Paper presented at the First Annual South Padre Island Conference
on Cognitive Assessment of Children and Youth in School and Clinical Settings
November 26 & 27, 1993
A Compendium of Proceedings, p. 35-49
-------------------------------------------------------------------------------------------------------------
A Nonverbal Alternative to the Wechsler Scales:
The Snijders-Oomen Nonverbal Intelligence Tests
Dr. Peter Tellegen
Summary
The Snijders-Oomen Nonverbal Intelligence Tests are instruments that can be individually
administered to children for diagnostic purposes. The tests make a broad assessment of a
spectrum of intelligence functions possible without being dependent upon language skills.
Because the tests can be administered without the use of written or oral language, they are
suitable for use with children who are handicapped in the areas of communication and
language development. For the same reason, they are also suitable for use with immigrant and
bilingual children who do not have a good command of the language used by the examiner. In
this paper the test contents of the latest revision of the test for the younger children will be
described (SON-R 2.5-7, to be published in 1994), and the results of some small scale studies
into the relationship of the revision of the test for older children (SON-R 5.5-17) with other
intelligence measures. Special attention is given to aspects of administration which make the
tests child-friendly and more suited to children we become easily demotivated.
Introduction
Their dependency on language skills in test contents and instructions makes the Wechsler
scales less appropriate for the assessment of cognitive abilities of ethnic minorities and of
children with problems with verbal communication, such as deaf and hearing disabled
children and children with speech and language disorders. For these groups, low performance
on a general intelligence test like the WPPSI and the WISC might primarily reflect poor
verbal knowledge and/or little experience with the English language instead of limited
reasoning and learning ability. This does not imply that administration of the Wechsler tests
to these children would not provide valuable information. However, one should be aware of
the dangers in interpreting these scores as measures of overall intelligence. Also when the
interpretation is restricted to the Performance Scale, these objections are not fully overcome.
The instructions of the Performance part are given verbally and may be less well understood
by the particular groups mentioned above. Moreover, the subtests in this part load strongly on
the Perceptual dimension and are less focused on abstract reasoning abilities.
Nonverbal alternatives for intelligence assessment like Raven's Progressive Matrices (Raven,
Court & Raven, 1983) and the Test Of Nonverbal Intelligence (TONI-2; Brown, Sherbenou &
Johnson, 1990) have the drawback that they are unidimensional tests which do not allow for
generalizations to a broad area of intelligence.
In 1943 a nonverbal test series intended for deaf children was published by Mrs. Nan
Snijders-Oomen (Snijders-Oomen, 1943). This test, known as the SON test, included
nonverbal subtests related to abstract and concrete reasoning. In subsequent revisions the test
was standardized both for hearing and deaf children. The latest revision for children from 5
to 17 years appeared in 1989 (SON-R 5.5-17; Snijders, Tellegen & Laros, 1989); a new
revision for the younger children (the SON-R 2.5-7) will be published by the end of 1994.
These individually administered tests examine a broad spectrum of intelligence without being
dependent on language.
Although the construction of norms has until now remained constricted to the Netherlands,
manuals and scoring forms have always been translated into English and German and
research results with the tests with various groups of children have been published in many
countries. For instance, with deaf and hearing disabled children (Backer, 1966; Stachyra,
1971; Balkay & Engelmayer, 1974; Watts, 1979; Schaukowitsch, 1981; Zwiebel & Mertens,
1985), children with speech and language disorders (Grimm, 1987), children with learning
disabilities and mentally retarded children (Sarimsky, 1982; Schmitz, 1985; Eunicke-Morell,
1989), autistic children (Steinhausen, Goebel, Breinlinger & Wohlleben, 1986; SüssBurghart, 1993), motor handicapped children (Colin, Frischmann-Rosner, Liard & Magne,
1974; Constantin, 1975), children from ethnic minority groups (de Vries & Bunjes, 1989;
Eldering & Vedder, 1992), normal children (Malhotra, 1972; Harris, 1979, 1982; Ditton,
1983; Melchers, 1986 ; Wolf, 1991; van Aken, 1992) and psychiatric patients (Plaum, 1975;
Plaum & Duhm, 1985).
Detailed information on the construction, the administration, the reliability and the validity of
the SON-R 5.5-17 can be found in the manual (Snijders, Tellegen & Laros, 1989) and in the
dissertation by Laros & Tellegen (1991). A summary was recently published in the European
Journal of Psychological Assessment (Tellegen & Laros, 1993). In this paper we will focus on
a description of the revised SON-R 2.5-7 and we will give a summary of some small-scale
studies, performed by other researchers, into the relationship of the SON-R 5.5-17 with other
intelligence tests.
The SON-R 2.5-7
The last revision of the Pre-school-SON took place in 1975 (Snijders-Oomen, 1976). After
such a period of time a revision is needed because the norms and the data concerning
reliability and validity are subject to obsolescence. An important goal of the revision was to
make the test more suitable for the youngest and the oldest age groups by enlarging the item
set with very easy and with more difficult items. This resulted in almost a doubling of the
number of items. However by skipping items at the beginning of the subtests for older or
more able children and by discontinuation after, at the most, three errors, the total testing time
required is about an hour on the average.
In the composition of the SON-R 2.5-7 we have tried to connect the test with the SON-R 5.517. For this purpose, a number of subtests have been developed that appear in both tests. The
easiest items in the subtests of the SON-R 5.5-17 are the basis for the most difficult items in
the comparable subtests of the SON-R 2.5-7. Therefore, it seems plausible that both tests
measure intelligence in the same manner for the overlapping age range (Tellegen, Wijnberg,
Laros, Winkel, 1992).
In the following a short description of each subtest will be given. The subtests in the SON-R
2.5-7 are: 1. Mosaics, 2. Categories, 3. Puzzles, 4. Analogies, 5. Situations and 6. Patterns.
The six subtests are composed of 14 to 17 items that increase in level of difficulty. The
subtests each have two parts. These two parts differ in materials and instruction. In the first
part examples are incorporated in the items; the second part of each subtest is preceded by an
example and the remaining items are solved by the subject independently.
Mosaics
Mosaics consists of 15 items and 1 example item. In part I the child is required to copy
different simple mosaic patterns in a frame using three to five red squares. The difficulty is
determined by the number of squares to be used and whether or not the examiner first
demonstrates the item.
In part II diverse mosaic patterns are copied in a frame using red, yellow and red/yellow
squares. Each mosaic pattern consists of 9 squares; that correspond to the parts of the pattern.
In the easiest items of part II only red and yellow squares are used, and the pattern is printed
in the actual size. In the most difficult items all of the squares are used and the pattern is
scaled down. The squares are 32 mm by 32 mm and are printed with the same colors on both
sides.
Categories
Categories consists of 15 items and 1 example item. In part I four to six cards must be sorted
into the correct category. In the first few items the drawings on the cards belonging to one
category strongly resemble each other. For example, a shoe shown in different positions. In
the last items of part I the concept lying behind the category must be understood in order to
complete the item successfully. For example, vehicles that have a motor contrasting with
those that do not.
Part II is multiple choice. In this part the child sees three pictures of objects that have
something in common. Two pictures that have the same thing in common have to be chosen
from another column of five pictures. The level of difficulty is determined by the amount of
abstraction in the characteristic.
Puzzles
Puzzles consists of 14 items and 1 example item. In part I puzzles must be laid in a frame to
resemble the given example. These puzzles each have three pieces. The first few puzzles are
first demonstrated by the examiner. The most difficult puzzles in part I have to be
independently solved.
In part II a whole must be formed from 3 to 6 puzzle pieces. No instructions are given as to
what the puzzles should represent; the frame is no longer used. The number of puzzle pieces
partially determines the level of difficulty.
Analogies
Analogies consists of 17 items and 1 example item. Analogies is the only subtest in which
two different test booklets are used for parts I and II. In Analogies I the child is required to
sort blocks into two boxes on the basis of either form, color, size, or a combination of the
three. The child must discover the sorting principle him or herself. In the first few items the
blocks to be sorted are generally the same as the ones pictured in the test booklet. In the last
items of part I the child must discover the principle independently. For example large versus
small blocks.
Analogies II is multiple choice. Each item consists of an example analogy in which a
geometric figure changes in one or more aspects to form another geometric figure. The
examiner demonstrates a similar change. The same principle is used. The examiner and child
together choose the correct alternative from a number of possibilities. Following this the child
has to apply the same change to another figure and choose the correct alternative
independently. The child must point to the correct alternative. The level of difficulty in the
items is related to the number and complexity of the transformations.
Situations
Situation consists of 14 items and 1 example item. Part I consists of items in which 4 pictures
are shown in the booklet with half of each picture missing. The child has to place the halves
in the correct picture. The first item is printed in color in order to make the principle clear.
The level of difficulty is determined by the amount of similarity between the different halves
belonging to an item.
Part II is multiple choice. Each item consists of a drawn situation from which one or more
pieces are missing. The correct piece (or pieces) must be chosen from a number of
alternatives in order to make the situation logically consistent.
Patterns
Patterns consists of 16 items. The child is required to copy an example pattern using a pencil.
The first items are drawn freely, then dots have to be connected in order to make the pattern
resemble the example. The first few items are first demonstrated by the examiner and consist
of not more than 5 dots. The last items consist of 9 or 16 dots and are to be directly (and
independently) copied by the child.
Four types of subtests have always been represented in the SON-tests: abstract reasoning
tests, concrete reasoning tests, spatial tests and memory tests. In the composition of the SONR 5.5-17 this was changed: a test for memory was not included in the test series. The authors
of the test consider research on memory to be a separate field that no longer fits within the
margins of intelligence testing (Snijders, Tellegen & Laros, 1988, p.20). For the same reason
no memory test has been included in the present revision of the Pre-School-SON.
Tests of reasoning generally form the core of most intelligence tests. They can be divided into
abstract and concrete reasoning tests. Abstract reasoning tests (Categories and Analogies)
depend on relations between concepts that are abstract, namely, not bound to time or space. A
principle for ordering must be derived from the test materials that has to be applied to new
materials.
Concrete reasoning tests (Puzzles and Situations) refer to persons or objects that are bound
together by space and time. The accent can be placed on the either the spatial or the time
dimension, this leads to different types of tests. The SON-R 2.5-7 only includes tests in which
the spatial dimension is emphasized.
Spatial tests (Mosaics and Patterns) resemble concrete reasoning tests in that by both a
relationship must be seen within a spatial whole. In concrete reasoning tests the emphasis lies
on conceiving meaningful relations between parts of a picture, in spatial tests on form
relations between parts of a figure.
The instructions to the test can be given verbally or in a nonverbal way by gestures or by a
combination of both. An important aspect of the instructions is demonstration by the
examiner. Care has been taken not to give extra information in the verbal instruction by
naming objects or concepts. This flexibility in the way the instructions are given allows for a
natural and stimulating contact. The communication can be adapted to the normal ways of
interacting with a particular child.
Another important aspect of administering the test is that feedback is given after each item. In
the SON-R 5.5-17 this feedback is limited to telling the child whether the answer is correct or
incorrect. In the SON-R 2.5-7 the correct solution is always demonstrated to the child by the
examiner. If possible, just a little help will be given so the child can complete the item by him
or herself. This feedback also allows for a more natural interaction between examiner and the
child and it gives the child a better understanding of the requirements of the task in case the
instructions have not been fully understood. In this respect there is a close resemblance
between the SON tests and tests based on the ideas of Learning Potential Assessment
(Tellegen & Laros, 1993).
Test norms will be based on a stratified sample of 1100 children (eleven half-year groups
from two years and three months up to seven years and three months. This standardization
research was performed in the second half of 1993. Data on the reliability and factorial
structure will be available later this year. Extensive research is being performed for the
validation of the tests. This includes the relationship with other intelligence measures and
tests on language development, memory and perception and research with special groups of
children for whom the test seems especially appropriate. Among these groups are children
with hearing-, speech- and language disorders, deaf children, children with learning problems,
autistic children, and immigrant children for whom Dutch is often second language. An
extensive account of this research, which will be performed partly in Australia and the USA,
will be published in the manual.
The SON-R 5.5-17
In this section the results of three small-scale studies into the relationship of the SON-R with
other intelligence tests will be summarized. They were performed by other researchers after
the publication of the SON-R 5.5-17.
Relation with WISC-R and Raven Progressive Matrices (Nieuwenhuys, 1991)
A group of 35 children from an outdoor psychiatric university clinic were tested with the
SON-R, the WISC-R and the Raven Progressive Matrices Test. The age range was from 6 to
16 years and there were no immigrant children in the sample. The WISC-R (Van der Steene
et al, 1991) has recently been standardized for the Dutch population. For the Raven (Raven,
Court & Raven, 1983) English norms were used; eight groups of percentile scores were
transformed to standard scores. Administration of the SON-R and the WISC-R was alternated
within a period of two weeks. The Raven was generally combined with one of the other tests.
For the SON-R the standard IQ was used. In the following table the means and standard
deviations, and the correlations between the IQ scores are presented.
Table 1. A comparison of SON-R 5.5-17, WISC-R and Raven Progressive Matrices
___________________________________________________________________________
correlations
-------------------------------------------VIQ PIQ FSIQ Raven SON-R
mean sd
--------------------------------------------------------------------------------------------------------VIQ
.65
.55
.66
95.5 13.9
WISC-R
PIQ
.65
.74
.80
96.8 17.8
FSIQ
.71
.80
95.6 15.9
Raven Prog. Matrices
.55
.74
.71
-
.74
96.1
11.4
SON-R 5.5-17
.66
.80
.80
.74
97.8 15.8
__________________________________________________________________________
There is a great similarity in the means of the IQ scores. Paired t-tests showed no significant
differences between the means. Also the standard deviation of the WISC FSIQ was equal to
standard deviation of SON-R IQ. The standard deviation of the Raven was substantially lower
but the norms of that test are not comparable. There are substantial high correlations of .80
between the SON-R IQ and the WISC-R FSIQ and PIQ. The correlations of the SON-R IQ
and the PIQ with the verbal scale of the WISC-R are about the same (.66 and .65) and both
scores correlate .74 with the Raven. Compared to the Raven, the SON-R shows higher
correlations with all the IQ scores of the WISC-R.
Relation of SON-R with four WISC-R verbal scales (Jansen, 1991)
Fourteen children from 6 to 12 years, who had been diagnosed as having specific language
impairment at a center for speech and language disorders, were re-assessed after several years
with four verbal tests from the WISC-R and with the SON-R. For these children there still
existed a large discrepancy between verbal intelligence as measured by the WISC-R VIQ
(mean = 83.1; sd = 14.8) and nonverbal intelligence as measured with the SON-R (mean =
97.5; sd = 14.0). The difference was significant at the .01 level. In this particular group the
correlation of the SON-R IQ with the VIQ was moderate, r=.35, and not significant.
Relation of SON-R with LEM (Veerman, 1993)
At a school for deaf children a comparison was made between the performance of 14 children
(age-range 5 to 7 years) on the SON-R and on an adapted version of the Learning test for
Ethnic Minorities (Hessels & Hamers, 1993). The LEM is a nonverbal test, based on theories
of learning potential assessment, in which help is given to the subject during administration.
The means and standard deviations were very similar for the SON-R (mean = 101.3; sd =
21.2) and the LEM (mean = 101.4; sd = 20.6). The correlation between the standardized total
scores was high (r=.86). The SON-R correlated .70 with teacher's assessment of intelligence
on a three-point scale; the LEM .63.
Discussion
For those situations in which intelligence assessment is required by means of a test battery
which is not dependent on specific language skills, the SON tests seem to be a good, and
maybe the only, sensible alternative. Nonverbal tests like the Raven and TONI-2 cannot be
considered as alternatives either for the Wechsler scales or for the SON tests because they are
so much limited in contents and do not allow for generalizations to a broad area of
intelligence. This is illustrated by the higher correlations of the SON-R with the WISC-R
compared to the Raven.
Another question might be whether the performance part of the Wechsler tests could not be
used as a substitute for a nonverbal test. However, they use verbal instructions and they seem
more limited in contents compared to the SON tests. Although we would expect the
correlation of the SON-R with the WISC-R VIQ to be higher compared to the correlation
between PIQ and VIQ this was not the case in the research by Nieuwenhuys. Two factors may
have contributed to a relative underestimation of the correlation of the SON-R with both the
VIQ and PIQ. Because administration of the complete WISC was done in one session (with
verbal and performance subtests alternated) and the administration of the SON-R took place
some weeks earlier or later, any order effects of testing and day to day variations in
motivation, concentration, well being and, as a result, in performance will have had adverse
effects on the correlation of the SON-R with the VIQ but not on the correlation of the PIQ
with the VIQ. For a better comparison also the verbal and the performance part of the WISC
should be separated in time.
An important difference between the SON-tests and other nonverbal intelligence tests is the
flexibility in the use of language and gestures in giving the instructions. For instance with the
UNIT (Universal Nonverbal Intelligence Test), a nonverbal test series that is being developed
by Bracken & McCallum, no verbal communication is allowed during the administration of
the subtests and there are strict rules for the gestures that are allowed. Although the flexibility
that is allowed with the SON tests might make these tests less standardized, we expect that a
more natural communication with the child will contribute to the validity of the results. Too
strong an emphasis on the objectivity of administrative rules can have undesirable effects on
the motivation of the subjects and on the comprehension of the tasks.
The way feedback is given to the children with the SON-R 2.5-7 also contributes to a natural
and cooperative interaction between the examiner and the child. Moreover, because the
subtests are discontinued after three errors in total, feelings of failure will not so easily arise
as with the Wechsler tests which generally require five consecutive errors. All these factors
make the test pleasant to do, not only for most children but also for the examiner. For this
reason the SON tests are not only useful instruments for children with problems in the area of
language and communication, but for all children, and especially the young ones, for whom
motivation is of prime importance for valid assessment and diagnostic purposes.
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