Fifty Brazilian scientists working in life sciences were interviewed i
n order to explore reasons of bursts and falls in their scientific pro
ductivity. Scientists recognize specific periods of time of their care
er during which they are more productive. Bursts of productivity are i
nfluenced mainly by human relationships and, to a lower extent, by mat
erial conditions (equipment, grants, etc), time dedicated to work and
reasons linked to the kind of work carried out. The most productive sc
ientists tend to attribute more importance to human relations than the
ir colleagues with lower productivity scores. Some possible reasons fo
r this discrepancy are discussed.