Demonstration

Exploring how learners extend verb meanings when features are added or removed.

Research Questions

Minimal Subtraction in Verb Learning:

When participants learn two verbs — one with 2 semantic features and one with 4 features (a superset of the first) — and are then shown an action described by 3 features (intermediate between the two), which verb do they extend to cover it?

Will learners map the 3-feature action to the 4-feature verb (missing only 1 feature) rather than the 2-feature verb (which has 1 unexpected extra)?

Minimal subtraction hypothesis predicts: The 4-feature (specific) verb will be extended.
Alternative hypothesis: TODO (currently reading up on prototype theory)

Design Summary

Component	Description
Two Verbs	General Verb: 2 base features (e.g., PATH + MANNER \| RESULT)
Two Verbs	Specific Verb: 4 features = same 2 base features + 2 additional features (e.g., PATH + MANNER + RESULT + RESULT2 \| MANNER2)
Nouns	Nouns: Unique shape-colour combinations. Each verb paired with {x} nouns
Training Exposures	Participants see each verb-noun pairs, showing all defining actions of the verb
Training heck	2AFC (two-alternative forced choice): Correct verb animation vs. same verb with one misspecified feature (e.g., wrong PATH direction)
Critical Test	Show action with 3 features (PATH + MANNER + RESULT). Participant chooses between the 2-feature verb or the 4-feature verb?

Stimuli Overview

Four shapes for the 4 nouns (2 nouns per verb). Each shape is paired with a unique color.

Randomized pairing of shapes and colors by participant.

Example Nouns

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Example Verbs with Different Feature Requirements

The experiment uses two novel verbs that share 2 base features but differ in specificity.

Verb Type	Features	Description
General Verb (2 features)	PATH	Directional movement
General Verb (2 features)	MANNER	How the shape moves (spinning)
Specific Verb (4 features)	PATH	Same direction as general verb
	MANNER	Same manner as general verb
	RESULT	End-state change (fading)
	RESULT2	Diagonal stripe pattern overlay

Counterbalancing

Nonce word labels for verbs and nouns are randomly assigned to each participant from a fixed word bank. The single between-subjects counterbalancing factor concerns the identity of the 4th feature of the specific verb during training.

The critical test scene (PATH + MANNER + RESULT) is identical across conditions. Conditions A and B differ only in which feature class is subtracted, allowing assessment of whether extension toward the specific verb is modulated by the type of absent feature (result vs. manner). Since path/manner/result feature values are drawn randomly per participant, condition assignment is the only systematic between-subjects factor.

Condition	General Verb	Specific Verb	Critical Test Scene	Feature Subtracted at Test
A	PATH + MANNER	PATH + MANNER + RESULT + RESULT2	PATH + MANNER + RESULT	RESULT2 (a second result feature)
B	PATH + MANNER	PATH + MANNER + RESULT + MANNER2	PATH + MANNER + RESULT	MANNER2 (a second manner feature)

Training Exposure

A 2-alternative forced choice (2AFC) task confirms that participants have learned the verb meanings. On each trial, participants see the target verb paired with either the correct animation or a foil animation in which one feature is misspecified (e.g., incorrect PATH direction). A performance criterion TBD (e.g., ≥80% correct) gates entry into the test phase.

General verb: Always shows 2 features (PATH + MANNER)

Specific verb: Always shows all 4 features (PATH + MANNER + RESULT + RESULT2)

The specific verb is a strict superset of the general verb's features. This ensures that any decision isolates the role of the additional features rather than differences in the base representation.

Participants advance with spacebar; replay is available for clarity.

Example Training Stimuli

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Training Attention Check (2AFC)

After training blocks, we probe verb knowledge using 2-alternative forced choice (2AFC). Participants see two animations side-by-side and choose which one correctly shows the named verb.

Format: One animation is correct, the other has one misspecified feature (e.g., PATH direction is wrong).

2AFC Examples

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Critical Test Trials

Minimal Subtraction Hypothesis: When shown a 3-feature action (PATH + MANNER + RESULT), participants will choose the verb that requires the minimal change:

The action is missing only 1 feature from the specific verb (RESULT2 is absent)
The action has 1 extra feature beyond the general verb (RESULT is extra)

Critical Trial Format

Test stimulus: An action with 3 features (PATH + MANNER + RESULT, no RESULT2)

Question: "What are they doing? OPtions: [general_verb] or [specific_verb]"

Prediction: Participants should choose the specific verb (4 features) over the general verb (2 features)

Example Critical Test Trial

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Concerns

1. Establish the Basic Subtraction Effect First?

it would be prudent to first establish the basic minimal subtraction effect in a simpler case, for e.g., a 4-feature vs. 5-feature contrast with a 3-feature critical test scene. Here, the critical decision is between subtracting 1 feature or 2 features.

2. Statistical Power

The critical test is currently a single binary forced-choice trial per participant. We could add multiple critical test trials per participant deleting different feature values??.

3. Learnability of the 4-Feature Verb

The specific verb the specific verb requires participants to encode and retain four distinct semantic features from a small number of training exposures. Would two training nouns be sufficient for participants to reliably discriminate all four features?.