The importance of non-verbal skills in the acquisition of place-value knowledge: Evidence from normally-developing and language-impaired children

Children's comprehension of the Hindu-Arabic number system was explored in relation to their ability to match spoken to Hindu-Arabic numerals. The pos sible involvement of verbal processes in numeric understanding was examined by comparing a group of 8-year olds with specific language impairments (SL I group, N = 13) to Mo control groups, the first matched for age and non-ve rbal ability (AC group, N = 13), the second younger group marched for langu age comprehension level (LC group, N = 12). SLI, AC and LC children's accuracy and efficiency in choosing the greater o f two single-digit Hindu-Arabic numerals were compared. One child from the SLI group and three from the LC group failed to reach accuracy criterion. F or accurate responders there was no difference between SLI and AC groups in latency ro judge: both responded faster than the LC group. When making jud gments all groups showed the Symbolic Distance Effect observed by Moyer & L andauer (1967). All participants mere able to match spoken numerals to Hind u-Arabic single-digit numerals without error. SLI and AC groups were tested on double digits. Accuracy and efficiency in judging the greater of two Hindu-Arabic double-digit numerals were rested. Ability to match spoken numerals to corresponding double-digit Hindu-Arabic numerals was also tested. All of 12 AC participants accurately matched spo ken to Hindu-Arabic symbols, but 2 of these were unable to judge accurately the greater of pairs of Hindu-Arabic symbols. Of 13 SLI children tested, 9 accurately matched spoken to Hindu-Arabic symbols; 2 of these were unable to judge Hindu-Arabic symbols accurately. One further child was able to jud ge accurately but performed poorly when matching spoken to Hindu-Arabic num erals. When school experience of double-digit numbers was statistically con trolled, there was no difference between SLI and AC groups in the accuracy of double-digit judgments. No difference was found between SLI and AC group s in the speed or pattern of accurate responders' double-digit judgments. W hen group data was pooled and school experience statistically controlled, a ccuracy in double-digit judgment was predicted by non-verbal ability, but n ot by expressive or receptive language skills. The pattern of responses to the double-digit judgments suggested a 'holisti c' processing mechanism within which 'transparent' stimuli (chose double di gits which minimize conflict between 'face' and 'place' values) are most ra pidly encoded. Whereas the ability to match verbal labels to Hindu-Arabic numerals appears generally to precede single- and double-digit comprehension, findings sugg est: that, especially in the acquisition of place-value knowledge, there is substantial autonomy of non-verbal systems.