Individual differences in the forms of personality trait trajectories

Area of Science:

• Psychology
• Developmental Psychology
• Quantitative Psychology

Background:

• Personality change is often modeled assuming a single trajectory form for all individuals.
• This assumption is untested and may not reflect the complexity of personality development.
• Existing models estimate deviations but don't test for differing trajectory forms.

Purpose of the Study:

• To empirically test the extent of variation in best-fitting personality development trajectory forms across individuals.
• To investigate if heterogeneity in trajectory forms is associated with the amount and type of personality change.
• To examine factors associated with differing trajectory forms and discrepancies between individual- and sample-level models.

Main Methods:

• Analysis of four large longitudinal datasets (N = 26,469; Mage = 47.55).
• Empirical testing of individual-level best-fitting model forms for Big Five personality development.
• Examination of associations between trajectory form type, change amounts, and demographic/trait variables.

Main Results:

• Substantial heterogeneity was found in the best-fitting trajectory forms across individuals and datasets.
• The type of trajectory form was directly associated with the net and total amount of personality change over time.
• Using a single, worse-fitting model form led to significant misquantification of personality changes.
• Gender, age, trait levels, and data collection waves were associated with individual trajectory form types.
• Significant discrepancies arose from comparing individual-level best-fitting forms with sample-level models and alternative modeling choices.

Conclusions:

• Individuals exhibit significant variation in their personality development trajectory forms.
• A flexible, person-level approach is necessary for accurately understanding personality change processes.
• Ignoring individual differences in trajectory forms can lead to substantial misinterpretations of personality development.