PSY 369: Psycholinguistics Language Acquisition: Critical period?

Critical (sensitive) periods Certain behavior is developed more quickly within a critical period than outside of it. This period is biologically determined. Examples: Imprinting in ducks (Lorenz, ; Hess, 1973) Ducklings will follow the first moving thing they see Only happens if they see something moving within the first few hours (after 32 hours it won’t happen) of hatching Binocular cells in humans Cells in visual system that respond only to input from both eyes. If these cells don’t get input from both eyes within first year of life, they don’t develop

Critical (sensitive) periods Some environmental input is necessary for normal development, but biology determines when the organism is responsive to that input. That “when” is the critical period Certain behavior is developed more quickly within a critical period than outside of it. This period is biologically determined.

Critical period for language It assumes that language acquisition must occur before the end of the critical period estimates range from 5 years up to onset of puberty Lenneberg (1967) proposed that there is a critical period for human language

Evidence for critical period for language Feral Children Children raised in the wild or with reduced exposure to human language What is the effect of this lack of exposure on language acquisition? Two classic cases Victor, the Wild Boy of Aveyron Genie

Victor, The Wild Boy of Aveyron Found in 1800 near the outskirts of Aveyron, France Estimated to be about 7-years-old Considered by some to be the first documented case of autism Neither spoke or responded to speech Taken to and studied by Dr. Jean-Marc-Gaspard Itard, and educator of deaf-mute and retarded children Never learned to speak and his receptive language ability was limited to a few simple commands. Described by Itard as “an almost normal boy who could not speak”

Genie Found in Arcadia, California in 1970, was not exposed to human language until age Raised in isolation a situation of extreme abuse Genie could barely walk and could not talk when found Dr. Susan Curtiss made great efforts to teach her language, and she did learn how to talk, but her grammar never fully developed. Only capable of producing telegraphic utterances (e.g. Mike paint or Applesauce buy store) Used few closed-class morphemes and function words Speech sounded like that of a 2-year-old

Genie By age of 17 (after 4 years of extensive training) Vocabulary of a 5 year old Poor syntax (telegraphic speech mostly) Examples Mama wash hair in sink At school scratch face I want Curtiss play piano Like go ride yellow school bus Father take piece wood. Hit. Cry.

What Do These Cases Tell Us? Suggestive of the position that there is a critical period for first language learning If child is not exposed to language during early childhood (prior to the age of 6 or 7), then the ability to learn syntax will be impaired while other abilities are less strongly affected Not uncontroversial: Victor and Genie and children like them were deprived in many ways other than not being exposed to language Genie stopped talking after age 30 and was institutionalized shortly afterward (Rymer, 1993)

Effects of the Critical Period Learning a language; Under c. 7 years: perfect command of the language possible Ages c. 8- c.15: Perfect command less possible progressively Age 15-: Imperfect command possible In some special cases, we are given a window on the nature of the critical period

Effects of the Critical Period Learning a new language What if we already know one language, but want to learn another?

Effects of the Critical Period Johnson and Newport (1989) Native Chinese/Korean speakers moving to US Task: Listen to sentences and judge whether grammatically correct