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THE LINGUISTICS STUDENT’S HANDBOOK 62
fild/, we can see that we have two markers of the past tense which we are able
to distinguish, namely /t/ and /d/. But we also need to know whether the two
contrast. To discover this we can do a commutation test, sometimes called a
substitution test.
In a commutation test we ask whether replacing one element in the analysis
with another leads to a change on another level of analysis, specifically on the
semantic level (this is the equivalent to asking whether this is important for the
rules of the game in the Ludo analogy). So if we take the analysed final /t/s
from the sets provided above and replace them with /d/s, do we get to a regularly
different meaning? The answer is ‘no: we get impossible combinations:
/*dju�pd, *lɑ�fd, *lυkd, *wɔ�kd/’.
We can compare this with what happens when we put an /iŋ/ in place of the
/t/. Then we get /dju�piŋ, lɑ�fiŋ, lυkiŋ, wɔ�kiŋ/, each of which is an occurring
word, but one which does not mean the same as the original word. By this
method we discover that /iŋ/ and /t/ contrast in this position. We can also
discover that each is associated with its own meaning, and that the contrast is
not restricted to the particular examples we have chosen here, but is very
general when we add these different endings to a verb stem.
A pair of words like /dju�pt/ and /dju�piŋ/ differ in just one element and
mean different things, and we talk of a minimal pair. A minimal pair is proof
of contrast. It is the result of a commutation test having shown that contrasting
elements are involved. Note that the ‘elements’ being discussed here are
elements at the relevant level of analysis. The fact that /iŋ/ is made up of two
speech sounds is irrelevant, because neither of those two sounds carries a
meaning on its own.
So contrast is more than just being able to tell that two things are different;
contrast implies functioning within the system to provide different messages.
The same notion of contrast can be used within phonology and syntax. In
phonology, minimal pairs such as [tik] and [tυk] show that [i] and [υ] contrast
in English, because tick and took do not mean the same. On the other hand,
although we can hear the difference between [�] and [l], when they occur in
words like plead [p�i�d] and bleed [bli�d] in English we cannot use them to distinguish
meanings, and so they do not contrast. They may contrast in other
languages, but they do not contrast in English.
In syntax, pairs of sentences such as I love my wife and I love your wife equally
provide minimal pairs which prove the contrast between my and your, but
which equally prove the parallel function of the two. Minimal pairs are more
often used in syntax for this second reason. For example, the fact that you can
substitute it for the underlined section in The weather we have been having all
this month has been awful shows that the two have parallel function. We could
have said the same for [i] and [υ] in tick and took, where both have the same
function in the syllables in which they occur.