Modeling and Imagery: Intro

Wilson & Knoblich, 2005

Conspecifics? The case for motor involvement in

perceiving conspecifics•The idea that we use a part of motor cortex

to interpret the movements of others of our species

Starts with the notion that other people are special (perceptually), because they can be directly compared with ourselves (& they’re the only thing that can be)

Perceiving people Generates motor representation

•But no movement•So why have a movement plan without

movement? Purpose?

•It’s proposed here it’s for an emulator•This is something that in computer

hardware/software terms enables programs intended for one device to run on others

•Perhaps the motor plan enables us to predict other’s actions

Covert imitation of actions Chameleon effect

•Facial expression (cinema, the nodder)•Gestures & body sway (mothers/babies,

launderette, bar)•Tone of voice, pronunciation (Janet &

Corinne)•Ever watched a sport you play and

experienced that you are “playing” yourself?

Covert imitation of actions Automaticity of imitation

•Stimulus-response compatibility•Responses fastest when cue matches

response•Suggests motor programs for response are

best cued by watching the same or similar action•Which in turn suggests imitation is automatic

Covert imitation of actions Neonate imitation

•One-month olds•Mouth opening, tongue protrusion, facial

expression of emotion, blinking, vowel sounds, /m/ sound…

•“Slightly older”•Tongue protrusion to side, more consonants

Covert imitation of actions Frontal lobe damage

Loss of inhibition Automatic tendency to imitate

•(evidence for covert but inhibited imitation in the rest of us)

Covert imitation of actions Mirror Neurons

•Previous examples: overt imitation

•This example: covert imitation exists when overt behavior is absent

•These neurons (in premotor cortex of monkey) fire both when acting and when watching actionDiagram shows activity in both

premotor and parietal areas

Covert imitation of actions Mirror Neurons

•Previous examples: overt imitation•This example: covert imitation exists when

overt behavior is absent•These neurons (in premotor cortex of monkey)

fire both when acting and when watching action•Note: this is in monkeys, not humans, but the

idea is that perhaps we also have imitative circuitry in our brains

Covert imitation of actions Activation of motor

planning areas in humans• Observation of other’s body

movement (finger, hand, arm, mouth, foot) leads to activation of motor cortex•Only occurs for plausible

movements•Also occurs for complex

movements…more so for those who are expert in the activities

•Heard sounds promote activation of hand parts of motor cortex

Covert imitation of actions Activation of motor planning

areas in humans• Observation of other’s body

movement (finger, hand, arm, mouth, foot) leads to activation of motor cortex• Implies new mappings can be

learned•Mappings can be from

different stimuli (don’t have to be matched, e.g. hand for hand)

•Thus music can be “heard” as movement, provided you are familiar with the required movement

Covert imitation of actions Facilitated muscle activity

•Trace EMG activity found in response to watching same limbs of others move

Motor related brain rhythms•Rhythms blocked by motor activity are

also blocked by observation•Suggests equivalence of perceived and

performed action

Why do we covertly imitate? Might be due to the need for action

understanding…•To assist in categorizing the action•To uncover the purpose behind the behavior•To understand the antecedents of the action

(why do this? Affective state)•Makes sense if both sensory and motor

consequences are initiated Might be something to do with language

evolution•Area F5 & Broca’s area

Why do we covertly imitate? …or we might be trying to perceive what

we are seeing•Serves as an “emulator”

•Can perhaps be used to fill in missing or scratchy information

•Can perhaps be used to project likely movements of other’s body even when unsighted

•Info must permeate other systems beyond the motor system for this to work

p. 464

Why do we covertly imitate? Contrasts w/other (previous) proposals

•Others “postdictive”, this is predictive This requires allocentric representation

of body•Can map something watched in 3rd person as

experienced in 1st person•Clear tie ins for modeling, no?

p. 464

Perception is predictive Your favorite CD/playlist Similar prediction has been shown in

movement perception•“Representational momentum”

•Forward shift accepted, backward rejected (explain) – p. 465 has further examples

•Suggests perceptual extrapolation•“Filling in” – the x-y example•Also found for human movement (point

light)

Perceptual Prediction & Emulation How does it work?

•Internal model – forward model (Jordan)•Avoids dependence on feedback (important

when considering chronometry) in ballistic movements

Perceptual Prediction & Emulation How does it work?

•Emulators (again)•See definition on p. 466•Model of external system run internally, in real

time• Implies information about external world can be

had before it occurs•Emulation easier for simple patterns, or for very

familiar patterns•Supported by the idea that when outcomes are

unpredictable, representational momentum is absent (rock bouncing down hill)

Motor involvement in perceptual prediction There must be a match between what

is seen and what is experienced (what is experienced is what builds the emulator)•In the case of watching human bodies, the

match is pretty good – we have one, so we “know” how it behaves

Does covert imitation get used for perceptual prediction in human movement?

Motor involvement in perceptual prediction Motor activation that precedes the

related perceptual event•Pianists generate motor imagery prior to

the event that relates to it•Motor activation of a finger used to play a

note occurs prior to the note being heard in a familiar piece of music

Motor involvement in perceptual prediction Predictive capabilities of mirror

neurons•Mirror neurons that fire to a hand grasp

of an object also fire when the hand is seen about to grasp when going behind a screen…but only if it is known there is an object behind the screen

Motor involvement in perceptual prediction Influence of motor learning on

perception•When a particular movement pattern is

learned, subsequent recognition of similar movement patterns improves

Motor involvement in perceptual prediction Superior perceptual prediction by

viewing oneself•Idea here is that if the internal model is

based on an estimation of the external reality, then it should be best when the external reality is one’s own!•And it is borne out•People watching themselves perform better

in point light task identification then those watching others

Motor involvement in perceptual prediction Superior visual judgment for

possible movements•Perceptual prediction is influence by

motoric knowledge

So, um, what? Internal emulators imply perceptual

sophistication of unparalleled complexity

That these are unconscious implies there is a lot going on of which we are not aware

That the events invoke motor imagery is really important…see next week’s audio slides