How early in life does temperament appear?
Babies who are very active before they are born are likely to keep moving after birth. Maternity room nurses can often identify the "active, loud babies" from the first day.
At birth, temperament can be clouded by prematurity, birth hormones, the after-effects of a difficult birth, unfinished neurological development, or colic. For this reason, we recommend parents wait until 4-6 months to fill out the first temperament questionnaire.
Not all temperament traits show up early on. Some appear over time, just as different colored flowers gradually appear on different plants. For example, "persistence" is difficult to see until a baby begins to develop skills (rolling over, sitting up, crawling, etc.). Only then are parents likely to notice how much a baby practices each skill. Busy toddlers are not known for attention span, so we don't measure that trait until the preschool years.