Chapter 1. Imitation: Thoughts about Theoriesin Imitation and Social Learning in Robots, Humans and Animals,

Nehaniv and Dautenhaln.

Course: Robots Learning from Humans

Geonmo Gu

Computer Theory and Application LaboratorySchool of Computer Science and Engineering

http://theory.snu.ac.kr

Soojin Jung

Cognitive PsychologyDepartment of Cognitive Science

Contents Introduction

The Correspondence Problem

Three theories Active Intermodal Mapping (AIM) Goal-Directed Imitation (GOADI) Associative Sequence Learning (ASL)

Contrasting 3 theories Issue 1: Effect-dependency Issue 2: Awareness

Questions for ASL model: about Intention

Conclusion & Discussion

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Introduction Imitation as Transferred information between Agents (biological, computational or

robotic autonomous systems). Challenge in imitation theory:

HOW observation of action facilitates production of matching movements.

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The Correspondence Problem The problem for one individual of producing behaviour that matches with behavior it

observes in another. The observer must formulate motor commands to match visual input

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Observer Model

Visual Input

The Correspondence Problem The problem for one individual of producing behaviour that matches with behavior it

observes in another. The observer must formulate motor commands to match visual input

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Observer Model

Visual Input

The Correspondence Problem The problem for one individual of producing behaviour that matches with behavior it

observes in another. The observer must formulate motor commands to match visual input

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Model

Motor command

Observer

The Correspondence Problem

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Observer ModelObserver Model

Visual Input

Visual information

Observer has Visual Information of model’s action Motor information (feeling) of observer’s action

The Correspondence Problem Observer has

Visual Information of model’s action Motor information (feeling) of observer’s action

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Observer ModelObserver Model

Visual Input

NO Visual informationVisual information

The Correspondence Problem Observer has

Visual Information of model’s action Motor information (feeling) of observer’s action

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Observer ModelObserver Model

Visual Input

Motor information (feeling)Visual information

The Correspondence Problem Observer has

Visual Information of model’s action Motor information (feeling) of observer’s action

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ObserverModel

Motor information (feeling)Visual information

feeling

3 Theories on Imitation 1. Active Intermodal Mapping (AIM) 2. Goal-Directed Imitation (GOADI) 3. Associative Sequence Learning (ASL)

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<AIM> <GOADI> <ASL>

3 Theories on Imitation 1. Active Intermodal Mapping (AIM) 2. Goal-Directed Imitation (GOADI) 3. Associative Sequence Learning (ASL)

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<AIM> <GOADI> <ASL>

1. Active Intermodal Mapping (AIM) Visual representation Motor representation Supramodal representation

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ObserverModel

Motor representationVisual representation

feeling

Supramodal representation

Organ relation

1. Active Intermodal Mapping (AIM) Visual information: adult’s tongue-protrusion Motor information: infant’s feeling Organ relation: tongue-beyond-lips

Organ: part of body. head, brows, tongue, lips

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Facial imitation

Tongue-beyond-lips

1. Active Intermodal Mapping (AIM) Correspondence problem

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3 Theories on Imitation 1. Active Intermodal Mapping (AIM) 2. Goal-Directed Imitation (GOADI) 3. Associative Sequence Learning (ASL)

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<AIM> <GOADI> <ASL>

2. Goal-Directed Imitation The GOADI theory of imitation suggests that perceived actions are decomposed into a

series of ‘aspects’. Only some goal aspects are imitated; movement end-points and the manipulation of

objects are more likely to be imitated than either the effector or the movement path.

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2. Goal-Directed Imitation Correspondence problem:

No special relationship between matching movements under GOADI. Goal imitation: if the movement most commonly associated with the perceived goal is

different from the movement of the model, then goal, but not movement, imitation will occur.

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Perceived Action

CommonlyAssociatedMotor program

GoalRepresentation

ExtractedGoals

Structures of Models

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Perceived Action

MotorCommands

SupramodalRepresentation

Perceived Action

CommonlyAssociatedMotor program

GoalRepresentation

AIM

GOADI

Perceived Action

Performance ofAction

ASL

3. Associative Sequence Learning Vertical associations Indirect vertical associations

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3. Associative Sequence Learning Vertical Associations

A few may be innate The majority are formed in a Hebbian fashion.

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3. Associative Sequence Learning Indirect vertical association

Word

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smile

smile

3. Associative Sequence Learning Indirect vertical association

Word

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3. Associative Sequence Learning Correspondence problem (imitation)

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Observer Model

Visual Input

3. Associative Sequence Learning Correspondence problem

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Observer Model

Visual Input

3. Associative Sequence Learning Correspondence problem

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Observer Model

Visual Input

3. Associative Sequence Learning Correspondence problem

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Observer Model

Visual Input

3. Associative Sequence Learning Correspondence problem

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Observer Model

Visual Input

smile

3. Associative Sequence Learning Correspondence problem

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Observer Model

Visual Input

smile

Summary• Correspondence problem

• Active Intermodal Mapping (AIM)

• Goal-Directed Imitation (GOADI)

• Associative Sequence Learning (ASL)

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Contents Introduction

The Correspondence Problem

Three theories Active Intermodal Mapping (AIM) Goal-Directed Imitation (GOADI) Associative Sequence Learning (ASL)

Contrasting 3 theories Issue 1: Effect-dependency Issue 2: Awareness

Questions for ASL model: about Intention

Conclusion & Discussion

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Contrasting 3 theories★ two criteria

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Effector-dependency Awareness

Whether observation can support effector-dependent learning

Whether Imitation Learning can occur without awareness

Effector-dependency issue

• Some kinds of Training are not generalized to others.

ex) Right-Left hand using is not convertible (Bapi et al, 2000)

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Explanation for Effector-dependency

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Different predictions of 3 Theories on Effector-dependent observational learning

 AIM GOADI ASL

Frequency None (always effector-independent)

Rare (Actions not encoded at global level)

Usual

Principal (transformed into) Supramodal representation

action “Effects" Visual experience paring with motor activation

Result various motor outputs

Goal-directed action ex) finger movement

Experiment: Effector-dependent learning by observation.

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(Bird and Heyes, 2005; Heyes and Foster, 2002; Osman etal., 2005)

Direct link between Perception & Action

- Observers’ better performing(:typing speed) the finger movement sequence with using same finger of model’s

Explanation for Awareness

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  AIM GOADI ASLAwareness O O X / ?

Mechanism Active Goal-directed Automatic

Base not mentione

d

Goal-directed imitation’

theory

(on next slides)

Experimental Evidences for automatic imitation

1. Electrophysiological(MEP) study: Motor facilitation by action observation (Aziz-Zadeh et al., 2002; Maeda et al., 2002; Strafella and Paus,2000)

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2. ‘Chameleon effect’ in social interaction(Chartrand and Bargh, 1999; Lakin and

Chartrand, 2003)

Questions for ASL model

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• Intentional vs. incidental imitation

ASL Model is NOT considering - a representation of the model’s action goals, - role of amodal (non-sensory, non-motor)

representations of action.

Contrary to our introspective plausibility

Thoughts about the Intentionality issue

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Relationship between intentional processing and the vertical associations mediating imitation

Without Intention,Movement observation Motor activation by ASL. Automatic process (e.g.: Hebbian learning.)normally INHIBITED to prevent overt imitation

With Intention,Disinhibition on vertical associationFormulation of verbal description of observed action.c.f) Vocabulary limitation : dancers and gymnasts’ special vocab uses.

Conclusion(part 2.)

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model’s Goals explaining what is imitated,

Vertical Association explaining How imitation is achieved.

한 가지 모델만으로 모방 학습에 대해 설명할 필요는 없음 .

모방 학습 상황에 대한 이론으로서 , GOADI 와 ASL 이 상호보충적 설명 가능 .

Discussion#1. Is ‘Imitation’ Default of Human cognitive-behavior system? How broadly can it be applied over areas? (Social/ Functional / Evolutionary..)

#2.In the Goal-Directed ImitationThe goal of the imitator is to produce exactly the same body movement.Cases like this pose the correspondence problem, and yet GOADI is silent about how this problem may be solved.

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