Eating lunch alone in your office may not sound like fun, but it could increase your mental acuity later in the day, according to a new study. Researchers recruited 32 female university students in their mid-20s and divided them into two groups. Before the experiment, all volunteers filled out a questionnaire that assessed their mood. They were also given a test of reaction time where they had to identify shapes on a screen that appeared in different locations. Then participants in the first group invited a friend along for lunch at an Italian restaurant; they were allowed to choose their dish and eat leisurely for 1 hour. Those in the second group received the same meal, but they ate it alone in a small office room and were given just 20 minutes to finish. After the meals, the volunteers completed another mood questionnaire and repeated the reaction-time test. Students who leisurely ate lunch at a restaurant with company were calmer than those who ate alone in an office, researchers report online today in PLOS ONE. But restaurant diners did not improve on the reaction-time test after their meal, whereas those who ate in an office were about 40% faster after their meal. The team suggests that eating lunch at a restaurant with friends may put you in a relaxed mood and stop you from closely monitoring your actions for errors.