Control over one's motor behavior ranks among the infant's greatest achievements.Psychologists who study the acquisition of motor skills in children find it useful to distinguish between gross motor development, that is, motor skills which help children to get around in their environment such as crawling and walking, and fine motor development, which refers to smaller movement sequences like reaching and grasping.

The development of motor skills has implications beyond simply learning how to perform new actions: motor skills can have profound effects on other areas of development. For example, researchers have shown that infants with locomotor experience (experience moving around their environment) were less likely to make errors while searching for hidden objects. The ability to initiate movement around one's environment stimulates the development of memory,making hidden object tasks easier to solve. Psychology professor Carolyn Rovee-Collier argues that the onset of independent locomotion at around nine months old marks an important transition in memory development. Children who can move about the environment develop an understanding of locations such as here and there. Because infant memory is initially highly dependent on context that is, the similarity between the situation where information is encoded (stored in memory) and where it is recalled, infants who have experience moving about the environment and who learn to spatially encode information become less dependent on context for successful recall.These examples show that gross motor development has implications beyond the immediately apparent benefits of crawling and walking.

Renowned psychologist Jean Piaget argued that the development of reaching and grasping was a key aspect of development because it formed an important link between biological adaptation and intellectual adaptation. Reaching and grasping are voluntary actions under the infant's control, and as such, they open up exciting new possibilities in their ability to explore the environment. An infant who reaches for and grasps an object so as to explore it pushes his development forward as he engages in processes such as adapting his grip to the size and shape of the object. Piaget argued that these early processes drive cognitive development in the first two years of an infant's life.

The development of reaching begins early on in life. Newborn infants seated in an upright position will swipe and reach towards an object placed in front of them, a behavior labeled "prereaching." These poorly coordinated behaviors start to decline around two months of age and are replaced by "directed reaching" which begins at about three months of age. At this time reaching becomes more coordinated and efficient, and improves in accuracy. According to research conducted by Clifton et al., the infant's reaching does not depend simply on the guidance of the hand and arm by the visual system but is controlled by proprioception, the sensation of movement and location based on the stimulation arising from bodily sources such as muscle contractions. By about nine months old, infants can adjust their reaching to take into account a moving object. However, nine month olds are far from expert reachers. A good deal of skill must still develop.

Once infants begin reaching they also begin to grasp the objects that are the target of their reaches. The ulnar grasp is seen when infants first engage in directed reaching. The ulnar grasp is a primitive form of grasping in which the infant's fingers close against its palm. The fingers seem to act as a whole, requiring the use of the palm in order to hold an object. Shortly after this accomplishment, when infants can sit upright on their own, they can acquire the ability to transfer objects from hand to hand. Around the end of the first year, infants will have graduated to using the pincer grasp where they use their index finger and thumb in an opposable manner (placing them opposite each other), resulting in a more coordinated and finely tuned grip which allows for the exploration of very small objects or those objects which demand specific actions for their operation,such as the knobs on a stereo system which require turning to the left or right to adjust volume.

能够个人的运动行为对于儿童而言，是最重要的成就之一。研究儿童运动技能习得的心理学家发现，这对于区分运动发育的是否良好很有用，也就是说,帮助孩子在周围环境中学会活动的运动技能，如爬行和走路和精细化动作发展，这是指较小的运动序列，如达到和把握。 运动技能的发展不仅仅是简单地学习如何进行新的动作，它还能对其他领域产生深远的影响。例如，研究人员已经表明，有运动经验的婴儿（在周围环境中移动的经验）在寻找隐藏物体时不太可能犯错误。在某个环境中发起运动的能力刺激了开发，使隐藏的对象任务更容易解决。心理学教授卡罗琳洛维-科利尔认为，孩子大约9个月大的运动的开始标志着记忆发展的一个重要转变。可以在一个地方移动的孩子对这里和那里的位置有一个了解。因为婴儿的记忆最初高度依赖于情境，即信息编码（存储在记忆中）和记忆的情况之间的相似性，这些婴儿在一个地方移动并且不那么依赖学习空间编码信息的能力，这些例子表明，精细化动作发展的比爬行和行走有更显而易见的好处。 著名的心理学家皮亚杰认为，伸出和抓住是发展的关键，因为它在生物适应与智力适应之间有重要联系。伸出和抓住是婴儿控制下的自愿行为，因此，他们开拓探索环境能力上有新的可能性。一个婴儿伸手抓住一个物体，以便很好探索物体，当他根据物体的大小和形状调整他自己手掌的过程时，这也推动了他的发展。皮亚杰认为，这些早期的过程会在婴儿生命的头两年驱动认知发展。 孩子在生活的早期就在学伸手。新生婴儿会直立坐着并把手伸向面前的一个物体，这种行为标记为“伸手之前”。这些协调不佳的行为在两个月左右开始衰退，并由在大约三个月大时所开始的“直接伸手”取而代之。此时婴儿伸手将更加协调和高效，并提高了准确性。根据克利夫顿等人的研究，婴儿的接触不仅仅取决于视觉系统对手和手臂的引导，而是由本体感受控制，运动和位置的感觉基于肌肉收缩引起的刺激。大约九个月大的时候，婴儿可以调整伸手距离，来触摸移动的物体。但是，九个月大的孩子还是不能很熟练的拿东西。很多技能仍然必须发展。 一旦婴儿开始接触东西，他们也就要开始抓住他们目标的物体。当婴儿第一次接触到的东西时候，尺骨就会感受到。尺桡骨抓握是一种原始的抓握形式，当婴儿的手指靠近手掌时，手指看起来像是一个整体，需要使用手掌才能握住物体。在完成这项工作后不久，婴儿可以自己坐直时，他们就可以获得将物体从手上移到另一个手上的能力。大约在第一年结束时，婴儿将逐渐会使用夹钳抓住东西，他们用食指和拇指以可对立的方式（将他们放置在彼此对面），能够更协调和精细的控制，从而可以摸索非常小的物体或需要特定动作来进行操作的物体，如音响系统上的旋钮需要转向向左或向右调整音量。