A wide variety of hypotheses have been put forth that address the func
tional significance of active sleep. Despite the well-accepted fact th
at active sleep expresses itself predominantly in the perinatal period
, the vast majority of these functional hypotheses are applicable larg
ely, if not exclusively, to the adult. We build on the developmental a
pproaches of previous researchers and propose that the individual comp
onents of active sleep (e.g., myoclonic twitches, rapid eye movements)
exhibit unique developmental and phylogenetic histories and may serve
independent functions in the developing organism. This dynamic perspe
ctive leads to specific experimental approaches aimed at the developme
ntal roles of these components in the neonate, their maintenance roles
in the adult, and the means by which these various components coalesc
e temporally in what is commonly referred to as a behavioral state. (C
) 1996 John Wiley & Sons, Inc.