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Development:Definition & methods of study

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Overview

Defining development Studying development

– Longitudinal & cross-sectional designs Study design

– Experimental, observational, and qualitative studies

Predicted variables– typically behavior and/or physiologic activity

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Development defined

Individual change that is, normative, non-reversible, relatively stable, and sequential.

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Development defined defined

Normative process – everyone’s doing it

non-reversible– reorganization of the entire person

relatively stable– you can’t go back,

sequential change– crawl before you walk

Examples

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Is development

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 – Longitudinal and cross-sectional

Studying behavior– Experimental and observational

Studying outcomes– 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?

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YearM = 93.5n = 200

YearsM = 79.1n = 190

YearsM = 82.1n = 132

Typical Trajectory:Cognitive Scores Decline

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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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DifferentIndividuals

OneYearTwoYearThreeYear

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Longitudinal vs. cross-sectional

Development is relatively stable on large time scales– Motor, physical, emotional,

communicative But choppy on smaller scales

– 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

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?

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Comparison

Exposed

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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 study, Face-to-face still-face

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Comparison

Exposed

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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 exposure, breast-feeding, and attachment groups

Observational– Differences in naturally

occurring conditions Gazing at mother versus gazing

away

Figure 2b.

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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

E.g., baby biography, one infant described over time

Pro: Insight into individual and developmental process– 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

– 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)– avoidant infants, infants on visual cliff

Electroencephalogram– Relative lateral activation during crying

Actigraphy– 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)