Tests and Procedures

Intelligence tests

The Performance Scale of the age-appropriate Wechsler intelligence scale (WISC-III, Wechsler, Golombok & Rust, 1992; WAIS-R, Wechsler, 1986) was administered. This included the following subtests: Picture Completion, Picture Arrangement, Block Design, Object Assembly and Coding (Digit Symbol). Performance intelligence quotients (PIQ) and scaled scores for each subtest were calculated according to instructions in the test manuals.

Receptive language tests

Receptive vocabulary (Lexical decision)

Thirty words and 30 nonwords (selected from those used in the Word and Nonword Repetition test; Cathercole& Baddeley, 1989) were read to each participant in a fixed random order. Participants were asked to indicate whether each word was a real word or a nonsense word. Responses were recorded and scored as number correct out of 60.

Receptive grammar

The Test for Reception of Grammar (TROC; Bishop, 1982) was administered. Participants heard a sentence and were required to indicate which one of four pictures matched the sentence. The test consists of 80 sentences, presented in blocks of four, each block testing a different syntactic contrast. This test is used clinically to assess receptive grammar in children between four and 12 years. Blocks are failed if one of the four sentences in a block is incorrectly matched with a picture. Standard scores are obtained based on the number of blocks passed. In this study, the participants were older than the oldest age group for which normative data are available (i.e. 12 years). Therefore scores were calculated as number of correct sentences out of a total of 80. In addition, the scores for 16 sentences from blocks L, N, R and T, which specifically examine embedded relative clauses (see Table 3.2), were calculated.

Table 3.2 Examples from the TROG assessing embedded relative clauses Block Syntactic contrast assessed Example o f test sentence

L reversible passive the elephant is pushed by the boy N postmodified subject the circle in the star is yellow

R relative clause the pencil is on the book that is yellow T embedded sentence the cat the cow chases is black

Expressive language te sts Word and nonword repetition

A list of 40 words and one of 40 nonwords (Gathercole & Baddeley, 1989) were read to each participant who was required to repeat each item. The words ranged from two to five syllables in length and the nonwords from one to four syllables. There were ten words and nonwords at each syllable length. Half of the words and nonwords contained only single consonants (e.g. killer, rubid), thus requiring simple articulatory output; the other half contained consonant clusters (e.g. thimble, hampent) requiring more complex articulation. During testing, each response was scored as either correct or incorrect and the scoring was later verified by reviewing the recorded audio- or videotape. Total scores out of 40 were obtained separately for the word and nonword versions of the test, along with scores out of five for either simple or complex articulation at each syllable length.

Naming

The Wingfield-Oldfield Object Naming test was administered (Oldfield & Wingfield, 1965). This test consists of 36 pictures that the participant has to name upon confrontation. The first clear response spoken was scored; response latencies were recorded using a stop watch. Each item was recorded as correct or incorrect out of a maximum score of 36. An average response latency was calculated for the items correctly named.

Verbal Eluency

Verbal oral fluency was assessed by asking each participant to generate words that either began with a specific letter (phonemic category) or belonged to a semantic category. The two letters were F and M and the two semantic categories

were fruit and animals. The number of words generated in two minutes was recorded, and separate average scores were calculated for phonemic and semantic fluency.

Written fluency was assessed by asking participants to write words beginning with the letter S, Participants were told not to be concerned about spelling, although this was checked after completion of the timed test. The number of words beginning with the letter S generated in five minutes was recorded. Different forms of the same word (e.g. swim, swims, swimming, swimmer) were only counted as one instance of the word.

Inflectional and derivational morphological production

Word and nonword versions of a test of morphological production were administered (Vargha Khadem et a l 1991). The participants were shown a picture while hstening to a pair of sentences read by the examiner. Twenty pairs of sentences were used in each version. In the word version, the first sentence contained a word that could be modified to complete the second sentence, (e.g. ''Look at how small these elephants are. This one over here must be the smallest”). In the nonword version, novel creatures were used in the pictures and nonwords were presented in the first sentence to be modified in completion of the second sentence, (e.g. "This creature is snozzing. We call him a snozzer”). Modifications required the change or addition of a final morpheme, (e.g. -est, or -er, in the examples above). In each of the versions, ten words required a derivational morpheme (i.e. a morpheme that alters the meaning of the word, sometimes changing its grammatical class; e.g. "This boy has lots of spots [noun]. He is very spotty [adjective]") and ten required an inflectional morpheme (i.e. a morpheme that indicates change in tense or number; e.g. "This boy loves to ski. He says nothing is as much fun as skiing.”). Scores out of 20 for each test were obtained along with scores out of ten for the derivational and inflectional changes separately.

Past tense production

A specific type of inflectional morphology was examined, namely, past tense production. Twenty sentence pairs (K. Patterson, personal communication) were read to each participant. The participant heard the first sentence of each pair, which was in the present (habitual) tense, and the start of the second sentence, which began "Yesterday ...". The participant was required to complete this sentence in the past tense using the verb that was presented in the first sentence. If necessary they were given an example before the test ("Every day I wash my hands. Yesterday 1 washed

my hands"). Ten of the sentences required construction of regular past tense (e.g. walk - walked) and ten required an irregular past tense form (e.g. teach - taught). Each response was scored as correct or incorrect to obtain a maximum score of 20 for the whole test and two scores out of ten for the regular and irregular verbs.

Nonword Reading and Spelling

Thirty monosyllabic pronounceable nonwords were presented one at a time, on cards for reading. Correct responses were scored out of 30.

Thirty monosyllabic nonwords were presented by the examiner one at a time for written spelling. These were scored as correct if the written form corresponded to the written form of the nonword that was used in the test or to a possible homophone, (e.g. reat or reet, are acceptable spellings of the same nonword).

Praxis

Limb

Limb praxis was assessed using a rating scale for fifteen simple movements of the arms. Movements were meaningful (e.g. combing hair), meaningless (e.g. making a circle in the air) or demonstrated the use of an object (e.g. a key). Each movement was rated on a scale from zero to three points: zero for no movement or an incorrect movement, one point for an attempt at the correct movement but poor execution, two points for a correct movement with minor problems in execution, and three points for a correct execution of the movement required. Therefore a maximum score of 45 was possible for this test.

Orofacial

Orofacial praxis was assessed using a rating scale for movements of the oral and facial musculature. Twenty-nine single movements and three sequences of movements were assessed. Items required meaningful noise production (e.g. the noise a dog makes; six items), meaningless noise production (e.g. clicking the tongue; five items), singing (e.g. sing Happy Birthday; four items), nonvocal movements (e.g. biting the bottom Hp; ten items), eye movements (e.g. closing the left eye; four items) and sequences of three movements (e.g. blowing up the cheeks, then ticking the tips, then smacking the tips). If the movement was not executed perfectly following the verbal command, then it was demonstrated by the examiner and the imitation of the movement was scored according to the rating scale from zero to three as described above. The maximum score possible for this test was 96.