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During a conversation, each person must plan and monitor what they say to make sure it is relevant to the discussion. This is called maintaining coherence during speech. Studies suggest that as people get older they find it harder to remain coherent, and become more likely to produce irrelevant or off-topic information when speaking. This reduces how effectively they communicate and can have negative effects on their social interactions. However, little is known about how thinking skills affect coherence in speech and why this declines in later life.
To investigate, Hoffman et al. asked two groups of volunteers – a ‘younger’ group made up of people aged between 18 and 30 years old, and an ‘older’ group of people aged over 60 – to perform various speech-related tasks. For example, the volunteers were asked to speak when prompted and a computer analysis was used to evaluate how coherent they were. They also completed a speech test while distracted, and took part in tests to understand how well they can suppress irrelevant information.
The results of the tests show that three factors influence how coherent people are during conversations: how well they could control and regulate their behaviour, how much general knowledge they had, and how skilled they were at selecting the most relevant information for the task they were doing.
Having larger stores of knowledge to select from increases the challenge of staying on topic for older people. At the same time, they may experience age-related declines in the ability to suppress unnecessary information. This may help to explain why some people become less coherent as they get older and why some do not.
