She found that milestone achievement was abnormal in these monkeys: at six to eight
weeks they were slow in starting to manipulate, and at ten months the increase in «motor disturbance
behaviors» that normally occurs was prolonged.101 The author concludes, «These effects could occur as a result of effects on vulnerable brain processes
during a sensitive period, interference with programming of [normal] brain development by endogenous [internal] agents or alteration in
early experiences.»