Theory and Practice
J. P. DAS University of Alberta
JACK A. NAGLIERI
George Mason University
It is almost a truism that a test has to have a theory that makes it intelligible and guides its interpretation. The Das-Naglieri Cognitive Assessment Sys- tem (CAS; Naglieri & Das, 1997a) not only is a relatively new measure of in- tellectual ability, but also heralds the beginning of a new way of looking at in- telligence. The reconceptualization of intelligence rides, as it were, on the coattails of information processing theory that ushered in the cognitive rew olution. Essentially, the theoretical base of the CAS is cognitive psychology and neuropsychology as integrated in PASS theory; PASS is an acronym for the four major cognitive functions, which are Planning, Attention, Simulta- neous, and Successive processing (Das, Naglieri, & Kirby, 1994).
Consistent with cognitive psychological research, PASS theory aims at un- raveling the cognitive processes that determine performance on the CAS. In line with neuropsychological research, the processes are multidimensional, reflecting the interdependent workings of functional regions of the brain. We do not believe that a unidimensional undifferentiated mass of "general abil- ity" (the so-called g) is very useful for understanding the variety of intellectual abilities that characterize individuals. Neither is the concept of g informa- tive in establishing a profile of children's cognitive processing for diagnosis
Handbook of Psychoeducational Assessment
Copyright 9 2001 by Academic Press. All rights of reproduction in any form reserved. 33
of learning and attentional difficulties, for example. Additionally, a global unitary IQ score cannot guide instruction or suggest remediation. The ad- vantages of PASS theory and its operationalization in the CAS will become apparent throughout this chapter.
We shall begin our presentation with a short introduction to PASS theory, delineating its neuropsychological basis (mainly influenced by Luria) and describing the four cognitive functions. This will be followed by a practical presentation of the CAS, including a discussion of its structure and admin- istration as well as interpretation of the test scores. Finally, we will discuss the prediction of school achievement vis-t~-vis other contemporary tests. Be- cause assessment alonemwithout an implication for what to do next with the child who was assessedmis no longer enough, we briefly discuss the value of PASS theory and the CAS in guiding intervention that can ameliorate the cognitive difficulties identified by the CAS. The focus of the whole chap- ter is to provide a basic theoretical understanding of cognitive processes, de- tailed information about assessment procedures, and discussion of some possibilities for intervention, all as they apply to the individual child.
PASS P R O C E S S E S AND THE FOUR FUNCTIONAL REGIONS OF THE BRAIN
Function is the core concept of Luria's functional organization of cognitive pro- cesses in the brain. Luria (1973) distinguishes a functional system from a static notion of abilities as follows: "The presence of a constant task, per- formed by variable (variative) mechanisms, bringing the process to a con- sistent (invariant) result is one of the basic features distinguishing the work of every functional system" (p. 28). Functional systems, according to Luria, have both depth and spread. Processing of information in simultaneous quasi- spatial arrays, for example, is spread over a large area of the occipital and parietal lobes. Successive information processing--that is, ordering infor- mation temporallymlikewise is broadly localized in the temporal and fronto- temporal areas of the brain. Planning and making decisions may inhere in the whole of the frontal lobes.
Any kind of information that is received through the senses must go through a coding process, such as coding of visual information, and passes through three hierarchical levels of the brain. The first level may be described simply as the projection area, where the modality characteristic of the infor- mation is intact. The second level, above the projection area, is referred to as the projection-association area. As information reaches this area, it loses part of its modality tag; visual and auditory experiences (e.g., the sights and sounds of a car accident) become fused together so that it becomes difficult to say with certainty if a specific piece of "eyewitness" information was seen rather than heard. Above the projection-association area is the third (terti- ary) level, which consists of overlapping zones, where information is typically
amalgamated and the modality tags are absent. This grand amalgamation is necessary because it allows information to be integrated from different sen- sory organs without any separation due to modality of input; this subse- quently makes it easier to act on the information.
Luria (1966, 1980, 1982) described human cognitive processes within a framework of three functional blocks or units. The first unit regulates cortical arousal and attention; the second unit codes information using simultane- ous and successive processes; and the third unit provides for planning, self- monitoring, and structuring of cognitive activities. Luria's work on the func- tional aspects of brain structures formed the basis of the PASS theory, and it was used as a blueprint for defining the important components of human in- tellectual competence that could then be assessed by the CAS. The four PASS processes and their essential features are summarized in the following sec- tion, which also provides a rationale for the construction of the CAS tests.
PASS AND THE A S S E S S M E N T OF COGNITIVE P R O C E S S E S BY CAS
The CAS (Naglieri & Das, 1997a) is based on the PASS theory and is designed to integrate contemporary cognitive psychological and neuropsychological theory with psychometrics, because "psychological measurement, no matter how direct, has little meaning unless it is theory based" (Crocker & Algina, 1986). PASS theory, and its application in the CAS, recognizes that human cognitive functioning includes four components situated within the knowl- edge base of the individual. These components are: (1) planningmthe con- trol processes of cognition, executive functions, strategy, and intentionality;
(2) attentionmfocused cognitive activity and resistance to distraction; and (3) simultaneous and (4) successive processingmthe two forms of operating on information.
Planning is the mental process by which a person determines, selects, and uses efficient solutions to problems. It involves problem solving, formation of mental representations, impulse control, control of processing, and re- trieval of knowledge.
Attention is the process that allows us to selectively attend to some stimuli while ignoring others. It involves focused cognitive activity, and its key ele- ments are selective attention, resistance to distraction, orienting response, vigilance, and reticular formation as substrate.
Simultaneous processing integrates stimuli into groups. Stimuli are seen as whole, or gestalt, each piece being related to the others. Simultaneous pro~
cessing is associated with the integrity of the parieto-occipital-temporal re- gions and can involve verbal or nonverbal stimuli.
Successive processing integrates stimuli in a specific serial order, forming a chain-like progression of stimuli. Successive processing can involve verbal or nonverbal stimuli and is associated with the fronto-temporal regions.
PASS
9 Cognition is information processing 9 Supports functional segmentation of brain 9 Cognitive processes define intelligence
9 Four processes: Planning, Attention, Simultaneous, and Successive
Knowledge Base
9 Tacit, and Experiential and Spontaneous OR Explicit and Instructed 9 Both types reside in long-term memory
9 Working memory is actively used in PASS
Input
External: visual, auditory, etc., presented all at once or one after another Internal: images and thoughts accessed from knowledge base
Output In three modes:
M o v e m e n t - - g r o s s and fine Mimetic u gestures, dance, music
L a n g u a g e - - o r a l and written, graphics, sign
F I G U R E 2. I
PASS theory of cognition.
A schematic presentation of PASS theory is shown in Figure 2.1. The figure begins by emphasizing that PASS processes provide a theoretical view of ability considerably different from the traditional approach of general intelli- gence. Next, the importance of knowledge and skills is noted, along with the types of input and output.
CAS DESCRIPTION
The CAS is an individually administered test designed for children and ado- lescents aged 5 through 17 years. The test consists of 12 regularly adminis- tered subtests, which are organized into four PASS Scales. There is also a to-
TABLE 2.1
Organization of the CAS Scales and Subtests (Standard Battery) Full Scale
Planning
Matching Numbers a Planned Codes ~ Planned Connections Simultaneous
Nonverbal Matrices ~ Verbal-Spatial Relations ~ Figure Memory
Attention
Expressive Attention ~ Number Detection a Receptive Attention Successive
Word Series a Sentence Repetition ~
Speech Rate (ages 5-7 years) or Sentence Questions (ages 8-17 years) aSubtests in each PASS Scale that are included in the CAS Basic Battery.
tal score, called a Full Scale. The PASS Scales and Full Scale standard scores can be obtained using two combinations of subtests. One combination is called the Basic Battery and the other is called the Standard Battery. The Bar sic Battery includes 8 subtests (two per PASS Scale); the Standard Battery includes all 12 subtests, as shown in Table 2.1.
Full Scale
The Full Scale (FS) score is an overall measure of cognitive functioning, with a mean (M) set at 100 and a standard deviation (SD) set at 15. The score yields a measure of the child's overall level of cognitive functioning based on the four PASS Scales.
PASS Scales
The PASS Scale scores (each with an M of 100 and an SD of 15) are composed of the sum of subtest scaled scores included in each respective scale. These scores represent a child's cognitive functioning in specific areas and are used to identify specific strengths and weaknesses in cognitive processing. The PASS Scales, not the PASS subtests, are the focus of CAS interpretation.
Subtests
The subtests (each set at an M of 10 and an SD of 3) are measures of the specific PASS process corresponding to the scale on which they are found.
They are not considered to represent their own set of specific abilities, but rather are measures of one of the four types of processes. They do vary in con- tent (some are verbal, some are not; some involve memory, others do not;
etc.), but the most important point is that each is an effective measure of a specific PASS process.
Standardization
The CAS was standardized for children aged 5-17 years, using a stratified random sampling plan that resulted in a sample that closely matches the U.S. population. Children from both regular education and special education settings were included. During the standardization and validity study data- collection program, the CAS was administered to a total of 3072 children.
Of that sample, 2200 children made up the normative sample and an addi- tional 872 children participated in reliability and validity studies. A group of achievement tests was also administered to a 1600-person subsample of the 2200-person standardization group.
The CAS standardization sample was stratified on the basis of Age (5 years 0 months through 17 years 11 months); Gender (Female, Male); Race (Black, White, Asian, Native American, Other); Hispanic origin (Hispanic, Non- Hispanic); Region (Midwest, Northeast, South, West); Community Setting (Urban/Suburban, Rural); Classroom Placement (Full-Time Regular Class- room, Part-Time Special Education Resource, Full-Time Self-Contained Special Education); Educational Classification (Learning Disability, Speech/
Language Impairment, Social-Emotional Disability, Mental Retardation, Giftedness, and Non-Special Education); and Parental Educational At- tainment Level (less than high school degree, high school graduate or equiv- alent, some college or technical school, four or more years of college). The methods used to collect the data were designed to yield high-quality data on a sample that closely represents the U.S. population; for details on the rep- resentativeness of the sample, see the CAS Interpretive Handbook (Naglieri
& Das, 1997b).
Administration
The CAS, like other tests of its kind, must be administered and scored as pre- scribed in the test's Administration and Scoring Manual (Naglieri & Das, 1997c). It is, of course, the obligation of the user to ensure that administra- tion is consistent with applicable professional standards and that an appro- priate environment is maintained. For example, developing and maintaining rapport, as well as following directions precisely, are important. Only a few
important points regarding administration of the CAS will be discussed in this chapter.
Administration Directions
The instructions to the child include both spoken statements and nonverbal actions by the examiner. Examiners need to carefully follow the instructions for gestures (indicated in parenthetical statements following or preceding the text) corresponding to the oral directions. The combination of oral and nonverbal communication is designed to ensure that the child understands the task.
Subtest Administration Order
It is important to administer the CAS subtests in the prescribed order, to re- tain the integrity of the test and reduce the influence of extraneous variables on the child's performance. For example, the Planning subtests are adminis- tered first, because they give the child flexibility to solve the items in any manner. In contrast, the Attention subtests must be completed in the pre- scribed order (i.e., left to right and top to bottom). By administering the Plan- ning subtests before the Attention subtests, the amount of constraint in- creases over time. If the Attention subtests were administered before the Planning ones, the rigid instructions for the Attention subtests might inhibit the child's performance on subsequent Planning subtests.
Strategy Assessment Phase of the Planning Subtests
All the CAS Planning subtests include a phase called Strategy Assessment, during which the examiner observes whether the child uses strategies to complete the items. Strategy Assessment was developed to gather informa- tion about how the child completes the items. In addition, it is used to help describe the standard scores that are obtained (see sections on Scoring and Interpretation, later in this chapter). Strategy Assessment information allows the examiner to describe the standard score in relation to the percentage of children within the standardization sample who used that particular strategy.
This description can help explain a particularly high or low Planning score and can be integrated into the entire evaluation.
Strategy Assessment is conducted for each Planning subtest in two ways.
Observed Strategies are those seen by the examiner through careful obser- vation at the time the child completes the items. Reported Strategies are ob- tained following completion of the item(s); the examiner elicits this informa- tion by saying, "Tell me how you did these," or "How did you find what you were looking for?" or some similar statement. The child can communicate the strategies by either verbal or nonverbal (gesturing) means. Information is
recorded in the "Observed" and "Reported" sections of the Strategy Assess- ment Checklist included in the Record Form.
"Provide Help" Guidelines
Several methods, including presentation of samples and demonstration items as well as opportunities for the examiner to clarify the requirements of the task, have been used to ensure that the child understands what is being requested. If, however, the child does not seem ready or appears in any way confused or uncertain, the examiner is instructed to "provide a brief expla- nation if necessary" (Naglieri & Das, 1997c, p. 8). This instruction gives the examiner freedom to provide explanation by any appropriate means, to en- sure that the child understands the task. The explanation can be in any form, including gestures, verbal statements, or other communication in any lan- guage. The intent is to give the examiner full decision-making authority to clarify the demands of the subtest, and to enable the examiner to be certain that the child understands what to do. The freedom to "provide help," how- ever, is not to be construed to mean the examiner can teach the child how to do the test.
Administration of the CAS to Bilingual or Hearing~lmpaired Children
Instructions for administration of the CAS were designed so that a child with an adequate working knowledge of English can benefit from the samples and demonstrations provided. In those cases where additional help is needed, examiners may augment the English instructions when the "provide addi- tional help when needed" prompt is given. During these introductory points where the subtest goals are being communicated, examiners who know the child's native language or who can use sign language may, when instructed, provide necessary assistance. In such cases, the examiner must decide when it is appropriate to use the alternative method of communication.
Age Partition
Children aged 5-7 and 8-17 years are given different instructions, and in some cases different sets of items, to allow testing to be tailored to particu- lar age groups. For example, two of the Attention subtests have different types of stimuli so that the content of the test can be made more appropri- ate for children in either age group. Specialized content was selected to en- sure that 5- to 7-year-olds would easily understand the items and that older children would not view subtests as too infantile. For example, Expressive At~
tention contains pictures of animals for 5~ to 7~year-olds but is composed of words for 8~ to 17-year~olds. Similarly, Speech Rate is administered only
to children aged 5-7 years and Sentence Questions only to children aged 8- 17 years, so that the task given to each group is age-appropriate. In addition, children aged 8-17 typically begin with more advanced items on some of the subtests.
Discontinue Rule
Administration of some subtests is discontinued after failure on four con- secutively numbered items. This applies to all Simultaneous subtests and to all but one of the Successive subtests (i.e., Speech Rate).
Time Limits
The time limits for various items vary, as shown in the Administration Direc- tions manual and the Record Form. These limits are provided in total seconds (e.g., 150) as well as in minutes and seconds (e.g., 2:30), to accommodate professionals who use a digital stopwatch and those who use an analog stop- watch. The point at which to begin timing is indicted within the directions found in the Administration and Scoring Manual. Following these instruc- tions carefully will ensure accurate evaluation of the time a child takes to complete the items. Where time limits are not provided (e.g., Nonverbal Ma- trices), examiners should exercise good judgment about when to encourage the child to attempt the next item.
Rates of Presentation of Stimuli
Six subtests require stimuli to be presented at a specific rate or for an exact period of time. Word Series requires administration at the rate of 1 word per second, and Sentence Repetition and Sentence Questions are presented at the rate of 2 words per second. Figure Memory involves stimuli that are pre~
sented for exactly 5 seconds. There is also a 30-second exposure time limit for each item in the Verbal~Spatial Relations subtest. These time limits must be followed exactly.
Spoiled Subtests
If one of the three regularly administered subtests in the Standard Battery is spoiled, examiners should use the remaining two subtests and compute the PASS Scale using the Basic Battery norms. Because the Full Scale may be based on either 8 or 12 subtests, the calculation of the Full Scale would then be computed using the Basic, not the Standard, Battery. Alternatively, exam- iners may prorate the sum of three subtests in the PASS scale using the table provided by Naglieri (1999).
Scoring the CAS
The CAS is scored using procedures that are typical in the field of intellectual assessment.
1. Subtest raw scores are obtained.
2. Raw scores are converted to subtest scaled scores.
3. PASS Scale and CAS Full Scale standard scores are obtained from the sum of the respective subtest scaled scores.
Subtest Raw Scores
The CAS subtest raw scores are calculated using one or more of the following methods: (a) number correct, (b) time to completion, and (c) number of false detections. These measurements are used either in isolation or in combina- tion, depending on the goals of the subtest. Some subtest raw scores are based on number correct; others are based on total time; and some are the combination of number correct and total time, or number correct, total time, and number of false detections. Each of the raw score methods is more fully described below.
Number Correct. Nonverbal Matrices, Verbal-Spatial Relations, Figure Memory, Word Series, Sentence Repetition, and Sentence Questions sub- tests are scored using the number of items correct. This is obtained by sum- ming the number of correct items and assigning credit for those items not ad- ministered below any starting point.
Time in Seconds. The raw score for Planned Connections and Speech Rate is the sum of the time (in seconds) taken to complete all items. To com- pute the raw score, simply add the time scores for the items administered.
Time and Number Correct. The raw scores for the Matching Numbers, Planned Codes, and Expressive Attention subtests are based on the combi- nation of time and number correct. The number correct and time are com- bined into a ratio score using a Ratio Score Conversion Table included in the Record Form. This table has a heading called "Accuracy Score" at the top, and the leftmost column contains time scores in 3-second intervals. To combine the number correct and time into a ratio score, find the row that contains the item time in seconds; then find the column for the Accuracy Score earned by the child. The number at the juncture of the row and column is the ratio score for that item. For example, if a child earned a total time score of 43 seconds with an accuracy score of 38, then the ratio score is 54. The ratio scores for each item are summed, as indicated on the Record Form, to obtain a raw score for the subtest.
Time, Number Correct, and Number of False Detections. T h e r a w s c o r e s for Number Detection and Receptive Attention are obtained using ratio