and 3 participated in both sets of comparisons. Following a presentation of a series of pictures for which he produced labels (the study phases), each child was presented a set of test pairs, the pictures in each pair having occurred differing numbers of times during study presentation. A relative frequency judgment was required for each pair. Pair frequencies of one versus two, two versus three, and one versus three occurred equally often during testing. Within each pair frequency level half the picture pairs differed both in the objects’ semantic categories and in their color, for example, a white house and a yellow ball. These are termed the object and color items. The remaining half, the color only items, consisted of pairs in which the object was the same except for a difference in color, for example, a brown kite and a white kite. Two forms of the study list were constructed, each consisting of 78 pictures and each following the same format. Each set contained 12 pictures that appeared once, 12 that appeared twice, and 12 that appeared three times, plus three buffer pictures at the beginning and three at the end of the set. Within each subset of pictures at a given frequency level, six were of the object-color and six of the color only type. The pictures were line drawings of common objects colored red, white, brown, blue, yellow, or black. Each color occurred equally often at each frequency level and as the correct item in the test pairs. Inappropriate color-object pairings (e.g., a red cat) were not used. With these restrictions items were assigned randomly to frequency levels. Item order was random except that the same object never occurred on successive cards. Test pairs were evenly divided among the frequency combinations one-two, two-three, and one-three, half of each being object + color and half color only pairs. Thus, there were 3 one-two object + color pairs, 3 one-two color only pairs, 3 two-three object + color pairs, and so on, Order of test pairs was random. Procedure. To enhance motivation and attention, especially among the younger children, a game format was used in which a cartoon figure of a clown was displayed. The clown’s nose was prominent and the child was urged to make it grow even more. This could be done by correctly naming aloud the object and its color in each picture during the study period and by a correct relative frequency judgment during the test phase. In each case the experimenter intermittently placed a red chip on the nose of the clown. Each session began with an explanation of the “game,” followed by a brief test to ensure that the child understood the rules and could identify the colors used. Following a brief practice list the study list was presented at approximately 4 set per picture, with hints given on those rare occasions
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on which the child displayed hesitation in identifying an object or its color. The final forced-choice relative frequency judgment test was unpaced: The child simply was asked to indicate which of the two verbally described pictures had appeared more often during the study period. Results and Discussion Performance means are shown on the left in Table 2 collapsed over list form and frequency level. Four unequal-number ANOVAs were performed. In the first of these, four variables entered the analysis: groups (normal achievers in Grades K, 2, 3, and 5), frequency (one-two, two-three, and one-three), item type (object + color vs color only), and list form. In the three remaining analyses each of the three lowachievement groups was compared in turn with the normal achievers at Grades 2 and 3, and again the variables of frequency, item type, and list form were entered into the analyses. The low-achievement groups were treated separately here because of the marked differences in the operational criteria by which they were defined. Since there was no systematic effect of list form, and since list form was of no inherent interest, it will not be considered further. For all analyses significance was accepted at the .05 level. The results pertaining to age differences will be considered first. As may be seen in Table 2, kindergartners were less accurate overall than were the older two groups, the latter displaying nearly equal performance, with a slight edge to the Grades 2 and 3 children. This was confirmed by a significant effect of age, F(2, 79) = 7.61, MS, = 736. As expected, the color only items were more difficult than the object TABLE 2 MEAN NUMBER OF ERRORS~IN EXPERIMENTS 1 AND 2 Experiment
1
Experiment 2
Group achievement
Grade
Object + color
Color only
Object + color
Color only
Normal Normal Normal School LD Low rd Low math
K 2, 3b 5 2, 3b 2, 3b 2, 3b
.68 .33 .35 s2 .33 .58
1.33 1.03 1.13 1.01 1.21 1.06
1.63 1.08 1.33 1.08 1.10
2.08 1.83 1.95 2.00 1.75
Note. LD, learning disabled; rd, reading. ” The means within cells are based on a total of three possible errors per subject in Experiment 1 and on 6 per subject in Experiment 2. b In Experiment 1 these groups consisted of children in Grades 2 and 3; in Experiment 2 they comprised children in Grade 3 only.
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+ color items, F(1, 78) = 110.72, MS, = .507. (Both of these patterns of results were found for each form of the list.) This was consistent with the assumption that an additional encoding process, the formation of an association between color and object name, is required for the successful discrimination of the color only test items. The main effect of frequency levels also was reliable, F(2, 158) = 7.68, MS, = .425. Here, in accord with Weber’s Law, it was most difficult to discriminate between the two-three items and least difficult for the one-three items. The above results were consistent with those reported earlier by Ghatala and Levin (1973), and contrary to those of Hasher and Zacks (1979) in their indication of an age difference in frequency judgments across the first few school years. In finding no difference between the children in Grades 2, 3, and 5 they are consistent with the Hasher and Chromiak (1977) findings. We had expected that the color only items might be more sensitive to age differences, but in fact the age difference reported above did not vary with item type. The remaining three analyses involved a comparison of the normal Grade 2 and 3 children with each of the low-achievement groups in turn. The results are straightforward; although the low math group in particular was somewhat less accurate than the normal achievers, none of these comparisons showed a reliable group difference. Again in these analyses the effects of frequency difference were significant and the differences followed the same pattern as reported for the developmental comparison. The F’s(2, 112) ranged from 6.64 to 8.12 for the frequency variable, MS, from .375 to .398. For the item type variable the values of F( 1, 56) ranged from 49.89 to 100.38, and the MS, from .362 to .474. In Experiment 2 a modified replication of Experiment 1 was performed. This was done for two reasons. First, age differences in frequency judgment accuracy had been in serious question. In fact, the absence of such differences played a prominent role in arguments by Hasher & Zacks (1979) for the automaticity of event frequency processing. It seemed prudent, therefore, to be quite certain of our results. Second, there was a hint of a possible difference between the normal achievers and the low math children (see Table 2) that appeared to warrant additional investigation. EXPERIMENT
2
Method Subject and design. In Experiment 2 the developmental comparison was confined to two age-grade levels (Grades K and 3). Again, comparisons also were made between normal achievers and school-identified LD, low reading, and low math groups, this time at Grade 3. Other than the grade level difference, these four groups were defined as in Experiment 1; their relative achievement and intelligence levels differed only
244
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slightly from the previous groups. Of the 88 children participating in Experiment 2, 20 were school-identified LD, eighteen were low reading, 10 were low math, and 20 each for the normal Grade 3 and the kindergarten groups. The design was the same as for Experiment 1 except that only one versus two and two versus three frequency pairs were presented during the test phase and only a single form of the picture set was used. Materials and procedure. Each child received, in succession, two study-test picture sets, each consisting of 24 different pictures plus six buffers. Of the 24 target pictures, 6 appeared once, 12 twice, and 6 three times. The procedure was identical to that in the first experiment except that instead of receiving one 78-item study list followed by a test, the children here received two 54-item sets, each followed by a test involving one-two and two-three frequency pairs. Thus, this list differed substantially from that of Experiment 1 in terms of the specific items that were assigned to a given frequency level. The use of more total items and of only the one-two and two-three pairs (omitting the relatively easy one-three pairs) was done to provide greater sensitivity to possible group differences relative to Experiment 1. Results
and Discussion
Scores on the two picture sets did not differ significantly, so were combined for a single score. The analyses followed the same format as in Experiment 1. The data are summarized on the right hand side in Table 2. The pattern of results followed closely those obtained in Experiment 1. The age difference was reliable (F(1, 38) = 7.58, MS, = .816) with more errors made by the younger children. Again, none of the comparisons involving the school-identified LD, low reading, and low math groups approached significance. The results with respect to frequency difference and item type effects were as in Experiment 1 and will not be detailed further here. In short, these data confirm the conclusions implied by the data of Experiment 1 and resolve any lingering doubts regarding their validity. GENERAL DISCUSSION There was a reassuring consistency of results across the two experiments, and these results were consistent over list differences in specific items. As would have been expected from the Ghatala and Levin (1973) data, and contrary to Hasher and Zacks (1979), the accuracy of relative frequency judgments improved from 5 to 8 years of age. At age 8, however, frequency judgment accuracy was unrelated to the various patterns of school achievement that were examined. Such accuracy was considerably greater for the color + object (the usual sort of items in such tasks) than for the color only condition, but that variable did not
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interact with age or any other variable of interest. Accuracy also varied in accordance with Weber’s Law in each experiment. What are the implications of our results, together with those of Ghatala and Levin (1973), for the theoretical positions taken by Hasher and Zacks (1979)? A consideration of this question leads to an examination of possible sources of the age differences we have reported and of the apparent conflict between our results and those of Hasher and Zacks. Hasher and Zacks propose that cognitive processes vary along an “attentional-demand continuum,” with the processes involved in the encoding of event frequency lying at the low demand end of that continuum. Automatic encoding of event frequency is contingent only on minimal attention to a stimulus input, and neither conscious attention to event frequency nor the imposition of various strategies result in improved frequency judgment performance. Finally, they propose that humans are genetically prepared for the automatic processing of frequency information. As we view it, the existence of age differences, particularly over the very early school years, does not necessarily conflict with any of the above proposals by Hasher and Zacks. That is, even if our species is genetically prepared for the efficient processing of frequency information, the realization of that potential is likely to be dependent on the maturation of the neural structures involved, so that fully efficient automatic transmission of frequency information would not occur until the necessary level of maturation is reached. For some individuals, at least, that maturational level may not be attained until 7 or 8 years of age, rather than by age 5, as Hasher and Zacks concluded. This account, though speculative, would seem to require no fundamental changes in the Hasher and Zacks position, nor is it incompatible with current knowledge regarding maturational processes and genetic preparedness. It remains to account for the failure of Hasher and Zacks to detect any age differences in frequency judgment accuracy across the early elementary school years. One possibility is that our use of a greater number of subjects at each extreme of the relevant age range (32 vs 10 in the Hasher & Zacks study) provided greater sensitivity to age differences within that range. In addition, the kindergarten children in our study were slightly younger than in their study. Another major difference between the studies was our use of a relative frequency, rather than an absolute frequency, procedure during testing. However, we are unable to suggest a plausible account in those terms and, moreover, Ghatala and Levin observed an age difference with both procedures. The principal alternative to the notion of age changes in the efficiency of automatic processes is that the frequency judgment differences were due to greater attention and/or strategic processing by the older children. The conflicting results between Hasher and Zacks’ study and our own
246
LUNDETAL.
experiments might then be due to some difference between experiments that promoted additional attention or processing by the children in Grades 2 and 3 relative to the kindergarteners. An anonymous reviewer suggested that our inclusion of the color only condition might have had such an effect. Another suggestion was that color is relatively more salient to the younger children, and that attention to color was detrimental to performance. (Note, however, that our procedure ensured attention to object category as well as color.) If either of these explanations were correct, some significant modification of the Hasher and Zacks position would be required. It would suggest that variations in attention or strategic encoding activities, at least across some range, do influence the fidelity with frequency information as stored or retrieved. However, there are reasons to be skeptical of such an explanation. If encoding strategy differences do affect memory for event frequency, then one would expect that under the general memory instructions used by Hasher and Chromiak adults would have been substantially superior to 9-yearolds. They were not, nor were the Grade 5 children superior to the Grades 2 and 3 children in our Experiment 1. Finally, as pointed out by an anonymous reviewer, an attentional or strategic processing explanation of our age difference would suggest that the school-identified LD group in our study, a group relatively low in general intelligence, also would show a deficit in frequency judgment accuracy. No such deficit was observed in either experiment. In short, although a differential attention or differential strategy notion cannot be ruled out as an explanation for the observed age difference, the weight of the evidence seems to be against it. The fact that frequency judgment accuracy was sensitive to age, frequency level, and item type is critical for the interpretation of the null results with respect to the LD groups. Often negative results are uninterpretable because of the absence of evidence that the task was sufficiently sensitive. In the present case there appears to be no question on that point, and it seems safe to conclude that frequency processing is not deficient across a wide sampling of LD children. One of the implications of this finding concerns the possible causes of reading disability, as described in our introduction. It has been proposed by some investigators that reading disability may be a manifestation of a more general linguistic deficit (e.g., Perfetti & Goldman, 1975). Such a deficit might arise if a child were deficient in encoding information regarding the relative frequency of various linguistic units, for example, particular letter or word combinations. In fact, data have been reported that seem to indicate that poor readers know less than good readers about the frequency with which particular letters occupy particular positions in English words (Mason, 1975). raising the possibility of less effective encoding of such information by less skilled readers. Our data indicate
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that a deficit in the processing of simple event frequency information probably should be ruled out as a contributing factor in specific reading difficulties. REFERENCES Attneave, F. Psychological probability as a function of experiences frequency. Journal Experimental
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Bourne, L. E., Jr., Ekstrand, B. R., Lovallo, W. R.. Kellogg, R. T., Hiew, C. C., & Yaroush, R. A. Frequency analysis of attribute identification. Journal of Experimenral Psychology: General, 1976, 105, 294-312. Ekstrand, E. R., Wallace, W. P., & Underwood, B. J. A frequency theory of verbaldiscrimination learning. Psychological Review, 1966, 73, 566-578. Estes, W. K. The cognitive side of probability learning. Psychological Review, 1976, 83, 37-64. Ghatala, E. S., & Levin, J. R. Developmental differences in frequency judgments of words and pictures. Journal of Experimental Child Psychology. 1973, 16, 495-507. Hasher, L., & Chromiak, W. The processing of frequency information: An automatic mechanism? Journal of Verbal Learning and Verbal Behavior, 1977, 16, 173-184. Hasher, L., & Zacks, R. T. Automatic and effortful processes in memory. Journal of Experimental Psychology: General, 1979, 108, 356-388. Hintzman, D. L. Apparent frequency as a function of frequency and the spacing of repetitions. Journal of Experimental Psychology, 1969, 80, 139-143. Lichtenstein, S., Slavic, P., Fischhoff, B., Layman, M., & Combs, B. Judged frequency of lethal events. Journal of Experimental Psychology: Human Learning and Memory, 1978, 4, 551-578. Mason, M. Reading ability and letter search time: Effects of orthographic structure defined by single-letter positional frequency. Journal of Experimental Psychology: General, 1975, 104, 146-166. Perfetti, C. A. & Goldman, S. R. Discourse memory and reading comprehension skill. Journal of Verbal Learning and Verbal Behavior, 1976, 14, 33-42. Shapiro, B. J. The subjective estimate of relative word frequency. Journal of Verbal Learning and Verbal Behavior, 1969, 8, 248-251. Underwood, B. J. Attributes of memory. Psychological Review, 1969, 76, 559-573. Underwood, B. J. Recognition memory. In H. H. Kendler & J. T. Spence (Eds.), Essays in neobehaviorism. New York: Appleton-Century-Crofts, 1971. Underwood, B. J. Word recognition memory and frequency information. Journal of Experimental Psychology, 1972, 94, 276-283.
REFERENCE
NOTES
1. Goldstein, D., Kosteski, D., Hasher, L., Edelman, K. M. Automatic memory processes in learning disabled children. Paper received from Lynn Hasher, Temple University, 1979. 2. Lund, A. M., & Wilson, K. P. Manuscript in preparation. RECEIVED:
July 6, 1981;
REVISED:
April 13, 1982.