The Development of Tool Use in Infancy

Talk OverviewBackground: Understand infant cognitive developmentThe Problem of Tool Use:

What is requiredWhat develops

Mechanisms of Development: Behavioural schemas (Six mechanisms)Representations (Redescription) Linking Two tracks

Reflection, and Direction for Roboticists

Psychology Robotics research

Timeline of Development

Birth 6 9 12 15 18 24 months

Free Play: stereotypical accommodative relational simple relational functional relational

Overlapping waves (Siegler)

Timeline of Development

Free Play: stereotypical accommodative relational

Problem solving: support string stick radial grasp shapes in slots

Birth 6 9 12 15 18 24 months

simple relational functional relational

Two essential aspects always present Play: vary situations, performance, discover how it works Problem Solving: discover means good for particular goals

The Problem of Tool Use Selecting the right tool or tools Spatially arranging the right relationships

(between tools and target objects) Performing the appropriate manipulations Degrees of Freedom Solve by

Forward Search Forward Search with Heuristics Means-end

What Develops in Infants? Planning seems to be present early

Some improvements in Memory, Backtracking, Inhibition

Development of Schemas (≈ Planning Operators) Sensorimotor Schema

Development of Representations Objects Space, spatial relationships Actions ….

2

1

What Develops in Infants? Planning seems to be present early

Some improvements in Memory, Backtracking, Inhibition

Development of Schemas (≈ Planning Operators) Sensorimoto

Development of Representations Objects Space, spatial relationships Actions ….

2

1

Mechanisms M1 Repetition M2 Variation and selection M3 Differentiation M4 Composition M5 Modularisation M6 Decomposition

Mechanisms M1 Repetition M2 Variation and selection M3 Differentiation M4 Decomposition M5 Composition M6 Modularisation

Opportunistic

Where schema can Leads to discoveries (affordance) (play)

Mechanisms M1 Repetition M2 Variation and selection M3 Differentiation M4 Decomposition M5 Composition M6 Modularisation

Parameter variation Understand effects Generate new results Especially at difficulty Transition periods

Mechanisms M1 Repetition M2 Variation and selection M3 Differentiation M4 Decomposition M5 Composition M6 Modularisation

Branching in behaviour graph

Unexpected result Find preconditions Adjust motor action

Branching in behaviour graph

Mechanisms M1 Repetition M2 Variation and selection M3 Differentiation M4 Decomposition M5 Composition M6 Modularisation

Borrowed movement too crude

Refine parts Flexible reassembly

Mechanisms M1 Repetition M2 Variation and selection M3 Differentiation M4 Decomposition M5 Composition M6 Modularisation

Behaviour graph (join)

Simple sequence Hierarchical control

Mechanisms M1 Repetition M2 Variation and selection M3 Differentiation M4 Decomposition M5 Composition M6 Modularisation

Refine by repetition, variation and selection, produce a “smooth atom”

Ready to be used as subunit (for ongoing development)

Behaviour graph (join)

Stereotypical (Without Objects)1. Arm wave (100%): rapid flapping from shoulder

(surface slapping, waving objects/banging)

2. Finger flex (100%); flexion and extension of all four fingers

( exploratory behaviours with objects)

3. Hand rotate (90%) and flex (80%): a rhythmic rotation, bending and extending of the wrist

(object exploration?)

4. Clap hands together (75%)

( banging objects together) (85%)

5. Finger rotate (15%): similar to turning a large dial

(rotation of lids/dials?)

Single Objects Reach + Grasp Developing the Stereotypical

Behaviours with Objects: Waving a rattle Catch/release or scratch or squeezing an object, or crushing (e.g. paper)

(differentiation (M3), variation and selection (M2)) Multi-sensory Object Exploration Hand-Surface interaction

Object-Object Object-surface object-object Obstacle removal Support String Lever Stick ( the magic happens here ) Fitting Shapes into Slots (peg-in-hole task) Spoon-feeding (and other objects with handles)

Reinforcement learning

Timeline of Development

Free Play: stereotypical accommodative relational

Problem solving: support string stick radial grasp shapes in slots

Birth 6 9 12 15 18 24 months

simple relational functional relational

Overlapping waves (Siegler)

Really interesting part

stereotypical single object object-object

DONE

Representations (Objects, Space, …) Transfer as a proxy

Brown: Level of representation rather than age

determines transfer efficiency

Representations (Objects, Space)1. Coarse to Fine• Some situations generalise very well, and immediately • Sometimes over-generalise

(scale errors, incompatible shapes)

2. Context Specific to General3. Integration of Fragmentary Representations

Representations (Objects, Space)1. Coarse to Fine2. Context Specific to General• Some situations, do not generalise well at all• Spoon for self-feeding,

or for directing to another object• hand in a slot vs. posting a disk

3. Integration of Fragmentary Representations

Representations (Objects, Space)1. Coarse to Fine2. Context Specific to General1. Integration of Fragmentary Representations

“perception leads to multiple representations that may be recruited for different tasks”

4-month-olds perceive 3D form of rotating wireframes 6-month-olds “complete” solid 3D objects 18-month-olds still use fragmentary representations 24-month-olds 3D whole-object geometric representations

Advantages of fragmentary / task specific representations:• Simple space which for particular task• When another seems more appropriate

switch representation

Linking TracksSensorimotor

& Representation

MOVING OF MOUTH

EDGES

MOVING OF CONTAINER

EDGES

Container(object)

Push(action)

inside(spatial relationship)

Higher orderconcept

broken(object state)

Reflection 1. Planning present early, but few schemas (planning operators)

2. Initial Knowledge is Fragmentary and Incomplete

“to understand is to invent”, + schedule

3. Infants Learn Slowly, but Thoroughly

representations slow to change

4. Generalisation Depends on Representation

What are infants good and bad at? Good: build on what they know, try out, refine, assimilate Bad: make big leaps take several months

Emulating in a Robot…1. Start with Few Schemas, to Get a Lot

(Crucial to implement the Mechanisms)

2. Representations Must Develop Gradually

3. Interaction Between the Concrete and Abstract Tracks Difficult but Crucial (structural bootstrapping) Addressing the main mystery of development

4. Guiding Examples and Benchmarks for Development

Advancing the ScienceMany take “inspiration” from infants:

Affordances, intrinsic motivation, play

Need to: Model whole development, e.g. from 6 to 18 months

Aim for Same Behaviour How do they explore a space? How is old knowledge re-used? How robust is the behaviour? Representation

Psychology Robotics

Advancing the Science

Modelling:

Means-end behaviours

XXX

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Experiments:

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