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

Res

olut

ion

“Qua

lity”

(Q

10)

clicks

Spectral resolution development with abnormal experience

Age

Res

olut

ion

“Qua

lity”

(Q

10)

baby adult baby adult

Sanes and Constantine-Paton (1985)

Effects of experience on localization by barn owls

Reorganization of perceptionC

ue 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 motherstressed 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

Infa

nt

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

Experimental Control

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 experienceStructure 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.