A study by Portuguese scientists looked at coffee drinkers to understand whether the effects of caffeine caused the wakefulness effect or whether it was more about the experience of drinking the beverage.

Researchers recruited people who often drank a minimum of one cup of coffee per day and asked them to refrain from eating or drinking anything with caffeine in it for at least three hours.

Participants then underwent MRI (magnetic resonance imaging) scans, one before and one 30 minutes after either consuming a cup of coffee or another caffeinated product.

During the scan, participants were told to relax and allow their minds to wander.

The team of scientists expected the functional MRI scans to show the people who drank coffee having a higher integration of networks that are linked to the prefrontal cortex - associated with executive memory - and the default mode network (DMN), which is associated with introspection and self-reflection processes.

However, instead, they found the connectivity of the default mode network was decreased both after drinking coffee or taking another form of caffeine.

Scientists say it indicates that consuming either caffeine or a cup of coffee made people more prepared to move from "resting" to "working" on tasks.

But the study also revealed that drinking coffee increased connectivity with parts of the brain which are involved in working memory, cognitive control, and goal-directed behaviour.

This did not happen when participants took other caffeinated products.

The experts said experiencing a cup of coffee was key to raising the feeling of alertness and making the drinker "ready to go".

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Dr Maria Picó-Pérez, an author of the study, said: "In simple words, the subjects were more ready for action and alert to external stimuli after having coffee.

"Taking into account that some of the effects that we found were reproduced by caffeine, we could expect other caffeinated drinks to share some of the effects.

"However, others were specific for coffee drinking, driven by factors such as the particular smell and taste of the drink, or the psychological expectation associated with consuming that drink."

The authors of the study said that it was possible the experience of drinking coffee without caffeine could also cause these benefits.

This study could not differentiate the effects of the experience alone from the experience combined with the caffeine.

There is also a theory that the benefits coffee drinkers claim could be due to the relief of withdrawal symptoms, which this study did not test.

Professor Nuno Sousa, of the University of Minho, added: "The changes in connectivity were studied during a resting-state sequence. Any association with psychological and cognitive processes is interpreted based on the common function ascribed to the regions and networks found, but it was not directly tested.

"Moreover, there could be individual differences in the metabolism of caffeine among participants that would be interesting to explore in the future."