1. 1 2 3 4 Modeling the development of mirror neurons Problem Solution
Giorgio Metta, Paul Fitzpatrick • MIT AI Lab, Humanoid Robotics Group •
Acknowledgments:
This work is funded by DARPA as part of the “Natural Tasking of Robots Based on Human Interaction Cues” project under contract number DABT C 4
Mimicry
The robot mimics the observed action trying to fulfill the goal rather than an actual movement
Question: How do mirror neurons develop?
Answer: Two stage hypothesis: learn about objects and then imitate the goal of an action if directed towards the same object.
Problem
Facts
F5 contains two classes of neurons: canonical and mirror. Both classes respond when object-directed actions are executed.
Canonical neurons respond to the presentation of an object according to the potential grasp types the object affords.
Mirror neurons respond to an observed action in accordance to the grasp type. 1 3
side tap
back slap
pull in
push away
A toy car: it rolls in the
direction of its principal axis
A bottle: it rolls orthogonal to the
A toy cube: it doesn’t roll,
it doesn’t have a principal axis
A ball: it rolls,
Motor vocabulary
identify
and
localize
object
search rotation
Previously-poked
prototypes
Learn the “geometry” of poking
E.g. poking from the left causes the object to move to the right
-200
-150
-100
-50 50
100
150
200
0.05
0.1
0.15
0.2
0.25
0.3
0.35
direction of movement [degrees]
P(x)
Exploiting affordances during poking
When a known object is presented to the robot, it chooses the appropriate action to make the object roll
Clustering
Interpreting observations
A foreign manipulator (human) pokes an object
The direction of movement is compared with the object afforadance 2
Final position
Initial position
Example 1
Example 2
Object, goal connects robot and human action
Our solution
We used poking and prodding as a precursor to full-blown manipulation
1. Learn about object affordances (canonical neurons)
2. Interpret observations on the basis of affordances (mirror)
3. Poke/push objects according to their affordances
4. Mimicry
Solution
Learn about object affordances
The affordance considered is the direction of movement with respect to the object’s principal axis 10 20 30 40 60 70 80 90
0.4
0.45
0.5
difference between angle of motion and principal axis of object [degrees]
estimated probability of occurrence
Rolls at right
angles to
principal axis
Bottle, “pointiness”=0.13
Motivation
Our inspiration comes from neuroscience: in particular, mirror neurons. This is a class of neurons found in the monkey's frontal cortex (area F5). A particular mirror neuron is activated both when the monkey executes an action and when it observes the same action performed by somebody else. Mirror neurons can be related to gesture recognition, language, and learning by imitation.