HDP 1 Midterm ReviewFall 2005

Topics coveredWEEK 0

Th 9/22 Introduction to course (Jeff Elman, Dept. of Cognitive Science)

WEEK 1Tu, 9/27 Infancy and Evolution (Jim Moore, Dept. of Anthropology)

Th 9/29 The History of Childhood (Stefan Tanaka, Dept. of History)

WEEK 2Tu 10/4 Genes, Brain Development and Behavior (Leslie Carver, Dept. of Psychology)

Th 10/6 Brain Development: The Basics (Joan Stiles, Dept. of Cognitive Science)

WEEK 3Tu 10/11 CLASS CANCELLED

Th 10/13 Development of Visual Perception (Karen Dobkins, Dept. of Psychology)

WEEK 4Tu 10/18 Conceptual Development (Gedeon Deak, Dept. of Cognitive Science)

Th 10/20 Social Development (Gail Heyman, Dept. of Psychology)

WEEK 5Tu 10/25 Autism (Aubyn Stahmer, Children’s Hospital)

Introduction (Elman)

Important terms and concepts

• Maturation

• Learning

• Adaptation

• Evolution

• Emergentism

• Genetic conservatism

• The “Gene for X” fallacy

• Nature vs. (or and?) Nurture

The “Gene for X” fallacy

More DNALess DNA

Genetic conservatism

The power of the environment

from butterfly host from alderfly host

Trichogramma (wasp)

from butterfly host from alderfly host

Trichogramma (wasp)

Emergentism

• The whole is greater than the sum of its parts

• Interactions create complexity

• Outcomes are not easily predictable

• Multiple sources of causation

• A prime example: Language

Infancy & evolution (Moore)

Important terms and concepts

• Life History Theory

• 5 stages of development

• The “obstetric dilemma”

• Bipedalism

• precocial species vs. altricial species

very rapid growth, but rate

falling fast

slower, even

growth

sudden rapid

growth again, then rapid fall in

rate

growth stops

growth rate drops

INFANT(ends at weaning – 36 mos)

CHILD(ends at end of brain

growth – 7 yrs)

JUVENILE(ends at end of

dependence/puberty – 10-12 yrs)

ADOLESCENT(ends when socially & physically

adult-like – 19-25 yrs)

ADULT

LIFE HISTORY THEORY

“…natural selection favors organismic life

cycles in which resources are allocated

among growth, maintenance and reproduction

in relation to age or size in a manner that

maximizes the reproductive potential across

individual life spans.” Pereira 1993

A big question

• Why do humans extend the immature period?

Breaking it down…

• What is the reproductive disadvantage of extended immaturity?

• What might compensate for this disadvantage?

• What does the “obstetric dilemma” refer to?

The obstetric dilemma

1. Bipedalism associated with change in pelvic structure & smaller birth canal

2. Evolution of humans associated with increased brain size

3. Energy cost for mother to continue supporting fetal brain development

A possible solution

Be born “early”, and have an extended transition from infancy to adulthood

Also: create “childhood”

a. Reduced nutritional needs

b. Help with caring for younger siblings

c. Gets young brains into enriched environment

The history of childhood (Tanaka)

Important terms and concepts

• Functional imperfection

• Ages of man

• John Locke (ideas about childhood)

• Emile Rousseau (ideas about childhood)

• Industrial Revolution (impact on childhood)

• Tutelary complex

• History of public education

History of childhood

• Culturally, childhood is modern and somewhat peculiar to the U.S.

• Early views on childhood: “little adults”

• Later:– J. Locke: “tabula rasa”

– E. Rousseau: to be protected and nurtured

• Industrial Revolution’s effects on child labor

– Factories were dangerous environments

– Produced asymmetric growth & deformities

– Separated children from families

• Tutelary complex as response to

– Industrial Revolution

– Immigration and Migration

• Public education

– When? Mid-1800s

– Why? Socialize the poor & working class

Genes, brain development, & behavior (Carver)

Important terms and concepts

• Behavior Genetics (what is it? how does it work?)• Variation• Hereditability (as defined by Behavior Genetics)• Methods (twin studies; adoption studies)• Shortcomings and problems with B.G.• Reproductive cycle (meiosis, mitosis)• “Cross-over” events• (Do not need to know 6 phases of meiosis)• Embryogensis (what happens when, and where)• Early neural events: (see also Stiles lecture)

– proliferation– Migration– differentiation

Behavior Genetics• Goal:

– Measure how different people are, as a function of how closely they’re related

• Definition of heritability– what is odd about this definition?

• Shortcomings– Of twin studies– Of adoption studies

Basics of genetics

• 22 pairs of chromosomes, plus 1 pair of sex chromomes (X-X, X-Y)

• Meiosis (reproduction):– 1 cell produces 1 cell– Introduces variation

• Mitosis (basic cell division):– 1 cell produces 2 cells

Brain development – the basics (Stiles)

Important terms and concepts

• Basic questions:– How does such a complex organ as the brain get built?

– How plastic/adaptable is the brain, in response either to damage or to abnormal experience?

• Important terms:– ectoderm, endoderm, mesoderm

– neural tube

– proliferative zones

– glial cells, neurons, radial glial cells

– cell birthday

– Radial Unit Hypothesis; protomap vs. protocortex hypotheses

– active transport vs. passive transport; “inside-out” organization of the cortex

– cortex (i.e., “cortical mantle”)

– laminar organization of cortex

– white matter; gray matter

– “productive events”; “subtractive events”; synaptogenesis

The human brain

FrontalLobe

ParietalLobe

OccipitalLobe

TemporalLobe

Corpus callosum

CORTEX(neurons;

“gray matter”)“white matter”

(axons)

Brain facts1. Brain weight (adult and newborn)

3 lbs (adult); 0.8 lbs (newborn)

2. Number of neurons in cortex: 20 billion

3. Number of synapses:60 trillion

4. Rate of early neuron growth & when greatest?1st half of pregnancy200,000/minute

7 important stages

1. Development of neural plate E12

2. Formation of trilaminar disk begins E15

3. Formation of neural tube begins E18

4. Neural tube closes (top; then bottom) E25; E27

5. Ventricular zone progenitor cells start dividing (symmetrically) E28

6. VZ asymmetric cell growth (neurogenesis) starts E42

7. Greatest production of neurons E42-E125

AnencephalySpina bifida

What parts of the neural tube become what parts of the brain?

Ventricules: (fluid-filled) holes in the middle of the brain

Ventricular zone: inner surface of hollow tube where progenitor cells lie

Then…

• Migration – Cell’s birthday– Role of radial glial cells– “inside/out” pattern of migration– 6 cortical layers

• Cell differentiation

• Subtractive events

Importance of experience & cell activity

(eyes)

(ears)

(auditory cortex)

(visual cortex)

Importance of experience & cell activity(“re-wiring the ferret” experiment)

(eyes)

(ears)

(auditory cortex)

(visual cortex)Now acts likevisual cortex!

Development of visual perception (Dobkins)

Important terms and concepts

• Basic questions:– What are the perceptual consequences of neural changes?– How is infant vision different from adult vision?– What are the clinical implications?

• Important terms:– sensitivity– threshold/contrast threshold– contrast– spatial frequency– grating stimulus– psychophysics– Snellen exam– acuity

Important terms and concepts

• Important terms (cont’d.):– focus– luminance– chromatic– depth perception– stereopsis– binocular vision– monocular vision– photoreceptors (differences between infant and adult,

shape and spacing)

Methods

Q: how do you test adults’ vision?

Q: how do you test infants’ vision?

Q: what level of performance is considered the threshold?

Q: what is the difference between threshold and sensitivity?

Sensitivity

- measures sensitivity to contrast

Acuity

- measures to fine detail

- spatial frequency

1 degree

3 cycles/deg

1 degree

6 cycles/deg

The “rule of thumb”:

1 degree ~= what your thumb covers at arm’s length

0.150

60

70

80

90

100

1 10Luminance Contrast (%)

Adult Data

Threshold = 0.7%

Sensitivity = 1/thr * 100 = 143

Lower threshold is betterHigher sensitivity is better

Changes in infant photoreceptors

Hendrickson & Yuodelis, 1984

Adult

Newborn22 weeksgestation

What determines sensitivity?morphology

What determines acuity?spacing

Changes in infant vision…

• Acuity and Sensitivity– adult like by 3-5 years

• Color – compared with adults?

Infants possess equally low sensitivity for BOTH Luminance (Black/White) andChromatic (Red/Green) stimuli

INFANT COLOR VISIONIS RELATIVELY FINE!!

Luminance

Chromatic

age(months)2 3 4 5

10

1000

100

4

Low SFC

on

tras

t se

nsi

tivi

ty

Age (in months)

Ad

ults

Luminance

Chromatic

Changes in infant vision…

• Acuity and Sensitivity– adult like by 3-5 years

• Color – compared with adults?

• Optimal visual stimuli for an infant?

Conceptual development (Deak)

Important terms and concepts

Important terms:– “what” and “where” pathways

• Which is ventral stream? Which is dorsal stream?

– Object permanence– Means-end grasping– A-not-B error– False belief error– Attention-sharing (gaze- and point-following)

Timelines

• Object permanence– At 4 mos: only motion matters– By 6-7 mos: shape, color, texture, etc. matter

• Means-end grasping– By 5 mos, can grasp– By 6-7 mos, show means-end grasping– By 8 mos, show “choosy [smart] reaching”

• A-not-B error– 8-9 mos will perseverate

A B C

How do you interpret “surprise”(longer looking time)?

Which of the 2nd two displays would cause surprise at what ages? Why?

Timelines (cont’d.)

• Object awareness– 6 mos: learn features that “go together”– 10 mos: correlate object features w/location

• Use of gaze- and point-following– 6 mos: follow if objects are in view (front of infant)– 9 mos: follow if objects are in peripheral view– 12 mos: follow if objects are out of sight (back of infant)

Social development (Heyman)

Methodological challenges

• Correlation vs. causation

• Multiple sources of causation

• Constraints on naturalistic (vs. experimental) data

Milestones

• Newborns: imitation; preferences for mother’s voice

• 12 mos: stranger & separation anxiety

1st attempts at comforting & hurting

social referencing

• 18 mos: aware that others’ desires may differ

• 2 yrs: “terrible 2s”: independence

private speech

transition from parallel play to joint play

Milestones

• 3 yrs: same-sex preference

ability to hide emotions

• 4 years: able to pass “false belief” test

• 5 years: gender constancy

understand difference between real

and apparent emotion

• 6yrs: understand more complex emotions

(pride, shame, etc.)

Autism (Stahmer)

Important terms and concepts

• Definition of Autism Spectrum Disorder

• Echolalia

• Playlalia

• Incidence of autism

• Gender differences

• Etiology (=likely cause)

• Discrete Trial Training

• Pivotal Response Training (& profile of best responders)

Diagnosing Autism Spectrum Disorder

• What 3 things are needed?

– Deficits in social behavior & attachments

– Deficits in verbal & nonverbal communication

– Perseverative, stereotyped, repetitive behaviors

Behavioral treatments

• Discrete Trial Treatment

– Presenting instructions and questions:• Child attending• Easily discriminable instructions• Short and consistent instructions

– Child responds or fails to respond

– Consequences• Clear, consistent consequence (positive)

Limitations of DTT?

• Failure to generalize to novel situations

• Lack of spontaneity

• Robotic-like behavior

• Require familiar prompts to engage behavior

• Slow and time-consuming

• Not easy or pleasant for child or trainer

Pivotal Response Training

• Emphasizes– Child choice (behaviors child wants to do)– Direct reinforcement– Intersperse maintenance (easy) tasks– Frequent task variation– Turn taking: let child initiate– Tasks involve multiple simultaneous cues

Assessment

• Which child characteristics best predict success on Pivotal Reponse Training?

– High toy use

– Low avoidance behaviors

Exam information

• Be on time: the exam will take 70-75 minutes

• Bring only pens/pencils

• Eyes and papers on desk!

• Know and write on each page:– Your name

– Your PID (e.g., A01234567)

– Your Section ID (A02, A08, A11, etc.)

– Your TA’s name and the day and time of your section

• Coverage: – Lecture = 70%; readings = 30%

• Format:– 73 questions (most worth 3 pts)

• 42 multiple choice

– Beware of “Which of the following is NOT…” questions

– Only 1 answer will be correct for M.C. questions

• 9 True/False

• 22 fill-in-the-blank, matching, short answer

• Grading

1) The evolutionary tension between infant brain size and female pelvic shape in humans is typically referred to as the: [3 pts]

a) obstetric dilemma

b) gynecological situation

c) neural expansion hypothesis

d) big brain problem

2) Explain, in 3-4 sentences, what is meant by the “gene for X” fallacy? [3 pts]

3) True or False: White matter refers to the outer layer of cells on the brain, also known as the cortex. [3 pts]

a) T

b) F

4) Which of the following is NOT true of young children? [ 3pts]

1) Most children pass the “false belief” test by 4 years of age.

2) Most children become aware of gender constancy by 3 years.

3) Few children below the age of 4 years understand the concept of gender constancy.

4) Children become aware of more complex emotions around 6 years.

Good luck!