Coffee cravings can play havoc with your memory

Skipping your morning coffee before a lecture or an important meeting is probably a bad idea, according to new research. Of course you will be less alert, but more than that, the research team at the University of Tasmania say that the cravings you experience will impair your ability to memorise new information. Reporting their results in the journal Memory, the researchers also found that their participants were unaware of how caffeine cravings had affected them – suggesting that if we try to learn things when desperate for a coffee we are at risk of being overconfident about what we've taken in.

The participants were 55 regular coffee drinkers (average age 30 years) who drank at least one coffee per day and who at least sometimes found themselves thinking about when they will get their next caffeine fix (another 11 participants were excluded because they didn't describe experiencing these feelings often enough).

The memory challenge was to learn 100 unrelated word pairs, such as POND-BOOK. Following this, the participants were tested on their ability to recall the second word in each pair (given the first word). They were also tested on their recognition memory, which involved selecting the correct second word for each pair from a multiple-choice list of options.

Most important, before the memory challenges began, half the participants were placed in a state of craving. They'd been asked to refrain from any coffee that day, and then they were teased cruelly with a cafetière of coffee, which they poured into a cup, but were not allowed to drink. They were also encouraged to pay attention to the smell and colour of the drink. The other participants acted as controls – they drank coffee as usual earlier that day, and they poured themselves a jug of water and imagined their favourite holiday (this was to give them a task that was fairly similar to the craving induction).

The control participants significantly outperformed the caffeine craving participants on both recall and recognition memory. "Cravings trigger consumption schemas and the inhibition of these schemas requires cognitive resources, leaving fewer resources available for other cognitive tasks," the researchers said.

Another detail is that the participants had been asked to estimate how well they thought they would do at the two kinds of memory test. The judgments of the caffeine craving participants were adversely affected – they were less able to judge the accuracy of their answers than the control participants and this meant they were more overconfident in their upcoming performance.

A weakness of the study is that there was no baseline control group of non-coffee drinkers, who were not craving coffee but also hadn't had the benefit of coffee. This means it's possible the results can be explained by coffee's memory enhancing effects, rather than coffee craving having detrimental effects. However, Matthew Palmer and his colleagues who conducted the research think this is unlikely since findings for caffeine having memory enhancing effects have been mixed.