TY - JOUR TI - Poor coherence in older people's speech is explained by impaired semantic and executive processes AU - Hoffman, Paul AU - Loginova, Ekaterina AU - Russell, Asatta A2 - Jefferies, Elizabeth A2 - Behrens, Timothy E A2 - Taylor, Jason A2 - Turner, Gary VL - 7 PY - 2018 DA - 2018/09/04 SP - e38907 C1 - eLife 2018;7:e38907 DO - 10.7554/eLife.38907 UR - https://doi.org/10.7554/eLife.38907 AB - The ability to speak coherently is essential for effective communication but declines with age: older people more frequently produce tangential, off-topic speech. The cognitive factors underpinning this decline are poorly understood. We predicted that maintaining coherence relies on effective regulation of activated semantic knowledge about the world, and particularly on the selection of currently relevant semantic representations to drive speech production. To test this, we collected 840 speech samples along with measures of executive and semantic ability from 60 young and older adults, using a novel computational method to quantify coherence. Semantic selection ability predicted coherence, as did level of semantic knowledge and a measure of domain-general executive ability. These factors fully accounted for the age-related coherence deficit. Our results indicate that maintaining coherence in speech becomes more challenging as people age because they accumulate more knowledge but are less able to effectively regulate how it is activated and used. KW - language KW - executive control KW - knowledge JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -