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Worth a Thousand Words

The New Oxford American Dictionary’s Word of the Year for 2009, unfriend, has prompted much debate online as to whether the chosen word should really have been defriend instead. Either way, both unfriend and defriend are examples of a word’s meaning being changed through the addition of an affix; in this case, unfriend (and defriend) both mean “to remove someone as a friend on a social networking site.”

This week’s PLoS ONE featured content also involves affixation—but this time in the alarm calls made by male Campbell’s monkeys (Cercopithecus campbelli), the meanings of which, according to Karim Ouattara and colleagues, can be altered through the addition of affixes. The findings are published in an article entitled, Campbell’s Monkeys Use Affixation to Alter Call Meaning.

Ouattara and colleagues found six different types of alarm call made by Campbell’s monkeys, each of which consisted of an acoustically variable stem, which can be followed by an acoustically invariable suffix that alters the meaning of the stem. Continuing the human language analogy, in English, the verb jump has a different sound pattern to the verb kiss but adding the suffix -ed changes the meaning of both verbs in a consistent way (i.e. it puts them into the past tense).

The researchers collected the data both from opportunistic observations in the wild and from field experiments in which visual and auditory stimuli were presented to the monkeys. Based on their findings, they concluded that, “when referring to specific external events, non-human primates can generate meaningful acoustic variation during call production that is functionally equivalent to suffixation in human language.”

The featured audio files form Audio S1 and Audio S2 from the supporting information section of the published paper. S1 represents a “hok” call—associated with the presence of a crowned eagle—while in S2, you can hear a “hok-oo” call, which are made in the context of a range of disturbances, including the presence of eagles, neighbouring groups and, more rarely, a flying squirrel.

If you enjoyed reading this paper, you may also like to browse the other articles in the PLoS ONE evolutionary biology section. To receive notifications of new PLoS ONE articles, why not sign up for our eTOCs or one of our RSS feeds.

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