INTRODUCTION world, our brain becomes a thicket of neural connections. There are an estimated quadrillion (1,000 trillion) Babies were once viewed, in the words of English neural connections in the adult brain. To measure the philosopher John Locke, as blank tablets. Research in effects of the environment on the developing brain, early neuroscience over the past few decades has proven him studies examined rats raised either in an enriched enviwrong. Babies are like computers. Of course, there are ronment (with wheels to spin, ladders to climb, and major differences. Instead of microchips, the brain conother rats to play with), a deprived environment, or sists of neurons. However, like computers, babies take alone (Diamond, Krech, & Rosenzweig, 1964). Results in and process information from the world right from of the study showed that rats having the enriched envithe start. ronment had significantly more neural connections than The purpose of this article is to examine current those raised in the deprived environment or alone. Rats research on babies’ brain development. In particular, with thicker brains were smarter, figuring out how to run what does research tell us about babies’ ability to undermazes and find food faster. The enriched environment stand basic numerical concepts and arithmetic operaprobably matched the real world for rats living in the tions? wild. The results do not imply that extra stimulation produces a thicker rat brain but that a normal environment leads to better outcomes than a deprived environment. HARDWIRING THE BRAIN The same may also be true for human babies. Parents do not have to provide extra stimulating experiences Scientists have focused their attention on two aspects of the brain. One is neurologically based, shaped above and beyond what they would ordinarily do with their babies, such as responding to their cues and talking by evolution. The other is culturally based, shaped by learning. However, this dichotomy is misleading (Gopto and touching them (Ramey & Ramey, 1999). At birth, a baby’s brain is only one fourth the size nik, Meltzoff, & Kuhl, 1999). The evolution of the brain has influenced the kinds of learning strategies and culthat of the adult. What is added is not more neurons but an intricate network of connections between them. tural adaptations humans have acquired over time. In fact, the protracted period of immaturity during infancy Individual neurons communicate with each other in particular ways as when the retinas of send a visual image and childhood allow children to learn about their specific social environment (Bjorklund, 1997). of a human face to the brain. Even before birth, connections between neurons result from the spontaneous Babies’ brains change as a result of their give-andtake interactions with the world. Neurons are designed bursts of electricity or firing. Groups of neurons have been found to send signals in waves in trying to signal to respond to information from the outside world in specific ways, sending it on to other parts of the brain. other cells. Connections are formed with cells firing together. A favorite saying of neuroscientists is, “Cells However, the brain is also a dynamic system. Its parts are constantly in dialogue with each other. There are that fire together wire together.” After birth, sensory input floods the neurons, spurring a flurry of new connecover 100 billion neurons in the brain, about the same number of stars in the Milky Way. Hundreds of thoutions. As they signal to one another, permanent connections are formed. Over time, individual neurons form sands of neurons are involved in processing every bit of information the brain receives, although we only permultiple branches with each other. Some branches, called axons, send out information while others, called ceive a fraction of it at the conscious level. We participate in building our own brains from dendrites, receive information. The space between one cell’s axon and another’s dendrite is referred to as a synbirth. Based on our unique encounters with the real