Source; Adapted from Frankenburg,
INFANCY AND TODDLERHOOD
.at, her hand control becomes more and more precise. At 14 months she can aild a tower of two cubes; by 2 years she can hold and drink from a cup, and or hand preference is quite well

established; and about 3 months before her
-.hird birthday, she can copy a circle fairly well.

Locomotion
\t the age of 3 months, after a quarter year as a prisoner of gravity, Jason begins : > roll over purposefully, first from his stomach to his back and later from back to -tomach. Before this time,

however, when he lay on his stomach and rested on "is hands with his head up, he sometimes rolled over accidentally. This is why /ss and Julia never left him alone on a surface where he might roll

off.

Babies learn to sit either by raising themselves from a lying position or by •/lopping from a standing position. The average baby can sit without support Lvtween 5 and 6 months and can assume a sitting position without any help I months later.

Beginning at about 6 months, babies start to get around in a variety of ways .:nder their own steam. They wriggle on their bellies and pull their bodies along •¦¦ ith their arms, dragging their feet behind. They sometimes scoot along in a -¦.tting position, pushing forward with their arms and legs. They bear-walk, with :heir hands and feet touching the ground. And they crawl on their hands and -.nees with their trunks above and parallel to the floor. Most babies are getting : round quite well on their own by 9 to 10 months, an achievement that has nportant effects on psychological

development (see Box 5-2, page 180).

With a helping hand or the support of a piece of furniture, Jason can pull himself to a standing position just before he is 6 months old, but he onlv rarelv thieves an erect posture. At about 10 months, after some 4 months of practice pulling himself up on anything he can (and learning in the process that not.

Parents almost always show great excitement when their babies first learn to walk. The mother of this 1-year-old will soon realize how she needs to "baby-proof" her home from now on.

BOX 5-2 « THE RESEARCH WORLD
THE FAR-REACHING EFFECTS OF CRAWLING
Have you ever driven for the first time to a place where you had previously gone only as a passenger? If so, when you had to find your own way, you very probably saw landmarks you had never noticed, were aware of turns you had never felt, and—after getting there under your own steam—felt much more familiar with the entire route. The same kind of thing seems to happen to babies after they begin to get around on their own, after always having been carried or wheeled. In fact, the emergence of "self-produced locomotion" seems to be a turning point in the second half of the

first year of life, influencing many aspects of physical, intellectual, and emotional development.

Sometime between 7 and 9 months of age, babies show vast changes. They show by their behavior that they are starting to understand concepts like "near" and "far"; they imitate more complex kinds of behavior; they show new fears—of strangers, heights, and unfamiliar objects; and on the other hand, they show a new sense of security around their parents or other caregivers. Since changes like these involve so many different psychological functions, affect processes that are so different from each other, and occur over such a short time span, some observers tie them all in with a major reorganization of brain function. This neurological development may be set in motion by one basic skill that emerges at this time—a baby's ability to crawl, which makes it possible to get around without depending on anyone else (Bertenthal & Campos, 1987; Ber-tenthal, Campos, & Barrett, 1984). (The occasional baby who skips the crawling stage but begins to walk upright very early would, presumably, go through the same kinds of changes.)

How does crawling exert such a powerful influence on babies' lives? Basically, it gives them a new view of the world. When Jason was carried, he paid little attention to his surroundings. But when he began to crawl, he became very sensitive to where objects were, how big they were in relation to each other. He started to pay attention to what objects look like—and indeed, studies have shown

that babies who are already crawling are able to tell apart similar forms that differ in color, size, and which way they are situated in space (Campos, Bertenthal, & Benson, 1980). In other research (discussed in Chapter 6), babies were more

successful in finding a toy that was hidden in a box whe-they crawled around the box than when they were carrier around it (Benson & Uzgiris, 1985).
Moving around on their own also helps babies learn t< judge distances and to perceive depth. Depth perception seems to be due less to maturation and age than to babie-experience in getting around by themselves—on all four-in infant walkers, or walking upright. Perceiving depth doe-not imply fear of high places, however. When babies fir--become aware of depth, their heartbeat slows down; it -only sometime later that the heart rate speeds up, indicating fear. When babies start to move around by themselves, the. put themselves in danger of falling, and so, to keep ther from getting hurt, their caregivers usually hover o\v them, remove them from dangerous locations, or cry 01/ and jump up when the babies are about to get into trouble. Babies are sensitive to these actions and emotions-and learn to be afraid of places from which they migb-fall.