Infants exposed to two languages (e.g., Japanese and English) in the first seven to eight months of life will easily develop the neuron functions that can differentiate the sounds of the two languages. This sets a base for fluent mastery of both languages without an accent later in development. Individuals who develop capability for two languages early in life have a larger left temporal hemisphere of the brain than do individuals with monolingual backgrounds. This may be, in part, an explanation of why those individuals can also more easily master other languages later in life. (Mustard, J. Fraser, MD. Early Childhood Development: How does experience in early life affect brain development? 2008. p. 12.)

Unimpaired human beings are born with the brain capacity for learning any language in the world. (Restak, Richard, MD. The New Brain. PA: Rodale, 2003, pp 10-11)

At birth the brain is capable of distinguishing the sound units, or phonemes, of all human languages. During the first six months of life of exposure to language, the tunes itself to recognize the phonemes that are present in its native language, discarding those that aren’t. (Quartz, Steven R., PhD, and Terrence J. Sejnowski PhD. Liars, Lovers, and Heroes. NY: HarperCollins Publishers Inc., 2002, p 42)

The language areas become active about eighteen months after birth. The one that confers understanding (Wernicke’s area) matures before the one that produces speech (Broca’s area), so there is a short time when toddlers understand more than they can say—a frustrating condition that probably does much to fuel the tantrums that typify the “terrible twos.” (Carter, Rita, Ed. Mapping the Mind. CA: University of California Press, 1998, p 20)

During first few weeks of life a babbling baby utters almost every sound of every known language. Later, as child master a single language, the ability to make some sounds vanish. This is an example of pruning. (Brynie, Faith Hickman. 101 Questions Your Brain Has Asked About Itself But Couldn’t Answer, Until Now. CT: Millbrook Press, 1998, p 21)

Babies who learn two languages at the same time have a single brain region for both languages. (Greenwood-Robinson, Maggie, PhD. 20/20 Thinking. NY: Avery, Putnam Special Markets, 2003, p 249)

By 12 months infants have discovered the sounds (phonemes) used to convey meaning in their native language. After this time they lose the ability to distinguish non-native speech contrasts. Language understanding becomes lateralized to the left hemisphere by the age of two. (Greenfield, Susan, Con. Ed. Brain Power. Great Britain: Element books Limited, 1999, pp 53, 163)

The male brain is wired differently from female brain. Language is a more difficult skill for boys to acquire and use effectively in learning than it is for girls. (Gurian, Michael, PhD, and Patricia Henley, with Terry Trueman. Boys and Girls Learn Differently! CA: Jossey-Bass, 2001, p 110)

About the same time as the language areas become active, myelinization begins in the prefrontal lobes. The reticular formation (e.g., maintaining attention), usually only becomes fully myelinated at or after puberty, which is why prepubescent children have a short attention span. The frontal lobes do not become fully myelinated until full adulthood (e.g., younger adults are more emotional and impulsive than older individuals). (Carter, Rita, Ed. Mapping the Mind. CA: University of California Press, 1998, p 20)