Bibliographic Citation
Nash, H. & Snowling, M. (2008). Semantic and phonological fluency in children with Down syndrome: Atypical organization of language or less
efficient retrieval strategies? Cognitive Neuropsychology, 25 (5), 690-703.
Summary
An interesting study by Hannah Nash and Margaret Snowling, featured in the British journal Cognitive Neuropsychology, compares semantic and phonological fluency in typically developing children and children with Down syndrome. The authors build on previous research on the cognitive deficits displayed by students with Down syndrome in reading and vocabulary memory tasks, with the primary goal of highlighting specific causes for the lack of productivity in these children.
For children with Down syndrome (DS), overall vocabulary knowledge is fairly typical, but brain activity required for word retrieval and attention load is hindered. The authors note that among typically developing (TD) children and adults, phonological fluency is always lower than semantic fluency because of the heavy reliance on executive functions in the brain. The same holds true for DS students, but to a greater extent. Previous brain research reveals that children with DS show similarities to patients with frontal lobe lesions and Parkinson’s disease, who have normal semantic fluency but impaired phonological fluency (p. 692).
For their particular study, Nash and Snowling compared the results of semantic and phonological tasks between TD and DS students. They predicted that DS children would score higher on the semantic task than the phonological task, but demonstrate lower overall productivity than TD children in both tasks. They also predicted that DS students would produce fewer semantic and phonological clusters than TD children. The authors define a semantic cluster as “two or more successive words belonging to a conventional subcategory” (p. 697). Subcategories for animals included mammals (divided into wild, domestic, and farm), amphibians, and birds; while food subcategories included meats, fruits, and vegetables. Phonological clusters were more complicated, in that they were broken down into several combinations of consonant-vowel placements within words.
Thirty-four children in all participated in the study. There were 17 children with DS, 7 males and 10 females, and 17 TD children, 6 males and 11 females. The average age of the DS children was 14 years, while the average age of the TD children was 7 years. All of the students were tested individually at their respective schools, in a room that was strictly controlled for a proper testing environment. The students’ responses were recorded digitally and by hand. The semantic task was done first. Students were given 60 seconds to name as many animals and foods (in two separate instances) as possible. The experimenter told the students, “I want you to tell me as many different kinds of animals/foods as you can think of, as fast as you can. Go” (p. 694). The phonological task tested for initial phoneme fluency. Following the same protocol as the semantic task, students were told to name as many words that start with a ‘t’ and ‘b’, respectively, as fast as they could. The children had 60 seconds to complete this task as well.
Results
The results for the semantic task confirmed the authors’ predictions regarding productivity (number of correct responses) and clustering. The TD students performed better than the DS students on the animal and food tasks, and said more clusters for each category, although cluster size was not significantly larger for this group of children. This means that the TD students more often named clusters of words (like insects for the animal category) but when the students with DS did say clusters, those clusters contained just as many words. I believe that the DS students said less clusters because of deficits in the categorization of concepts rather than a lack of general knowledge, especially considering that both groups produced very few errors. This could explain why their responses were more “random” than TD students’ responses.
Phonological task results also confirmed predictions made by Nash and Snowling, the main one being that students with DS had higher production for the semantic task than the phonological task. Once again, TD students’ overall production was higher, as was the amount of clusters. Both groups of students performed better with naming words starting with ‘b’ rather than ‘t,’ although no substantial conclusions could be made from this information. The cluster size for ‘t’ words was barely larger for students with DS, and vice versa with ‘b’ word clusters. It is worthy to note that the only students to produce nonwords were the TD children. I believe this could be caused by these students guessing more, and attempting to produce more words by overreaching, whereas students with DS may have been limited to only what vocabulary they already possessed. This is just speculation on my part.
The authors made some thought-provoking points in the Discussion section of their study, especially in regards to the possible reasons for the DS students’ lower fluency production on the semantic and phonological tasks. As for these possible causes, Nash and Snowling state:
“In principle, this lower productivity could be the result of their knowing fewer exemplars within each category or subcategory,
having poorly organized word knowledge, being slower to produce responses (as a result of articulation difficulties and/or
slower speech rate), or having inefficient word retrieval strategies" (p. 701).
But immediately, they begin to rule out certain possibilities, one of which being an “impoverished lexical content” (p. 701). As I speculated earlier, DS students do not necessarily possess a smaller knowledge base, although I was wrong about them having categorization deficits. Nash and Snowling say that “linguistic knowledge was organized similarly in the two groups of children” and in DS students there was “evidence of clustering according to context” (p. 701). So the only remaining reasons for their problems with semantic and phonological fluency are slower responses and retrieval deficits.
This study did not directly test articulation and speech rate, so it is hard to determine if those are causing fluency problems. The authors note that if slower speech rate was the reason, cluster size would be affected along with the number of clusters; but as was mentioned earlier, this did not happen. DS students’ clusters were for the most part just as large as their TD counterparts. Thus, that leaves inefficient word retrieval as the sole source of the lack of production. According to Nash and Snowling, less efficient retrieval strategies are more likely to be causes of lower production on fluency tasks than deficits in semantic and phonological organization (p. 702). Also, it appears that students with DS have fairly typical linguistic representations. Therefore “this study produced little evidence of atypical or disordered language among children with Down syndrome… the findings suggest that these children may have executive deficits that affect word retrieval processes” (p. 702).
Implications for Special Education
This study can serve as helpful information for Special Education instructors who wish to develop phonemic awareness and vocabulary knowledge in children with Down syndrome, as well as other students who have learning disabilities or intellectual deficits. First, the authors’ research findings are useful for elementary classrooms because they give a neuropsychological basis for determining areas in literacy in which children may struggle. It is important to note that across the intelligence spectrum, executive functions are taxed more with phonological tasks than with semantic tasks.
Teachers should be aware of this fact when dealing with phonemic isolation and when initiating activities that have the student attempt to substitute middle and ending phonemes in words. Although an overemphasis on phonemic awareness can become detrimental to whole word fluency, it is vital nonetheless for teachers to be patient and allow students to focus on processing phonemic information fully. Whole word automaticity will be achieved easier once a solid phonological foundation is established; vocabulary instruction should also progress faster as a result.
The results of Nash’s and Snowling’s experiments with semantic and phonological fluency can aid Special Education teachers in reading instruction with students with Down syndrome. It should be encouraging that this population demonstrated a fairly typical range of vocabulary for animal and food categories and said clusters of words close to the size of their typically developing counterparts. Exposing them to a wide variety of topics and vocabulary words will allow them to continue to thrive in semantic fluency. Teachers of students with Down syndrome need to focus on helping them improve their word retrieval strategies, as well as push for more brain-based research in the literacy field. Even with all the setbacks these children face academically, students with Down syndrome can achieve much success if they are competent readers. As the authors note in their conclusion, more research is needed to find effective strategies to help reading instructors of exceptional children.
Critique
This study by Hannah Nash and Margaret Snowling was chock full of fascinating research on semantic and phonological fluency. The fact that it was written from a neuropsychological perspective gave this article more reliability in my mind. All too often, educational methods are not adequately backed by solid brain research, so it was satisfying in that regard. Unfortunately, this also contributed to an overabundance of statistical and academic jargon, which makes it difficult for the average reader to understand.
The authors’ experiments with semantic and phonological tasks were explained in detail; it is apparent that they planned and executed the study with precision. I also liked the manner in which they considered and ruled out possible reasons for the DS group’s lower fluency scores. It was helpful as a pre-service teacher to see each possibility covered in such a methodical manner. Although the results of their study yielded few new answers on the topic, it certainly confirmed previous research and will hopefully encourage further studies into literacy topics for special populations of students. “Semantic and phonological fluency in children with Down syndrome: Atypical organization of language or less efficient retrieval strategies?” is recommended for pre-service teachers going into special education, and to primary reading instructors who don’t mind sifting through some heavy statistical terminology.
