Relationship Between Single Word Decoding and Reading ...

Journal of Educational Psychology 1976, Vol. 67, No. 4, 461-469

Relationship Between Single Word Decoding and Reading Comprehension Skill Charles A. Perfetti and Thomas Hogaboam Learning Research and Development Center and Department of Psychology, University of Pittsburgh Children classified as skilled and less skilled in reading comprehension differed in vocalization latencies to single printed words. Overall, vocalization latencies were shorter for the skilled group than the loss skilled group and there was an interaction between word type and comprehension skill. The comprehension groups showed large vocalization latency differences for pseudowords and for low frequency English words, but smaller differences for high frequency English words. Knowledge of word meanings may be a less significant factor in vocalization latency for the skilled group than for the unskilled group. It is suggested that at least some unskilled comprehenders may have failed to develop automatic decoding skills and that this failure may lead to diminished comprehension skills sharing a common processing capacity with nonautomatic decoding.

The conceptualization of reading as composed of separable components allows more than one view on the relationship between the components. The cognitive components of reading can be considered as separable and independent or as separable and interdependent. As Guthrie (1973) has argued, the more tenable view for at least some components is that they are interdependent and mutually facilitative. In the case of decoding and comprehension, there are similar possibilities of independence and interdependence. For at least some indicators of decoding, it seems clear that decoding is not sufficient for comprehension (Cromer, 1970; Wiener & Cromer, 1967). However, it does not follow that decoding and comprehension are independent. Rather, reading comprehension depends on the availability of highly developed skills, including the ability to convert print into the language code. The required conceptualization of the

reading process is one that takes account of the fact that all basic processes carried out in an integrated behavior such as reading not only interact with each other but also must share a limited capacity mechanism, at least in part. A mechanism which is heavily demanded by one process essentially becomes less available for other processes. Thus, if a reader requires considerable processing capacity to decode a single word, his processing capacity is less available for higher order integrated processes—for example, memory for the just previously coded word may suffer, memory for the preceding phrase may decrease, and the subject's ability to "predict" what he is yet to encounter on the printed page may diminish. There is evidence that skilled comprehenders have basic word skills that are superior to those of unskilled comprehenders. For example, Katz and Wicklund (1971) found differences between good and poor comprehenders for a word-scanning task in This research was supported by the Learning which children had to decide whether a Research and Development Center, which is supported in part by funds from the National Insti- target string of printed words contained a previously presented key word. Good comtute of Education. The assistance of Susan Goldman with various prehenders were faster at this task than stages of the research is acknowledged. were poor comprehenders. However, in a Requests for reprints should be sent to Charles similar scanning task involving letters, Katz A. Perfetti, Learning Research and Development Center, 3939 O'Hara Street, Pittsburgh, Pennsyl- and Wicklund (1972) found no difference between reader groups. Thus, at least for vania 15260. 461

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visual scanning, it appears that less skilled readers may have different word recognition skills but comparable letter recognition skills. Katz and Wicklund (1972) in fact provide arguments in support of the notion that a basic retrieval process difference, rather than word recognition difference, underlies the difference in word scan rate. They suggest that retrieval of a name code is the essential component of the word scan task and good comprehcndcrs have more facility with retrieving name codes than do poor readers. There is evidence directly implicating word decoding differences between good and poor readers in a study by Calfee, Venezky, and Chapman (Note 1), who found that good readers produce more correct pronunciations of artificial words that have predictable orthographic correspondences (e.g., initial c corresponds to /k/ rather than /s/). Also, a recent study by Coomber and Hogie (Note 2) seems to implicate decoding factors in reading achievement. Such studies may be important in identifying basic word level differences related to comprehension, although the nature of the differences has not yet been identified. In the experiment reported here, we focus on word decoding and production. By decoding we mean the transfer of the written code to the language code. By production we mean the vocalization of the decoded unit. In our task a reader was to observe a printed word projected on a screen in isolation and to say the word as quickly as possible. Thus, both decoding and production arc components of the subject's task. However, "decoding," in this sense, docs not necessarily refer to a unitary process. It involves, in some cases, mainly word recognition and, in other cases, mainly code breaking, while often both are involved. There is a related but conceptually distinct complication, namely whether the reader has a meaning for the word once it is decoded. These distinctions are related in the sense that highly available word meanings may be associated with word recognition and unknown word meanings may be typically associated with code breaking.

These decoding components are important and deserving of careful study as component processes. It is possible that skilled and unskilled readers differ on one or the other of these components. It is likely, for example, that children who are skilled comprehenders know more word meanings than children who are less skilled. The question thus becomes twofold: How do skilled and less skilled comprehenders compare on decoding of words for which they know the meaning and how do they compare on the decoding of words for which they do not know the meaning? Differences on both of these are compatible with the conceptualization that basic word skills are involved in higher order comprehension processes. One could, therefore, expect general differences between skilled and less skilled comprehenders on both types of words. On the other hand, the main difference could lie with words for which the meanings are not known to the reader. This would implicate, in a sense, a basic code-breaking skill. It is a skill also which bears a less obvious relation to comprehension. Certainly the notion of comprehension docs include the identification of word meanings, whereas comprehension is not often thought of as being closely related to code breaking. Since the measure in the present experiment is word vocalization, some note should be made of the variables that affect it. For example, it is known that the number of syllables in a word is positively related to the reaction time for overt vocalization (Eriksen, Pollack, & Montague, 1970). Klapp, Anderson, and Berrian (1973) have shown that the syllable effect is not dependent on the pronunciation of the words. That is, vocalization time is related to decoding and response preparation and not just to the requirements of vocalization. The issue in the adult research is whether implicit speech mediates recognition of single words when that recognition is measured by a production task. Whether implicit speech is involved is not critical for the present experiment; however, Klapp et al. (1973) have argued that the vocalization experiments do not provide evidence that implicit speech is necessary for word recognition. The present experiment thus is conceived

DECODING AND READING

to provide a direct test of the hypothesis that children who are distinguished as being skilled and less skilled comprehenders, as measured by a standardized reading achievement test of comprehension, are distinguished by latency of vocalization in a word identification task. METHOD Design The independent variables of the study were word type and reader group, and the study was designed to permit two overlapping analyses. One analysis eould be performed on a set of words common to all subjects within a grade. The second analysis would permit a 2 (Comprehension Level) X 3 (Word Frequency) factorial design with two replications, a third-grade population and fifthgrade population. This analysis involves a variable set of words which excluded for each subject words inaccurately produced and words missed on a vocabulary test. Word frequency was a within-subjects variable and was represented by high and low frequency words plus a class of pseudowords. Materials were designed to permit ad hoc comparisons on selected word subsets. One comparison of major importance is between the words whose meaning is known to a given subject and words with unknown meaning.

COMPREHENSION

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had printed frequencies fewer than 44 per million. As with the third-grade words, syllable length and printed frequency did not vary independently. The third class of words (Pseudowords) contained 10 one-syllable pronounceable nonwords for the third grade and 7 of these 10 for the fifth grade. The purpose of only 7 nonwords for the fifth grade was to match the number of one-syllable words from the Common Sot. The selection of words permitted an analysis to be made on the Common Set, as a class of high frequency familiar meaning terms. A second analysis was to be made on the three-level frequency variable. For each grade, a median split of real words on the basis of frequency defines high and low frequency words regardless of whether they are from the Common Sot or the Variable Set. The third level of the frequency variable consisted of pseudowords. Procedure

Each word was presented in lowercase elite type on a 2 X 2 in (5.08 X 5.08 cm) slide by means of a Kodak Carrousel projector equipped with a solenoid-operated shutter. The slides were projected on a rearview projection scroen. Opening the shutter started a digital timer (Hunter Klockcounter) which was stopped by a voice-operated relay at the subject's initial vocalization. The voice-operated relay also closed the shutter so that the word could not be seen after initial vocalization. Subjects were told that they were to say each Material word quickly, but that they should not attempt to For each grade, 40 experimental words were say the word until they "knew what it was." It selected along with 18 practice words. These ex- was explained that the word would disappear as perimental words were classified as high frequency, soon as they started to say the word and that this low frequency, and pseudowords. In order to would make it difficult to "sound out" the word. allow direct comparisons on words that every If the subjects did not respond appropriately durchild knew and on words that were not known by ing the warm-up slides, the instructions were reany given child, the following selection procedures peated. Following the presentation of warm-up slides, were followed: The first 10 words from the oral reading list of the test slides were presented in a random order. Wide Range Achievement Test were designated as In all cases the experimenter would say "ready" the Common Set. Thus, the Common Set contained just prior to opening the shutter for each word. If high frequency words known to all children in the no response occurred after 15 seconds had elapsed, experiment. These words were common also in the the shutter was closed and the 15-second latency sense that they provided a pool of words for direct was recorded, otherwise the actual latency was recorded and the projector advanced to the next comparison between comprehension groups. A second set of words (Variable Set) was chosen slide. In addition, the experimenter attempted to so that any given child would know the meaning determine whether the word had been correctly of some of the sot but not necessarily all. For the produced. In most cases this was straightforward third grade, the Variable Set contained 10 one- but if the experimenter could not easily and quickly syllable and 10 two-syllable words from the vo- determine whether the word had been "missed," cabulary subtest of the alternate form of the ele- the subject was asked to repeat the word. If the mentary level Metropolitan Achievement Test. word was then correctly produced, the original The third-grade Variable Set had printed frequen- response was counted as correct, otherwise it was cies ranging from 1 to 597 per million (Carroll, recorded as incorrect. Immediately following the completion of the Davics, & Hichman, 1971). For the fifth grade, the Variable Set contained 21 words from the vocabu- test slides, a multiple-choice vocabulary test was lary subtest of the alternate form Metropolitan administered. The test items were the Variable Achievement Test, 7 each of one-, two-, and three- Word Set and provided information concerning syllable words. The Variable Set for the fifth grade word knowledge that could be used in the analyses.

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Subjects Subjects wore 64 students from a Pittsburgh parochial school in a predominantly white, working-class neighborhood. The 32 third-grade subjects consisted of 15 boys, 8 in the skilled group and 7 in the less skilled group, and 17 girls, 8 in the skilled group and 9 in the less skilled group. The fifth grade consisted of 6 boys and 10 girls in each of the two skill groups. Subjects were assigned to comprehension groups on the basis of their scores on the reading subtest of the Metropolitan Achievement Tost, administered by research staff. After students in the highest and lowest stanines were excluded, the highest 16 and lowest 16 in each grade were assigned to the skilled and less skilled groups, respectively. The resultant percentile ranks were as follows: third grade, less skilled 4-26 and skilled 76-91; fifth grade, less skilled 15-30 and skilled 60-95. Subjects could not be precisely matched on TQ, but the two comprehension groups represented overlapping ranges in scores on the Otis-Lennon Mental Ability Test given by the school. The mean scores were 99 and 112 for the third grade and 107 and 120 for the fifth grade, with the skilled groups having higher mean IQs in each grade. All subjects were tested individually in a session lasting about 20 minutes.

RESULTS Two overlapping analyses comprise the main results of the experiment. First, an analysis of variance for vocalization latencies for the Common Set only was carried out to provide some direct comparison of the two comprehension groups within each grade. The second analysis examined mean vocalization latencies for pseudowords and high and low frequency real words by means of a 3 X 2 repeated measures analysis of variance. For real words, only those words for which the child knew the meaning as measured by the vocabulary test were included. In effect, this meant that the high frequency in the second analysis consisted TABLE 1 MEAN VOCALIZATION LATENCIES FOB COMMON WOKDS (in milliseconds) Comprehension level Group

Grade 3 (n = 16) Grade 5 (n = 16)

Skilled

Less skilled

916 949

1,180 1,298

largely of words from the Common Set from the first analysis plus a few high frequency words from the Variable Set, whereas the low frequency words came largely from the Variable Set. For all latency analyses, words which were not produced correctly were not included. For all latency data, analyses were performed both on raw data and on log-transformed latencies. Since they produced identical patterns of results, only the raw score analyses are reported below. Common Words Table 1 shows the mean vocalization latencies for the set of 10 common words for the two grades and the two comprehension groups. An F' statistic was computed (where appropriate) to allow the interpretation that both words and subjects represent random effects. For the third grade there were significant effects of comprehension level, F'(l,29) = 10.65, p < .01, and words, F(9,270) = 4.86, p < .01. Subjects within a comprehension group also differed significantly from each other, F (30,270) = 19.06, p < .01. No interactions approached significance, with all F's less than 1. For the fifth grade the two comprehension groups also differed significantly, F'(l,20) = 5.90, p < .001. No other factors were significant. In all cases the direction of the differences indicated that skilled readers had shorter vocalization latencies than the less skilled. This was true even though the words were all common words which were almost all produced correctly by both skilled and less skilled readers. All-Word Analysis The all-word analysis included all words that were both produced correctly and whose meaning was known for a given subject. This means no two subjects necessarily provided data on exactly the same set of words, although for high frequency words they tended to be nearly the same for all subjects, since almost all of the meanings were known to all subjects. For each grade separately, the Common Set and the Variable Set of words were pooled and divided into high and low frequency groups on the

DECODING AND READING COMPREHENSION

basis of a median split. Then those words that were missed on the vocabulary test were eliminated, as were words inaccurately produced. Common words were always categorized as having known meanings. The percentage of words classified as known and correctly produced can be seen in Table 2. For each subject, an average vocalization latency for each word type—high frequency, low frequency, and pseudowords—was computed and a 3 X 2 repeated measures variance analysis was carried out for each grade. For each grade, there were 16 skilled comprehenders and 14 less skilled comprehenders who had data usable for this analysis. In each grade, 2 subjects from the less skilled group were discarded for this analysis because they failed to meet the word knowledge or word production criterion for a particular word type. The results of the third-grade analysis showed a significant effect of comprehension level, F(l,28) = 6.90, p < .05, and word type, F(2,56) = 13.45, p < .01. The interaction between word type and comprehension level was marginally significant, F(2,56) = 2.90, p = .06. For the fifth grade, there was a significant effect of comprehension level, F(l,28) = 12.64, p < .01, and word type, F(2,56) = 13.54, p < .01. The interaction between word type and comprehension level was also significant, F(2,5Q) = 4.54, p < .05. The data for all words can be seen in Figure 1. As supported by the variance analyses, vocalization latencies decreased with increasing word frequency for both comprehension levels for both grades. The interaction between frequency and comprehension skill was significant for the fifth grade and approached significance for the third grade. For the fifth grade, simple effects tests were made between the two comprehension levels for each of three word types. The difference between the groups was highly significant only for pseudowords and for low frequency words. For high frequency words, the simple effects F was less than 1. Thus for the fifth grade, the skilled and less skilled comprehenders showed little difference on mean vocalization latency for high frequency words.

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TABLE 2 PROPORTION OF ALL REAL WOHDS ACCORDING TO PRODUCTION ACCURACY AND VOCABULARY KNOWLEDGE

Group

Correctly produced

Incorrectly produced

Known Unknown Known Unknown

Grade 3 Skilled Less skilled Grade 5 Skilled Less skilled

.84 .59

.10 .18

.03 .07

.02 .15

.69 .46

.21 .20

.04 .08

.04 .24

Note. Cell entries are proportions of all words falling into one of four categories. The rows sum to 1.0, except for a few unclassifiable responses and rounding.

For the third grade, two a posteriori contrasts were tested for the significant word type effect. The real words versus pseudowords contrast was significant, F(l,56) = 14.20, p < .05, as was the high frequency versus low frequency contrast, F(l,56) '= 12.70, p < .05. While the Word Type X Comprehension Level interaction was of marginal significance (p = .06), it is in the same direction as the significant fifth-grade interaction. The two comprehension groups showed greater difference for low frequency and pseudowords than for high frequency words. Known Versus Unknown Words A result of some interest concerns a comparison of words whose meaning was known to the child with words that were unknown. It was possible to divide the Variable Set of words into "known" and "unknown" on the basis of the recognition vocabulary test. Since a significant number of the skilled readers knew all of the high frequency words, comparisons were only possible for low frequency words where a mean score for "known" and "unknown" words could be calculated for each subject. Table 3 shows the overall mean vocalization latency for all groups of subjects for known and unknown words. The mean vocalization latency for pseudowords is also presented as a comparison. Since the Variable

CHARLES A. PERFETTI AND THOMAS HOGABOAM

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LOW COMPREHENSION GROUPS