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
–

non-reversible
–
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reorganization of the entire person
relatively stable
–

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
–

Studying behavior
–
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Experimental and observational
Studying outcomes
–

Longitudinal and cross-sectional
Behavior and physiology
Relate to your article reviews and final
projects
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Longitudinal


Same infants over
time
Pro: Answers ‘How do
individuals change in
time?’
Con: Takes a long time
–

Attrition
Final project
examples?
120
110
Bayley Cognitive Score

Typical Trajectory:
Cognitive Scores Decline
100
90
80
70
60
50
1
Year
M = 93.5
n = 200
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2
Years
M = 79.1
n = 190
3
Years
M = 82.1
n = 132
Cross-sectional



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

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

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
–

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?
Estimated Marginal Means

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
Estimated Marginal Means

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
–

habituation and paired preference designs
Sucking & leg kicks
–
Response contingencies
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Types of observational research

Quasi-experimental
–

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
 Drug

Observational
–
Differences in naturally
occurring conditions
 Gazing
at mother versus
gazing away
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0.8
Proportion of Open Mouth Smiling Only
exposure, breast-feeding,
and attachment groups
Figure 2b.
Solo Open Mouth Smiling by Gazing at Mother
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

Intensive description in regular language
–
Not measuring variables


Pro: Insight into individual and developmental
process
–


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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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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