Models of Development How do the initial characteristics of the individual and of the environment result in the behavior we see?

Typical v. individual development

Effects of experience on development of sound encoding Spectral resolution development with normal experience Age Resolution “Quality” (Q 10 ) clicks Spectral resolution development with abnormal experience Age Resolution “Quality” (Q 10 ) baby adult Sanes and Constantine-Paton (1985)

Effects of experience on localization by barn owls

Reorganization of perception Cue 1 Cue 2 Cue 1 Cue 2 Cue 1 Cue 2 Cue 1 Cue 2

Development of cortical EP in children with CI

Cellular mechanisms of cortical development: Long-term potentiation LTP is involved in neural plasticity. LTP is eliminated when cochlear input is eliminated. Electrical stimulation of cochlea maintains LTP.

People differ, even in perception How do individual differences arise during development?

Models of development Genes Genes set limits Gene-environment interaction Gene-environment transaction

Genes determine behavior

Genes set the limits

Genes set the landscape

Gene-environment transactions

How can experience change genes?

Genes make proteins

DNA Methylation Differentiation Chromosome inactivation Transcriptional silencing Can be triggered by experience Can be heritable

Example: Maternal behavior and stress response

“Acquired trait” is heritable

Mechanism, Initial biases, Critical period Bad mother demethylates DNA Genes start out methylated: Bias to be outgoing and good mother The effect only occurs between P1 and P6 days Stressed mother  stressed babies – adaptive significance

GENES AND ENVIRONMENT CHANGE EACH OTHER conclusion

Mother nature counts on experience to guide development

Imprinting: Genetic program for behavior?

Species-specific call recognition?

Gottlieb: Embryonic experience crucial to postnatal social behavior

Apparatus for testing postnatal social behavior

Gottlieb: Embryonic experience crucial to postnatal social behavior Devocalized duckling approaches chicken call as often as maternal duck call Exposing embryo to embryonic duck call reinstates preference for maternal duck call Exposure to chicken call leads to preference for chicken call* *only in ducklings who had tactile contact with other ducklings

Effects of prenatal experience What looks “innate” may result from experience Dependence on experience as economical approach Susceptibility to experience allows for adaptation to environmental conditions

Could prenatal sound exposure be important for human development?

Newborns prefer speech to sine- wave speech

Effect of prenatal exposure to maternal voice

Newborns recognize mom’s voice ∆ Interburst interval Infant

Newborns’ voice recognition Can discriminate male voices, but don’t prefer dad Prefer low-pass filtered version of mom’s voice over full-spectrum version at birth

Do newborns prefer familiar speech? OR Why we can have lots of good fun if you wish, with a game that I call UP UP UP with the fish! ?

Newborns prefer familiar speech ExperimentalControl

Native language perception by newborns Newborn infants prefer native speech over nonnative Newborns discriminate native v. nonnative across prosodic categories Five-month-olds discriminate native v. nonnative within prosodic category Newborns?

Effects of prenatal exposure to speech Newborn infants respond differentially to maternal voice Newborn infants have learned something about the properties of their native speech Long-term effects?

Postnatal experience Structure facilitates learning

VOT exaggeration

Expanded vowel triangle

Speech learning and social interaction

Speech learning depends on social interaction

Conclusions “Transactions” among genotype, epigenotype and experience drive development. Individual differences in any of these factors lead to differences in phenotype. Many of the principles identified in epigenetic studies of nonhumans seem to apply to humans.