  In this paper, we study a sample of 65 short duration bursts contained in the
3B catalogue. We fit the time profiles of these GRBs with lognormal functions
and study various temporal properties.
  In most of the multi-peaked bursts, our analysis leads to a statistical
evidence for the evolution of temporal asymmetry in individual pulses i.e.
subsequent pulses in a GRB, on an average, tend to be more symmetric. Using a
peak asymmetry evolution parameter, we find that 90% of short duration GRBs
with 3 or more peaks exhibit the above trend individually.
