I promised you more about what's going on in the 4-month old baby's emotional world. With this post, I'm going to try to give you a flavour for how big a difference one month makes at this early stage in development. Many developmentalists see the 3–4 month period as the fruition of a “love affair” between the infant and the caregiver. But it is a love affair with all the qualities of a still life. It doesn’t progress from moment to moment, and that’s because babies that age can't keep track of what to expect, what happens next. The cognitive software simply isn’t there yet—not until babies reach 4 months. That’s why, before about 4 months, regardless of how intensely your baby gazes at you, no matter how giddily she cooes and giggles at the glorious sight of your smile, there is no disappointment when the interaction ends—as long as it is followed right away by something else the baby can attend to. Even when left alone on a play mat, when you've gone off to pee, to answer the phone, to get a drink, 2 – 4-month old infants will generally not fuss if they are distracted by something interesting, at least not for a few minutes. That's why distraction is such an effective means of dealing with a 3-month old's crying. Oh no! Mama's gone! Waaaaaaaa! Hey… look at that fuzzy coloured ball… rattle, rattle, bounce, rattle… mama who?

It is at around 4 months that mother-infant reciprocity — that intense emotional dance of gazes and coos — peeks and it's a key transition point described by Margaret Mahler, an infant observer with a background in psychoanalysis. Mahler says that at 4 months begins a phase of “differentiation” of the infant from the mother marked by a mushrooming sense of autonomy. It may seem counter-intuitive that a period of increasing closeness should lead to a spurt in autonomy. But it's no accident. The love, excitement, and learning that flow between infant and caregiver during their face-to-face exchanges at around 3-4 months push the infant into a major developmental advance, a sort of blossoming of awareness that results in a sense of a self—an I—who can act on the world out there. Yet autonomy does not mean that the bond with the parent is over. Quite the contrary. Mahler emphasizes that the baby’s sense of a unique, separate self forms the basis of a new kind of bond with the mother—a bond between two partners, rather than a fusion in which mother and baby act as parts of a single organism. Infants now begin to interact with their caregivers in a back-and-forth fashion (as I described in detail in Part I). Also at this age, infants begin to initiate play and wait for the parent to respond to them. So the onset of differentiation at 4 months is a time of both budding autonomy and increased interpersonal engagement, leading to true play for the first time ever. The time babies spend gazing at mother’s face now begins to decline, but their attraction to game-playing skyrockets. Almost any kind of game will do, as long as it involves some repetitive, expectable activity. By 5 months, infants love the feeling of excited anticipation they get while waiting for the parent to swoop down, pat or tickle them, or throw them up in the air. When they feel lonely, or bored, or tired, they are now obsessed with their new-found power to initiate their parents' engagement and they now EXPECT parents to be on call for the next game to begin.

So the plot thickens for the 4-month old. And it's not hard to see why this developmental transition is such a difficult one for so many of us parents who are trying to take a break from the fun and games for one or two blessed hours, at least between 2 and 4 am…