theoryforge: A theory you can check

Treat the Theory as a Checked Document

Structural validation checks required fields and allowed values. Full validation also follows identifiers across the document, so a prediction cannot claim to derive from a proposition that does not exist. The function returns silently when the document passes and stops with a list of the errors when it fails.

tf_validate(switching, full = TRUE)

check <- tf_check(switching)
c(score = check$aggregate_score,
  gate = check$gate,
  blockers_failed = check$n_blockers_failed)

#>           score            gate blockers_failed 
#>          "85.1"          "pass"             "0"

The checklist has 12 items, each tied to a source in the methodological literature. They cover features that make a theory appraisable, such as whether it states what it prohibits, whether its predictions derive from stated propositions, and how precise and risky those predictions are (e.g., Meehl, 1990). Two of the items are blockers, and the gate passes only if neither fails. The score, a weighted total out of 100, measures how completely the theory is specified. A well-specified theory can still be wrong, while a promising informal account can score poorly because it is not yet explicit enough to test.

Read the Graph

The theory’s propositions form a causal graph. Because the source is structured data, the same graph can be rendered for a reader, as in Figure 1, or exported for another program.

flowchart TB
  c_sensorimotor_experience["Sensorimotor experience<br>with a concept"]
  c_modality_activation["Modality-specific<br>perceptual activation"]
  c_switch_cost["Cost of switching modality<br>between consecutive trials"]
  c_conceptual_access["Ease of conceptual access"]
  c_lexical_familiarity["Lexical familiarity with<br>the word form"]
  c_sensorimotor_experience -->|increases| c_modality_activation
  c_modality_activation -->|increases| c_switch_cost
  c_modality_activation -->|increases| c_conceptual_access
  c_lexical_familiarity -->|increases| c_conceptual_access

Figure 1: The Constructs of the Theory and the Arrows It Asserts Between Them, as theoryforge Reads Them From the File.

An acyclic causal graph also implies conditional independencies. Each one names an association that should be absent if the graph is correct, either outright or once certain constructs are held constant. Together, these claims define what the theory forbids in observed data.

The graph contains four arrows and entails six testable independencies. These six form a basis set, so every other independence the graph implies follows from them. The most discriminating one is that sensorimotor experience and lexical familiarity should be uncorrelated, because the only path between them is blocked by a collider at conceptual access. An observed correlation between the two, with nothing conditioned on, would count against the graph.

Give the Claims a Discriminating Test

To test these claims, I simulated two data sets of 4,000 observations each. One follows the theory’s graph, and the other follows a rival account in which sensorimotor experience also contributes to lexical familiarity, with every other path unchanged. In each data set, I assessed all six independencies with the linear conditional-independence tests in the dagitty package (Textor et al., 2016). Table 1 shows how the key claim fares in both.

All six implied independencies are compatible with the data generated from the theory. In the data generated from the rival, only the claim shown in Table 1 fails. There, sensorimotor experience and lexical familiarity are substantially correlated, while the estimates for the other five claims stay close to zero. The failure therefore locates the part of the graph that conflicts with the data, a diagnosis that no single global score could give.

Preserve the Result With the Theory

The dossier gathers the rigour checklist, the severity of each prediction, the theory’s provenance and a preregistration of its hypotheses into one Markdown record. The R and Python packages produce the same dossier for the same theory, so a checksum of that record identifies the audited state of the theory in either language. Table 2 repeats the score and gate and shows the first 12 characters of the SHA-256 checksum.

Limits

Formalisation moves judgement into the open without removing it. Researchers still decide which constructs and arrows belong in the graph, how the constructs are measured, and whether an observed departure matters scientifically. The theory document records where each of those judgements enters. The checklist screens the structure and wording of a specification, so it cannot tell whether the constructs themselves are well chosen. Theories with feedback loops also need methods beyond the conditional-independence analysis used here, because theoryforge derives implications only from acyclic graphs.