[DSRP Evidence](https://dsrpevidence.org/)

# Infants' understanding of the causal power of agents and tools

## Details

**Authors** Adibpour & Hochmann

**Year** 2023

**Publisher** Proceedings of the National Academy of Sciences (PNAS)

**Discipline** Psychology

[Read it at the publisher](https://doi.org/10.1073/pnas.2309669120) 
10.1073/pnas.2309669120

## In authors' words

### Abstract

Tools are objects that are manipulated by agents with the intention to cause an effect in the world. We show that the cognitive capacity to understand tools is present in young infants, even if these tools produce arbitrary, causally opaque effects. In experiments 1–2, we used pupillometry to show that 8-mo-old infants infer an invisible causal contact to account for the—otherwise unexplained—motion of a ball. In experiments 3, we probed 8-mo-old infants’ account of a state change event (flickering of a cube) that lies outside of the explanatory power of intuitive physics. Infants repeatedly watched an intentional agent launch a ball behind an occluder. After a short delay, a cube, positioned at the other end of the occluder began flickering. Rare unoccluded events served to probe infants’ representation of what happened behind the occluder. Infants exhibited larger pupil dilation, signaling more surprise, when the ball stopped before touching the cube, than when it contacted the cube, suggesting that infants inferred that the cause of the state change was contact between the ball and the cube. This effect was canceled in experiment 4, when an inanimate sphere replaced the intentional agent. Altogether, results suggest that, in the infants’ eyes, a ball (an inanimate object) has the power to cause an arbitrary state change, but only if it inherits this power from an intentional agent. Eight-month-olds are thus capable of representing complex event structures, involving an intentional agent causing a change with a tool.

### What they set out to do (purpose)

To test whether 8-month-olds represent the causal power of agents and that agents can transfer it to tools.

### What they found (results)

Via pupillometry, 8-month-olds showed surprise when an intentional agent's launch failed to cause a cube's change, but no such expectation for an inanimate launcher — attributing causal power to agents and their tools.

## Commentary

### In short

Infants relate events as action and reaction (causal power).

### In more detail

Preverbal infants build causal relations between events, attributing an action's power to produce a reaction even through an intermediary tool. Purpose: To test whether 8-month-olds represent the causal power of agents and that agents can transfer it to tools. Finding: Via pupillometry, 8-month-olds showed surprise when an intentional agent's launch failed to cause a cube's change, but no such expectation for an inanimate launcher — attributing causal power to agents and their tools. [Added 2026-07-30 as new evidence beyond the original 109; DSRP structural basis: R axiom (Action–Reaction Dyad): the study is about attributing an action's power to produce a reaction — the core a→r relationship.]

**Patterns it shows** R

**Added** 2026-07-30

**How to cite this** Adibpour & Hochmann (2023). Infants' understanding of the causal power of agents and tools. Proceedings of the National Academy of Sciences (PNAS).