Communication and information scientist of the Netherlands Organization for Scientific Research, Karien Coppens, monitored the development of vocabulary in 140 deaf and severely hearing impaired pupils for a period of one to four years. The children were between 8 and 13 years old at the start of her research. Every time they were assessed, the children were presented with two assignments that measured both the extent to which they were able to recognize words and their deeper vocabulary.
Coppens compared the results with those of 819 primary school children without hearing impairment. The researcher established that the size, depth and growth of vocabulary in children with hearing impairment are less than that of hearing children. The weakness is the greatest when it comes to difficult words.
To distinguish between difficult and easy words, Coppens conducted a statistical analysis of the most frequently occurring words in the Dutch aptitude test administered at the end of primary school. The groups of words differed from each other by the number of letters, the age at which the child learns the word, how easily the word can be conceptualized, and frequency of use. Children with a hearing impairment performed least well compared to hearing children when faced with words from the group of difficult words.
As a possible explanation Coppens said, "In general, deaf children develop a smaller basic vocabulary because they take in fewer words indirectly from their surroundings compared to hearing children."
Hearing impaired children, incidentally, exhibit wide individual differences in their reading vocabulary. Coppens said, "Children who wear a hearing aid or have a cochlear implant, children who are highly intelligent, who communicate with their parents through speech, who go to ordinary schools or in whom hearing impairment has occurred later in life have an advantage here."
It is striking that the differences in performance between hearing impaired children remain the same over time. Having a relatively large vocabulary now also means they will have a relatively large vocabulary in later life. The same is true for children with a relatively small vocabulary.
Due to an Added Value grant from NWO, Coppens' scientific insights can be put into practice. "We have developed a 10-minute vocabulary test that teachers can administer to children electronically," said Coppens. "This test, for instance, helps to clarify whether a hearing impaired pupil has a vocabulary of a sufficient level to enable him or her to transfer to an ordinary school," said Coppens.
The test, called Woord voor Woord (Word for Word) has nine levels. Every time the test is taken, the degree of difficulty changes automatically on the basis of the results the child achieved previously. Expectations are that schools for children with hearing impairment will be able to make use of Woord voor Woord from next year onwards.