Experimental paradigms

Separating world knowledge from factivity

A key challenge in studying factivity is that our judgments about whether someone is certain of a proposition depend on two factors:

  1. The properties of the predicate (whether speakers interpret it as being associated with a presupposition)
  2. Our world knowledge about how likely the proposition is

Degen and Tonhauser (2021) developed a two-stage experimental design to tease these apart:

Stage 1: Norming study (Experiment 2a)

First, they measured how world knowledge affects belief in various propositions. Participants saw items like:

Norming item example

Fact: Sophia is a hipster.
Question: How likely is it that Sophia got a tattoo?
Response: [slider from 0 to 1]

For each proposition (e.g., Sophia got a tattoo), they created two contexts–one making it more likely (Sophia is a hipster) and one making it less likely (Sophia is a Mormon). This gives us a measure of world knowledge independent of any embedding predicate.

Stage 2: Projection study (Experiment 2b)

Next, they embedded these same propositions under various predicates and asked about the speaker’s certainty:

Projection item example

Context: Isabella said that Sophia is a hipster.
Utterance: Noah knows that Sophia got a tattoo.
Question: Is Noah certain that Sophia got a tattoo?
Response: [slider from 0 to 1]

They reasoned that, if speakers categorically interpret know as triggering a factive presupposition, Noah should be certain regardless of the prior probability; but, they reasoned, if projection is gradient, his certainty should vary with world knowledge.

Key experimental details

The experiments tested 20 predicates that theory suggests might pattern differently:

  • Canonical factives: be annoyed, discover, know, reveal, see
  • Non-factives:
    • Non-veridical non-factive: pretend, say, suggest, think
    • Veridical non-factive: be right, demonstrate
  • Optionally factive: acknowledge, admit, announce, confess, confirm, establish, hear, inform, prove

Each participant saw 20 items (one per predicate) plus controls, with predicates paired with different complement clauses and prior contexts across participants.

References

Degen, Judith, and Judith Tonhauser. 2021. “Prior Beliefs Modulate Projection.” Open Mind 5 (September): 59–70. https://doi.org/10.1162/opmi_a_00042.