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At what stage in the drinking process does drinking water affect attention and memory? Effects of mouth rinsing and mouth drying in adults


Drinking water is important for health and there is an agreement that drinking water facilitates certain cognitive processes. However, the mechanism underlying the effect of drinking water on cognition is unknown. While attention performance is improved by even a very small drink, memory performance seems to require larger drinks for performance enhancement. This suggests that attention could be affected earlier in the drinking process than memory. We aimed to elucidate further the mechanism involved by investigating the stage during the drinking process influencing performance on cognitive tasks. To this end, we compared mouth rinsing and mouth drying. Mouth rinsing was expected to result in improved attention performance and would suggest that the mechanism responsible is located in the mouth and occurs early in the drinking process, before swallowing. Eighty-seven adults participated in either a treatment (mouth rinsing or mouth drying) or control (no intervention) condition. They were assessed at baseline and 20 min later after intervention on measures of visual attention, short-term memory, subjective thirst and mood. Our results showed that mouth rinsing improved visual attention, but not short-term memory, mood or subjective thirst. Mouth drying did not affect performance. Our results support the hypothesis that different mechanisms underlie the effect of drinking water on different cognitive processes. They suggest that merely sipping water, as opposed to having a large drink, can improve attention.

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This research did not receive any specific grant from funding sources in the public, commercial or not-for-profit sectors. This work was part funded by money given to the first author by Nestec for an unrelated project—they had no influence in instigating, designing, analysing, interpreting or submitting the paper.

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Correspondence to Caroline J. Edmonds.

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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. All procedures were approved by the Department of Psychology ethics committee, University of Westminster (ETH1617-0099) and the University of East London ethics committee (UREC 1516 74).

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Edmonds, C.J., Skeete, J., Klamerus, E. et al. At what stage in the drinking process does drinking water affect attention and memory? Effects of mouth rinsing and mouth drying in adults. Psychological Research 85, 214–222 (2021).

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