Knowing which tense to use when talking about other people's work is also important. You need to consider actual research events as taking place in the past, but conclusions and generalisations extracted from that research are part of our ongoing general knowledge and can be referred to in the present. This can be represented on a timeline, eg:
This can also be demonstrated by contrasting the following two sentences:
i) the present tense to imply that the information is 'generally' accepted, eg:
'According to Smith (1993) adolescent substance abuse is highest in cities'
(present tense - a generally accepted fact – part of current ongoing knowledge)
ii) the past tense to present the information as specific example of research, eg:
'According to Smith (1993) adolescent substance abuse was highest in cities'
(past tense - the results of specific research which may have been superseded)
