As has been suggested above, the first 2 years of life is an amazing time of growth and change, both physically and mentally. Babies experiment with and learn from the environment around them. Beyond physical, thinking, and language tasks, babies are learning about social and emotional tasks. This section will discuss how babies learn not only to express their feelings and emotions, but also how they learn to understand other people's feelings. Early research led experts to believe that emotions are learned through human interaction, but newer research leads experts to believe that some emotions are naturally occurring and instinctual from birth. However, as suggested by Bronfenbrenner's theory, the environmental experiences babies have as they grow and develop are also important influences in their emotional and social development.
Babies can feel interest, distress, disgust, and happiness from birth, and can communicate these through facial expressions and body posture. Infants begin showing a spontaneous "social smile" around age 2 to 3 months, and begin to laugh spontaneously around age 4 months. In addition, between ages 2 and 6 months, infants express other feelings such as anger, sadness, surprise, and fear. Between ages 5 and 6 months, babies begin to exhibit stranger anxiety. They do not like it when other people hold or play with them, and they will show this discomfort visibly. Previously, they would smile at anyone and allow them to hold them. However, during this time babies are learning not only how to show their own feelings, but also how to notice others' feelings. Around age 4 months, infants can begin distinguishing the different emotional expressions of others. Later, around age 6 months, babies begin to mimic the emotions and expressions they see in others.
At birth, babies treat caregivers more or less interchangeably, unequipped as they are, by and large, to distinguish among people. However, as the months of their first year go by and their perceptual and processing abilities grow, they begin to form a powerful attachment or bond with their primary caregivers. As babies' attachment to their primary caregivers strengthens, they become more sensitive to the absence of their caregivers. Around age 8 to 10 months, babies start to experience separation anxiety when separated from their primary caregivers. The intensity of this anxiety varies between individuals and is based on baby's temperament and environment. While some babies will respond very strongly and heatedly to caregiver absence by crying and fussing, others will respond in a more subdued fashion through whimpers and slight agitation. It's during this period, around age 9 months, that babies first frown to show displeasure or sadness. It's also during this time that babies' temperaments, or innate personality styles, begin to show. More will be said about temperament shortly.
By nine months of age, babies have learned how to express a wide variety of emotions. This becomes readily apparent between ages 9 to 10 months, as babies become highly emotional. They go from intense happiness to intense sadness/frustration/anger quickly. This emotional lability evens out as babies develop rudimentary strategies for regulating their emotions around age 11 months.
Babies' understanding of others' emotions grows as well. Around age 12 months, babies become aware of not only other peoples' expressions but also their actual emotional states, especially distress. They're beginning to make the connection that expressions match an inside feeling. It's interesting to note some babies begin to exhibit jealousy at the end of this first year, around age 12 months.
As toddlers move into the end of the second year, they continue to build on the emotional progress they have already made. Between the ages of 13 and 18 months, separation anxiety may subside as object permanence develops, and they understand their caretaker isn't gone even when they can't see them. This is also the point during which babies may also use transitional objects such as stuffed animals or blankets to soothe and comfort themselves when the caretaker is not there. Toddlers usually enter another emotionally rocky time between the ages of 15 to 18 months. During this time, they can be fretful and easily frustrated, and may throw temper tantrums to demonstrate this emotionality. Toddlers often come out of those "Terrible Twos" around age 21 months, and become less fretful and more relaxed. Also during this time, toddlers may show signs of self-consciousness when doing certain tasks or trying new situations, looking for caretaker approval.
By age 2, toddlers can show a wide range of emotions and are becoming better at regulating and coping with their emotions. In fact, by this age, toddlers can even fake some emotions in order to get what they want. They know that if they fall and show behaviors of being hurt (even if they aren't hurt), they will get attention. However, they will often still become upset at situations that disrupt their sense of control or alter their normal routine. Also around their second birthday, genuine empathy appears. They become capable of recognizing when they've hurt someone somehow, and capable of apologizing.