When people are
asked to supply as many meanings as they can for a word presented orally and
out of context, they begin with the most frequent meanings, and once these are
exhausted, turn to other, less common, meanings. This process requires a strategic search in
the knowledge base and mental flexibility, which are part of executive
functions.
The homophone
meaning generation test – HMGT , developed in Hebrew by Prof. Gitit Kave and
her colleagues, tests this
process. Homophones are words which have
different meanings that "sound the same". For instance, the word "right" has
the meaning of "a direction (opposed to "left")" and the
meaning of "appropriate, suitable".
The test in its
Hebrew form is made of 24 homophones, each having between three and ten
possible meanings. Half of the words are
also homographs (all their meanings are spelled the same way).
The words are presented orally, one by one. The person is asked to think about as many
meanings as he can to each word. There
is no time limit. When the person is not
able to think about any more meanings, the next word is presented. Each different meaning is assigned a
point. The score in the test is the
number of meanings given to all presented words. The production of meanings requires strategic
search and mental flexibility, thus the test is supposed to measure executive
functions.
Prof. Kave and her
colleagues performed a few experiments with this test, in children and adults,
two of them will be presented here,
In the adult study,
the relation between the homophone test and shifting and clustering in fluency
tests was examined.
What are shifting
and clustering?
Phonemic fluency
tests (in which the person is asked to name as many words beginning with a
specific letter within one minute as he can) and semantic fluency tests (in
which a person is asked to say as many words belonging to a specific category
within one minute as he can) measure the ability to search and retrieve
information from long term memory (thus they belong to the broad ability "Long
Term Storage and Retrieval").
In both of these
tests, the memory search includes two aspects:
clusters and switches. During
test performance people usually produce clusters of words that are related to
each other semantically (for instance, "horse, cow, donkey, goat, sheep"
is a cluster of "farm animals") or phonetically (for example, "buy,
bug, bus" is a cluster of words beginning with "bu"). When the subcategory from which the words
were retrieved is exhausted (the person cannot think about more farm animals or
more words beginning with "bu"), the person shifts to another
subcategory (for instance, he will transfer to "sea animals" or to "be").
Clusters reflect the semantic organization of the
crystallized knowledge. Shifts reflect
executive functions (strategic search in the fund of lexical knowledge,
monitoring, the initiation of response, flexibility, an ability to shift set).
The phonemic fluency
test is presumed to require executive functions more than the semantic fluency
test. This is because when we retrieve
information by content (like in the semantic fluency test) we perform a
familiar act which fits the way our knowledge is organized. But when we retrieve words beginning with a
specific letter, we perform a new and unfamiliar task. In order to optimally perform this task we
have to come up with a search strategy, monitor the search process and act
flexibly. These are executive functions.
One hundred
volunteers aged 18-35 and with an average of 13.8 years of education participated in the study. All participants were healthy native Hebrew
speakers. Each participant was tested
with the homophone test and the semantic and phonemic fluency tests.
Since the homophone
test was built as an executive functioning test, requiring directed and flexible
memory search, the assumption was that the homophone test will be correlated
with phonemic fluency more than with semantic fluency. In fact, a significant and equal correlation
was found between the homophone test and both fluency tests.
The authors offer 2
kinds of explanations for this finding:
it may be that the lexical knowledge component existing in the homophone
test and the semantic fluency test caused the correlation between these tests
to be higher than expected. Another
possibility is that both fluency tests require a similar executive search. The relation between all three tests can be resulting
from a common executive component, which is necessary for successful
performance in these tasks.
When
we look at the shifts and clusters data we get a finer picture:
Performance in the homophone test was related more to
the number of switches or the number of clusters that a person
performed in both fluency tests, than to the average size of the cluster
in these tests. This strengthens the hypothesis,
that the relation between the three tests is stronger in the executive
component than in the lexical semantic component. While members in a sematic cluster (for
example, "dog, cat, hare, gerbil") belong to a
similar conceptual field, this is not the case with homophone representations. Thus
performance in the homophone test cannot be attributed to the spread of
activation within a sub category in the semantic lexicon
Participants in this
study produced more meanings for non-homographic homophones than for words that
are both homophones and homographs. The
score of the homographs was more strongly related to the switching component in
both fluency tests than the score on the non homographs. This means that finding different meanings
for homophones that are also homographs requires more executive functions than
finding different meanings for homophones that are not homographs.
How do children perform in the homophone test? A child cannot retrieve meanings
that do not yet exist in his lexicon. But sometimes a child will find it hard to retrieve
meanings he is familiar with since his retrieval skills may not be flexible
enough. Children's retrieval skills are
affected by the development of their vocabulary and the development of
controlled search processes in their existing lexical knowledge.
Children's
vocabulary is developing constantly, as the child is exposed to reading and literature. At the end of 2nd grade, English
speaking children's vocabulary contains 6000 word meanings. Their vocabulary increases in the next few
years at a rate of 1000 meanings per year. In addition to
the growing lexicon, knowledge about word meanings also grows. The meanings of new words are gradually refined
in a process that continues into adolescence.
Efficient search strategies also develop throughout childhood and into adolescence. These search strategies are one of
the manifestations of executive functions.
In the children's
study, changes in word retrieval throughout childhood were assessed by four
tasks: a picture naming task, a phonemic
fluency task, a semantic fluency task and the homophone test. These tasks differ in the amount of
flexibility needed to perform the test.
In the picture
naming task (in which the child sees a picture of an object and is asked to
name it) there is no need for flexibility in lexical search. Each picture corresponds to one word
only. When this word is found, the
search is over.
Semantic and
phonemic fluency tests require a more flexible search in the lexicon, using
clustering and switching strategies as was discussed earlier. There is a developmental improvement in the
performance on these tests up to the age of 12 and beyond. The fluency component that improves the most throughout childhood is
the shifting component. As was said
before, this is an executive component which reflects strategic search,
response initiation, monitoring and flexibility.
In order to perform
the homophone test optimally, the word search has to continue much after the
first word has been retrieved. Unlike
the fluency tests in which the search is performed on a limited set of the
lexical knowledge, the homophone test requires searching and retrieving from
the whole lexicon. Thus it may require a
more flexible search strategy than is required for the other tests.
Two hundred and
seven children participated in the study, 20 from each age group in the age
range of 8-17 and in grades 3rd to 12th. The children were born in Israel and speak Hebrew
as a first language. They don't have
learning disabilities, neurological or developmental problems and their
socioeconomic status is average.
The children's
scores on all four tests rose steadily between age 8 and age 17. Picture naming ability rose the least
(although the test being used was probably too easy in its Hebrew version,
since the youngest children succeeded in 83% of its items). Scores on the homophone test showed the
steepest rise. Thus, performance on the homophone test changed the
most during development.
Like the adults,
children produced less meanings for homophones that are also homographs (all
their meanings are spelled the same) than for homophones that are not
homographs. The rate of development in performance
on the homographs was identical to the rate of development in performance on non
homographs.
To summarize, this test assesses executive functions in
a verbal task. High scores on the homophone
test indicate that the person has a rich lexical network and that he is able to
shift between meanings flexibly.
How would this test be classified in CHC abilities?
I've recently written
about the place of executive functions in CHC theory – "between"
fluid ability and short term memory.
The homophone test
does not fit any of the definitions of the Fluid narrow abilities (induction, deduction,
quantitative reasoning). In Hoelzle's
study, other tests measuring executive functions are classified under fluid
ability. Hoelzle did not classify the
homophone test or similar tests. Due to the nature of this test and
the classification of other executive function tests to fluid ability, perhaps
we can classify this test also to fluid ability, at least tentatively.
The homophone test
does not fit any of the definitions of narrow abilities within Short Term Memory.
The narrow ability
"Ideational fluency" (in "Long Term Storage and Retrieval") is defined as the
"ability to rapidly produce a series of
ideas, words, or phrases related to a specific condition or object.". Because of the speed factor, the homophone
test cannot be classified here.
The narrow ability
"Lexical knowledge" (in "Comprehension - Knowledge") is
"knowledge of the definitions of
words and the concepts that underlie them". The homophone test does require such knowledge and seems to fit here.
So it seems that in CHC terms the test can be
considered to test Fluid ability and Comprehension Knowledge (Lexical Knowledge).
References:
KavÉ, G., Avraham, A., Kukulansky-Segal, D., & Herzberg,
O. (2007). How does the homophone meaning generation test associate with the
phonemic and semantic fluency tests? A quantitative and qualitative
analysis. Journal of the International Neuropsychological Society, 13(03),
424-432.
Kavé, G., Kukulansky-Segal, D., Avraham, A., Herzberg, O.,
& Landa, J. (2010). Searching for the right word: Performance on four
word-retrieval tasks across childhood. Child Neuropsychology, 16(6),
549-563.
Hoelzle, J. B. (2008). Neuropsychological assessment
and the Cattell-Horn-Carroll (CHC) cognitive abilities model. ProQuest.
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