From PhysOrg:
The caffeine in coffee is known to fight drowsiness and act as a stimulant, and previous research has suggested it might also protect against liver damage, diabetes, Alzheimer’s and inflammatory conditions such as gout. Psychologist Dr Lindsay St Claire and colleagues from Bristol University decided to find out the effects of caffeinated coffee in high stress situations such as in the work place. They divided 64 coffee-drinking volunteers into pairs of the same-sex and similar ages. They then gave them a number of tasks to complete such as memory tests, puzzles, and negotiating tasks. To increase the pressure they told the pairs they would be making a public presentation on their results. The pairs were then given decaffeinated coffee to drink, but half of them had caffeine added to their drinks. Their performance was then monitored throughout the experiments.
The aims of the experiments were to see if caffeine consumption could contribute to the experience of stress and affect performance. Since men and women are known to cope with stress differently, and this is thought to be because men tend toward a “fight or flight” response and women prefer a “tend or befriend” response, the experiment also aimed to explore women’s coping to see if this is a valid theory. The results, published in the Journal of Applied Social Psychology showed that pairs of women drinking caffeinated coffee completed puzzles 100 seconds faster than those on decaffeinated coffee, while men on caffeine completed the puzzles 20 seconds slower than those on the decaffeinated. Men drinking caffeinated coffee were “greatly impaired” in the memory tasks.
More here.