Development:
Definition & methods of study
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Overview
Defining development
 Studying development

–
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Study design
–
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Longitudinal & cross-sectional designs
Experimental, observational, and qualitative
studies
Predicted variables
–
typically behavior and/or physiologic activity
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Development defined
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Individual change that is, normative, nonreversible, relatively stable, and sequential.
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Development defined defined
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Normative process
–
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non-reversible
–
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reorganization of the entire person
relatively stable
–
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everyone’s doing it
you can’t go back,
sequential change
–
crawl before you walk
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Examples
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Is development
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Increasing functionality in all things?
–
–

Loss of perceptual acuity in non-native
languages
Old-age
Headed toward a goal?
–
–
–
Development has normative outcomes,
but time goes forward
prior events cause subsequent events
 not
the opposite
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Canalization (Waddington)
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Overview

Studying development
–
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Studying behavior
–
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Experimental and observational
Studying outcomes
–
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Longitudinal and cross-sectional
Behavior and physiology
Relate to your article reviews and final
projects
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Longitudinal
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
Same infants over
time
Pro: Answers ‘How do
individuals change in
time?’
Con: Takes a long time
–

Attrition
Final project
examples?
120
110
B a y le y C o g n itiv e S c o re

Typical Trajectory:
C ognitive Scores D ecline
100
90
80
70
60
50
1
Y ear
M = 93.5
n = 200
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2
Y ears
M = 79.1
n = 190
3
Y ears
M = 82.1
n = 132
Cross-sectional


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Different infants at
different times
Pro: Efficient, large
numbers of subjects
Con: Differences do
not necessarily reflect
individual’s
development
–

e.g. cohort
Final project
examples?
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95
90
85
80
75
70
65
60
55
50
One
Year
Two
Year
Three
Year
Different
Individuals
Longitudinal vs. cross-sectional

Development is relatively
stable on large time scales
–

But choppy on smaller scales
–

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Motor, physical, emotional,
communicative
Only longitudinal research can
show this
Emergent order from chaotic,
dynamic systems
Previous example?
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Hypothetical applied example
from Lamb et al.
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Individual differences
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Complementary, not exclusive

A single study can combine longitudinal
and cross-sectional methods
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Some infant studies use neither method
–
They look at behavior at one point in time
 E.g.,
Neonate study
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Predictor and predicted variables
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In developmental studies,
–
–

age is a predictor
behavior or physiology are predicted
Experimental and observational studies
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Stability and continuity
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Stability
–
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Rank of individual in group is stable
Continuity
–
Level of behavior is continuous across ages
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Experiments are unique because
They can demonstrate causality
 How?
E stim a te d M a rg i n a l Me a n s

Estimated Marginal Means of MEASURE_1
.16
.14
.12
.10
.08
.06
EXP2
.04
Comparison
.02
Exposed
1
SMILES
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2
3
Experimental design
Between subject
–
–

A treatment (independent variable) is
assigned randomly
creating treatment and control groups
Within-subject
–
–
All infants get treatment and control
Examples
 Rating
E stim a te d M a rg i n a l Me a n s

study, Face-to-face still-face
Estimated Marginal Means of MEASURE_1
.16
.14
.12
.10
.08
.06
EXP2
.04
Comparison
.02
Exposed
1
SMILES
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2
3
Constrained behavior in
experiments

Gazes at stimulus
–
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habituation and paired preference designs
Sucking & leg kicks
–
Response contingencies
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Types of observational research
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Quasi-experimental
–
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differences in naturally occurring groups
Observational –
Differences in naturally occurring conditions

Complementary, not exclusive

Is age (development) studied
experimentally or observationally?
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Observational

Quasi-experiment
–
Between subject exploration
of differences in naturally
occurring groups
S o lo O p e n M o u th S m ilin g b y G a z in g a t M o th e r
 Drug

Observational
–
Differences in naturally
occurring conditions
 Gazing
at mother versus
gazing away
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0 .8
P ro p o rtio n o f O p e n M o u th S m ilin g O n ly
exposure, breast-feeding,
and attachment groups
F ig u re 2 b .
0 .7
0 .6
0 .5
0 .4
0 .3
0 .2
0 .1
0 .0
Predicted or dependent variables
Experimental and all observational
approaches measures variables
 Variable - a measurable component of
behavior or physiological functioning that
can take on different values
 Not all aspects of behavior or physiology by
specific feature of interest

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Qualitative methods
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Intensive description in regular language
–
Not measuring variables

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Pro: Insight into individual and developmental
process
–

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E.g., baby biography, one infant described over time
Emerged with romantic emphasis on individual
Con: Not generalizable
Complementary, not exclusive
–
Role in empirical project
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Which is best?
Longitudinal or cross-sectional
 Experimental, observational, or qualitative?

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Observing behavior
Observed on-line or video-recorded
 Measured with

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–
–
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Trait rating - global judgement
Time sampling
Event sampling (frequency)
Event sampling (duration)
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Time-sampling & event-sampling
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Physiological measures

Heart rate & respiration (video)
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Electroencephalogram
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Relative lateral activation during crying
Actigraphy
–

avoidant infants, infants on visual cliff
Index of ADD?
Increasingly important supplement to
behavioral measures
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Adequacy of measures

Reliability
–
Consistency of measurement
 Inter-rater

reliability of observations
Bias
–
Systematic impact of unmeasured variables
 Blinding
in drug studies
 Keeping observations independent
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Validity

Are we measuring what we think we’re
measuring,
–
–
Do the variables measured the constructs
mentioned in the research questions?
There is no final answer
 Reunion
behavior = Attachment?
 Smiling = Joy?
 Looking = Preference?
 Heart rate = Arousal?
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References
Infancy (Fogel)
 Development in infancy (Lamb, Bornstein,
& Teti)
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Development: Definition and methods