  Words follow the law of brevity, i.e. more frequent words tend to be shorter.
From a statistical point of view, this qualitative definition of the law states
that word length and word frequency are negatively correlated. Here the recent
finding of patterning consistent with the law of brevity in Formosan macaque
vocal communication (Semple et al., 2010) is revisited. It is shown that the
negative correlation between mean duration and frequency of use in the
vocalizations of Formosan macaques is not an artifact of the use of a mean
duration for each call type instead of the customary 'word' length of studies
of the law in human language. The key point demonstrated is that the total
duration of calls of a particular type increases with the number of calls of
that type. The finding of the law of brevity in the vocalizations of these
macaques therefore defies a trivial explanation.
