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The Wechsler Preschool Primary Scale of Intelligence-Revised: A Comprehensive Review
Psychological testing looking at cognitive abilities across different individuals of varying age groups has been an ever-increasing field of study in Psychology. More specifically, the development of assessments of children’s cognitive abilities continues to be an area of interest because of its involvement in early childhood evaluations and educational implications.
David Wechsler (1896-1981), an eminent American psychologist contributed many important measures of intelligence through his development of various psychological tests. Among them were the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) in 1967. During this period, the U.S. government began to create special programs like Head Start whose focus was on the intellectual and developmental needs of preschool and elementary aged children in public schools. In response, the WPPSI was created in order to provide the government with an adequate way of assessing programs like Head Start. Currently, the WPPSI has been revised twice and the most recent form of the test is referred to as the WPPSI-III. For the purposes of this paper, all analyses and information presented will address the second version of the popular test, the WPPSI-Revised (WPPSI-R).
The WPPSI-R, like the original WPPSI, was revised and developed to serve as a measure of cognitive functioning of children. Essentially, this particular test is a measure of intelligence, other wise referred to as a child’s g. Published twenty-two years after the original in1989, the WPPSI measures verbal, nonverbal, and general intelligence in children the age range of 3 years to 7 years 3 months. The battery was published by the Psychological Corporation in San Antonio, Texas and can be purchased in its complete kit test entirety for $682.50. This price includes the test manual, testing materials (books complete with pictures for testing) and scoring sheets. Additional materials for testing including utensils like pencils, stop watch, clipboard and extra paper are not included. The reported administration time is reported as 60-75 minutes, depending on the age of the child (Kaufman & Lichtenberger, p. 16).
Description of Test
The WPPSI-R consists of two scales: Verbal (M = 100, SD = 15) and Performance (M = 100, SD = 15). As the titles of the respective scales indicate, verbal scales require spoken responses while performance scales require pointing, placing or drawing. Each scale is comprised of five subtests and also includes one optional subtest for each scale. The performance subtests include the object assembly, block design, mazes, picture completion, and geometric design. Here the animal pegs procedure is the optional subtest. The verbal subtests include information, comprehension, arithmetic, vocabulary, and similarities with the sentence procedure being the optional sixth subtest. A brief description of each subtest is as follows:
Object Assembly (6 items): (a) placing pieces into a form board and (b) assembling jigsaw puzzles.
Block Design (14 items): the main objective is to replicate designs shown to the individual using three or four blocks.
Mazes (11 items): the main objective is to find paths through a series of mazes.
Picture Completion (28 items): the main objective is to identify the essential missing part of the picture.
Geometric Design (16 items): contains two different formats, to select matching design from four choices or copy a geometric design shown on a printed card.
Optional Animal Pegs: the main objective is to place appropriate colored pegs into the corresponding holes on a board.
Information (27 items): Reponses are required to questions such as “Point to the picture that shows the one you cut with”, “How many legs does a cat have?” or “How many pennies make a dime?”.
Comprehension (15 items): Responses are required to questions such as “why do you need to take a bath?” or “What makes a sailboat move?”.
Arithmetic (23 items): Responses are required to questions such as “Bill had 1 penny and his mother gave him 1 more. How many pennies does he now have?”.
Vocabulary (25 items): Responses are required to questions such as “What is a boot?”, “What does “nice” mean?” or What does “annoy” mean?”.
Similarities (20 items): Responses are required to questions such as “You can read a book and you can also read a _____?” or “In what way are a cow and a pig alike?”
Optional Sentences: the main objective is to repeat sentences given orally by the examiner.
As previously addressed, the appropriate age range for the WPPSI-R is 3 years to 7 years 3 months. This is the target age of children in preschool and elementary grades kindergarten through approximately second grade. The test would not be appropriate for children older than the designated age since more than likely, the questions on the test would be too easy (if given to a child with perceived “average/normal” development of intelligence). If the child is older than this designated age range, the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) would be the appropriate test to be administered.
Upon beginning the administering the WPPSI-R, the test administrator must take into consideration a couple of important factors that, if not completed properly, will effect the validity and reliability of the test. First and foremost, the place of testing should be one where there will be little to no distraction, i.e. outside noise, people continuously entering or exiting the room, lots of decorations on wall. Since this test is given to young children whose attention spans can be variable, the testing room or environment should be relatively contained and free of any unnecessary disturbances. Before beginning, the test administrator should be fully prepared with all the necessary materials, booklets, and scoring sheets needed to complete the test in the allotted time. If the test administrator has to fumble around for a pencil or stopwatch, the child may again become anxious or inpatient. When testing does begin, test administrators should either sit opposite the child or at a 90-degree angle from the child. This is important because either one of these recommended seating arrangements allows for maximum visibility and opportunity for the test administrator to document accurate responses from the child. As previously stated, total time for test administration is estimated at 60-75 minutes depending on the age of the child.
Three types of scores can be calculated after the administration of the WPPSI-R is given. They include raw scores, scaled scores, and IQs. The raw scores are a total of points earned on a single subtest and are essentially meaningless since it is not norm referenced. Scaled scores are easy to determine using the child’s original raw score. Using the child’s chronological age, the child’s raw score on all subtests, and two tables from the WPPSI-R manual from 1989, the scaled score corresponds to the age of the child. To calculate the full scale IQ, simply add the sum of the verbal and performance scales’ sums of scores. The verbal IQ score consists of the information, comprehension, arithmetic, vocabulary and similarities subtests while the performance IQ score consist of the object assembly, geometric design, block design, mazes and picture completion subtests. Scoring can be completed using all the provided materials from the test kit and can be done with relative ease by graduate students or trained adults.
The standardization sample for the WPPSI-R includes a sample of 1,700 children who were “chosen to closely match the 1986 U.S. Census data on variables of age, gender, geographic, region, ethnicity, and parental education and occupation” (Kaufman & Lichtenberger, p. 12). Euro American and non-Euro American children were also selected to compile the best representative sample possible. As a result, the WPPSI-R standardization sample is very good due to its stratified and representative sample. The distribution of scores including their mean and standard deviations for the performance scaled scores is 10 and 3 respectively and 100 and 15, respectively, for the IQ scores.
Across the board, the average internal consistency reliability and average test-retest reliability coefficients are good. The average internal consistency reliability for the performance IQ, verbal IQ and full scale IQ scores are .92, .95, and .96, respectively (Sattler, p. 338). These are excellent coefficients showing the test, according to internal consistency measures, accurately assesses the different ranges of performance, verbal and combined intelligence scores of children. For the verbal subtests, the internal consistency coefficients range from .80-.86 while the performance subtests have internal consistency coefficients ranging from .63-.85. Here we see a slight decrease in the psychometric property but .60 ranges is still decent. Test-retest reliability coefficients for both the performance and verbal subtests are lower than one would like. Test-retest coefficients range from .52-.82 for the performance subtests and .70-.81 for the verbal subtests. But for the overall performance IQ, verbal IQ and full scale IQ scores, the test-retest reliability is stronger with .88, .90, and .91 coefficients, respectively (Sattler, p. 338).
Looking at both the concurrent-related and construct validity of the WPPSI-R, researchers have documented that each category contains strong support for good overall test validity. Studies indicate that the WPPSI-R has acceptable concurrent validity with the median correlation between the WPPSI-R and various intelligence tests being .74(Sattler, p. 340). It should be noted here that although many believe the WPPSI-R and WISC-III very similar tests that assess intelligence, they are not parallel forms perhaps due to ceiling effects on the WPPSI-R. Construct validity is “supported by the factor analytic studies that show the WPPSI-R to be a two-factor test; one is clearly identified as Verbal and the other as Performance” (Kaufman & Lichtenberger, p. 14).
Summary and Conclusions
Aside from the well established norms, good reliability and validity proof the WPPSI-R has been documented to possess, I am able to discuss the test from a test administrator’s viewpoint. Although this past summer I administered the WPPSI-III, the overall similar structure and format it resembles to the WPPSI-R allows me to state that I believe this test to be a reliable and valid measure of cognitive ability. Testing preschool children has provided me with the opportunity to attest to its face validity and reliability because I tested over 30 children using both the verbal and performance subtests. The children I tested age ranged from 4 to 5 years of age and the majority of them completed the subtests administered. Also, the manual and scoring procedures are clear-cut and easy to understand which allows for less confusion on the part of the test administrator. I also noted that the children appeared to enjoy many of the performance subtests because of the interaction between that took place which did not leave them complacent or bored.
Strengths of the WPPSI-R include a well designed and fairly easily administration procedure on the part of the administrators, an excellent, large normative standardization sample and strong reliability and stability coefficients. Weaknesses of the test include a sometimes lengthy test administration period which may leave the children fatigued, agitated and less willing to participate. Also, in their assessment of the WPPSI-R, Kaufman & Lichtenberger (2000) suggested that, based on their own research, the “floor of some of the WPPSI-R subtests is unsatisfactory for the youngest children and certain subtests have poor stability coefficients” (p. 191). It should also be noted that many of these issues were addressed in the second revision of the WPPSI to the most current WPPSI-III.
The WPPSI-R also plays an important role in educational and clinical settings. Since the test purports to measure verbal and non-verbal intelligence, many school psychologists and clinical psychologists find it a valuable tool when assessing the overall cognitive abilities and/or lack of intelligence development in young children throughout school and clinical settings.
In 2002, the Psychological Corporation published the second revision of the WPPSI and titled it the WPPSI-III. The WPPSI-III contains a considerable amount of changes from the WPPSI-R including a lowered age range which allows it to be used for children as young as 2 years, 6 months, the addition of seven new subtests to “enhance the measurement of fluid reasoning, processing speed, and receptive, expressive vocabulary” (Kaplan & Saccuzzo, p. 275). In addition, the third revision of the test contains updated norms similar to those in the WISC-IV and based on the more current Census data of October 2000 (Hamilton & Burns, 2003). Currently, it was difficult for me to find peer-reviewed articles that investigated and analyzed the latest version of the test but more than likely the WPPSI-III will further our current understanding of intelligence in young children.
Overall, the WPPSI-R has more than adequate empirical documentation that shows the test contains sound psychometric properties that lend to its legitimacy as a staple in the intelligence assessment area of tests for young children. I predict that in another 10 to 15 years, the third revision will be published with a new and current standardization sample yet still contain the same stable psychometric properties.
Hamilton, W. & Burns, T. G. (2003). Review of WPPSI-III: Wechsler Preschool and Primary Scale of Intelligence (3rd Ed.). Applied Neuropsychology, 10(3), 188-190.
Kaplan, R. M., & Saccuzzo, D. P. (2005). The Wechsler Intelligence Scales: WAIS-III, WISC-IV, and WPPSI-III. In Psychological testing: Principles, applications, and issues (pp. 274-275). Belmont, CA: Thomson-Wadsworth.
Kaufman, A. S. & Lichtenberger E. O. (2000). Essentials of WISC-III and WPPSI-R assessment. New York, NY: John Wiley & Sons.
Sattler, J. M. (2001). Wechsler Preschool and primary scale of intelligence-revised. In Assessment of Children: Cognitive Applications (pp. 335-374). San Diego, CA: Jerome M. Sattler.