Messinger Development: Definition & methods of study

Messinger Overview n Defining development n Studying development – Longitudinal & cross-sectional designs n Study design – Experimental, observational, and qualitative studies n Predicted variables – typically behavior and/or physiologic activity

Messinger Development defined n Individual change that is, normative, non- reversible, relatively stable, and sequential.

Messinger Development defined defined n Normative process – everyone’s doing it n non-reversible – reorganization of the entire person n relatively stable – you can’t go back, n sequential change – crawl before you walk n Examples

Messinger Is development n Increasing functionality in all things? – Loss of perceptual acuity in non-native languages – Old-age n Headed toward a goal? – Development has normative outcomes, – but time goes forward – prior events cause subsequent events n not the opposite

Messinger Canalization (Waddington)

Messinger Overview n Studying development – Longitudinal and cross-sectional n Studying behavior – Experimental and observational n Studying outcomes – Behavior and physiology n Relate to your article reviews and final projects

Messinger Longitudinal n Same infants over time n Pro: Answers ‘How do individuals change in time?’ n Con: Takes a long time – Attrition n Final project examples?

Messinger Cross-sectional n Different infants at different times n Pro: Efficient, large numbers of subjects n Con: Differences do not necessarily reflect individual’s development – e.g. cohort n Final project examples?

Messinger Longitudinal vs. cross-sectional n Development is relatively stable on large time scales – Motor, physical, emotional, communicative n But choppy on smaller scales – Only longitudinal research can show this n Emergent order from chaotic, dynamic systems n Previous example?

Messinger Hypothetical applied example from Lamb et al.

Messinger Individual differences

Messinger Complementary, not exclusive n A single study can combine longitudinal and cross-sectional methods n Some infant studies use neither method – They look at behavior at one point in time n E.g., Neonate study

Messinger Predictor and predicted variables n In developmental studies, – age is a predictor – behavior or physiology are predicted n Experimental and observational studies

Messinger Stability and continuity n Stability – Rank of individual in group is stable n Continuity – Level of behavior is continuous across ages

Messinger Experiments are unique because n They can demonstrate causality n How?

Messinger Experimental design n Between subject – A treatment (independent variable) is assigned randomly – creating treatment and control groups n Within-subject – All infants get treatment and control – Examples n Rating study, Face-to-face still-face

Messinger Constrained behavior in experiments n Gazes at stimulus – habituation and paired preference designs n Sucking & leg kicks – Response contingencies

Messinger Types of observational research n Quasi-experimental – differences in naturally occurring groups n Observational - – Differences in naturally occurring conditions n Complementary, not exclusive n Is age (development) studied experimentally or observationally?

Messinger Observational n Quasi-experiment – Between subject exploration of differences in naturally occurring groups n Drug exposure, breast-feeding, and attachment groups n Observational – Differences in naturally occurring conditions n Gazing at mother versus gazing away

Messinger Predicted or dependent variables n Experimental and all observational approaches measures variables n Variable - a measurable component of behavior or physiological functioning that can take on different values n Not all aspects of behavior or physiology by specific feature of interest

Messinger Qualitative methods n Intensive description in regular language – Not measuring variables n E.g., baby biography, one infant described over time n Pro: Insight into individual and developmental process – Emerged with romantic emphasis on individual n Con: Not generalizable n Complementary, not exclusive – Role in empirical project

Messinger Which is best? n Longitudinal or cross-sectional n Experimental, observational, or qualitative?

Messinger Observing behavior n Observed on-line or video-recorded n Measured with – Trait rating - global judgement – Time sampling – Event sampling (frequency) – Event sampling (duration)

Messinger Time-sampling & event-sampling

Messinger

Physiological measures n Heart rate & respiration (video) – avoidant infants, infants on visual cliff n Electroencephalogram – Relative lateral activation during crying n Actigraphy – Index of ADD? n Increasingly important supplement to behavioral measures

Messinger Adequacy of measures n Reliability – Consistency of measurement n Inter-rater reliability of observations n Bias – Systematic impact of unmeasured variables n Blinding in drug studies n Keeping observations independent

Messinger Validity n 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 n Reunion behavior = Attachment? n Smiling = Joy? n Looking = Preference? n Heart rate = Arousal?

Messinger References n Infancy (Fogel) n Development in infancy (Lamb, Bornstein, & Teti)