Developmental Theory & Hypotheses (devpsych-theory-and-hypotheses)

Developmental Psychology rewards a theory of change and age-graded, directional hypotheses. Because the journal asks for a credible developmental claim and applies JARS reporting, the cardinal rule is: state the developmental mechanism and the predicted form of change before the data, and label exploratory analyses as exploratory.

When to trigger

• Writing the theoretical framing and hypotheses
• Preparing a preregistration / pre-analysis plan for a developmental study
• Reconciling what you predicted about change with what the trajectories show
• A reviewer flagged the work as "atheoretical," "not developmental," "post hoc," or "HARKed"

Build the developmental argument

1. State the mechanism of change. What developmental process (maturation, learning, transactional parent–child dynamics, scaffolding, cumulative risk) predicts the effect, and why it changes with age.
2. Specify the form of the developmental hypothesis. Be explicit about which of these you predict: an age main effect, an age × condition interaction, a growth-curve shape (slope sign, acceleration), a within-person change, or a moderated trajectory.
3. Derive directional predictions. Give a sign and, where possible, a magnitude/effect-size expectation — not "age will be related to X."
4. Mark hypothesis status. Separate confirmatory (preregistered, predicted) from exploratory (generated after seeing data) analyses, clearly, per JARS.
5. State what would disconfirm the developmental account — e.g., a flat trajectory, a reversed age slope, or invariance failure that means the construct is not the same across ages.

Age-graded hypothesis forms (name yours)

Worked micro-example — theory to hypothesis status (illustrative)

A longitudinal effortful-control package, written so the developmental claim and status are legible.

Mechanism: Sensitive, contingent parenting scaffolds the maturation of
           effortful control; the scaffolding payoff grows across early childhood.
H1 (confirmatory, preregistered): Effortful control shows positive
           within-person growth from age 4 to 8 (latent slope > 0).
H2 (confirmatory): Maternal scaffolding at wave 1 predicts a steeper slope
           (scaffolding × time interaction, directional).
H3 (exploratory): Bidirectional child→parent effects across waves
           (RI-CLPM) — labeled exploratory; preregister for a future sample.
Disconfirming: a flat/negative latent slope, or measurement non-invariance
           across ages (the construct is not the same thing being "grown").

Avoiding HARKing in developmental work

• Do not present an unexpected age interaction or a trajectory shape you discovered post hoc as if it had been predicted. If you found it after seeing the data, say so and frame it for confirmation.
• Constraints on generality matter here: name the ages, populations, and cohort/era to which the developmental claim is meant to apply, rather than implying it holds at every age and place.

Theory-stage reviewer pushback and the venue fix

Anti-patterns

• Hypotheses about a relationship "in children/older adults" with no change component
• Non-directional "age will be associated with X" predictions
• Blurring confirmatory and exploratory analyses (JARS expects the split)
• Ignoring that an effect could be cohort, not age, and theorizing as if it were maturation
• No statement of what trajectory or interaction would disconfirm the account

Output format

【Mechanism of change】the developmental process, briefly
【Developmental hypothesis form】age effect / age×condition / growth shape / within-person / moderated
【Hypotheses】directional, testable (H1, H2, …)
【Status】confirmatory (preregistered) vs exploratory
【Disconfirming evidence】trajectory/interaction/invariance result that counts against it
【Next】devpsych-literature-positioning

Supplementary resources

• ../../resources/external_tools.md — preregistration templates and developmental-theory references
• ../../resources/official-source-map.md — JARS reporting standards and scope