Communication Accommodation Theory (CAT), developed by Howard Giles from the 1970s onward, explains why people modify their communicative behavior — speech rate, vocabulary level, accent, register, and even non-verbal cues — during interaction. The central claim is that these adjustments are not random or purely subconscious, but are driven by social motives: the desire for approval, the marking of group identity, or the negotiation of power relationships.

Convergence and Divergence

The two primary processes in CAT are:

Convergence: Adapting your speech toward your interlocutor’s style to signal affiliation, approval-seeking, or solidarity. Examples:

• Slowing down speech when talking to a non-native speaker
• Shifting accent or dialect to match a conversational partner
• Adopting the jargon of a group you wish to be accepted by

Divergence: Adapting away from the interlocutor’s speech to assert distinctiveness or mark group boundaries. Examples:

• A Welsh speaker increasing Welsh accent features when speaking with an Anglo-English interlocutor seen as threatening to Welsh identity
• A speaker shifting to more formal register to signal professional distance

Both processes are partially conscious and partially subconscious.

Over-Accommodation

CAT also accounts for over-accommodation — adapting too much in ways that are perceived as condescending:

• Speaking very slowly and loudly to an elderly person
• Excessive simplification of vocabulary with a non-native speaker

Over-accommodation often backfires and signals disrespect.

CAT and Second Language Acquisition

CAT is relevant to SLA in several ways:

• Input modification: native speakers often converge to learners by simplifying vocabulary, slowing speech, and avoiding idioms — this has been studied as foreigner talk
• Identity and divergence: learners who face pressure to assimilate may diverge linguistically as an act of resistance
• Accent acquisition: willingness to accommodate phonologically influences how nativelike learner pronunciation becomes
• Classroom interaction: teacher accommodation patterns affect how learners engage

Related Terms

• Convergence: Moving speech style toward the interlocutor
• Divergence: Moving speech style away from the interlocutor
• Foreigner Talk: The simplified speech native speakers use with learners
• Identity: How language relates to personal and group identity
• Interactional Sociolinguistics: Broader framework including accommodation