Transcript Development: Definition and methods

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
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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
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crawl before you walk
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Examples
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Is development
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Increasing functionality in all things?
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Loss of perceptual acuity in non-native
languages
Old-age
Headed toward a goal?
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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
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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
–
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Attrition
Final project
examples?
120
110
Bayley Cognitive Score
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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
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Different infants at
different times
Pro: Efficient, large
numbers of subjects
Con: Differences do
not necessarily reflect
individual’s
development
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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
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Development is relatively
stable on large time scales
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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
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A single study can combine longitudinal
and cross-sectional methods
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Some infant studies use neither method
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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,
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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
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Level of behavior is continuous across ages
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Experiments are unique because
They can demonstrate causality
 How?
Estimated Marginal Means
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Estimated Marginal Means of MEASURE_1
.16
.14
.12
.10
.08
.06
EXP2
.04
Comparison
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Exposed
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SMILES
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Experimental design
Between subject
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A treatment (independent variable) is
assigned randomly
creating treatment and control groups
Within-subject
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All infants get treatment and control
Examples
 Rating
Estimated Marginal Means
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study, Face-to-face still-face
Estimated Marginal Means of MEASURE_1
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.14
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.06
EXP2
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Comparison
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Exposed
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SMILES
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Constrained behavior in
experiments
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Gazes at stimulus
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habituation and paired preference designs
Sucking & leg kicks
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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
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Complementary, not exclusive
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Is age (development) studied
experimentally or observationally?
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Observational
Quasi-experiment
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Between subject exploration
of differences in naturally
occurring groups
 Drug
exposure, breast-feeding,
and attachment groups
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Observational
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Differences in naturally
occurring conditions
 Gazing
at mother versus
gazing away
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Figure 2b.
Solo Open Mouth Smiling by Gazing at Mother
0.8
Proportion of Open Mouth Smiling Only
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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
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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
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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
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Heart rate & respiration (video)
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Electroencephalogram
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Relative lateral activation during crying
Actigraphy
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avoidant infants, infants on visual cliff
Index of ADD?
Increasingly important supplement to
behavioral measures
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Adequacy of measures
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Reliability
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Consistency of measurement
 Inter-rater
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reliability of observations
Bias
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Systematic impact of unmeasured variables
 Blinding
in drug studies
 Keeping observations independent
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Validity
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Are we measuring what we think we’re
measuring,
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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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