200)Psycholinguists have found that children not exposed to adult language may invent a language of their own. 201)Infants are not able to derive simple linguistic rules from a string of sounds until they are about 18 months old. 202)Infants as young as six weeks can derive simple linguistic rules from a string of sounds. 203)Infants as young as seven months can derive simple linguistic rules from a string of sounds. 204)Many psycholinguists believe that an innate capacity for language evolved in humans because it enhanced chances for survival. 205)Scientists have identified at least two genes that are responsible for language. 206)Those who believe that language and grammar are innate deny that nurture plays any significant role in language development. 207)Heritability is defined as a statistical estimate of the proportion of the total variance in some trait that is attributable to genetic differences among individuals within a group. 208)Heritability estimates apply to specific individuals, to differences between groups, and to differences within groups. 209)Because IQ is highly heritable, school achievement and IQ cannot be boosted much.