For anyone who needs a morning cup of coffee to function like a human being, your favourite morning routine might actually be taking the pep out of your step. A new book by Cambridge psychologist Brian Little found that your personality type can predict whether drinking coffee will help or hurt your day’s productivity. According to the study published in Me, Myself, and Us: The Science of Personality and the Art of Well-Being, introverts should be stepping away from their morning cup of coffee. Little examined the personalities of coffee drinkers and found that after two cups of coffee, extroverts carry out tasks more efficiently, whereas introverts perform less well. This performance suffered more if the task was quantitative and was being carried out under time pressure. This meant that in high pressure situations, especially where there was issues such as data analysis or budgeting talk, introverts’ efficiency while extroverts were seen to benefit from the coffee – giving them an advantage in the meeting. Little went on to suggest to New York Magazine, that introverts are naturally overstimulated by their environment, while extraverts are under the optimal level of stimulation. What this really means is that caffeine, and any other stimulant, can make introverts feel overwhelmed in stressful situations. If you’re a coffee devotee who can’t quit her cuppa, Little suggests having it later in the day, and avoiding before any high-pressure situations.