Teenagers respond to emails on average within 13 minutes whereas 51 year olds take an average of 47 minutes to hit reply, according to a new study from researchers at the USC Viterbi School of Engineering. The group researched the factors that influence how people respond to emails in order to identify who is most likely to respond to emails the fastest. Gender didn't have a major influence on how quickly someone responded, but device did. A laptop users takes about twice as long as a mobile phone user to respond to an email.