Slow progress in the 1970’
’s
1970
1970’s
Biological Foundations
Foundations of the
Reactive P
aradigm
aradigm
Reactive
Paradigm
Ch 3
E.g: Slow robots…
Stanford Cart (1977)
Stereo vision and an internal
map of the world. Average
speed: 1 meter / 10 minutes
1+1 ?
Thomas Hellströ
Hellström
Hellström
Umeå
Umeå University
Sweden
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Why explore b
iology?
ology?
biology?
Why not explore b
iology?
ology?
biology?
V Animals and humans provide existence
proofs of different aspects of intelligence
”Airplanes don’t flap their wings!”
V Many ”simple” animals such as insects, fish and
frogs exhibit intelligent behaviors with
virtually no brain
No, but almost everything else about
a plane’s aerodynamics imitates a
V Animal studies can yield computational
models
bird’s flight.
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The o
rigin of Behaviors
Behaviors
origin
New sources for info
ormation
inf
information
Innate - born with a behavior
Part of a sequence of innate behaviors
3. Innate with memory
4. Learned
1.
V Ethology
2.
Study of animal behavior
V Cognitive psychology
Study of how humans think and
represent knowledge
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Example:
Part of a Sequence of Innate Behaviors
Example:
Example: Innate behavior
™ Arctic terns live in Arctic
(black, white, gray environment, some grass)
but adults have a red spot on beak
Mating Cycle of Digger Wasp
– Female mates with male
– Female builds nest
– Female lays eggs
Logical sequence but consider
– The wasp doesn’t need to
“know” the sequence
– Each step in the sequence is
“triggered”
™ When hungry, baby pecks at parent’s
beak, who regurgitates food for baby to eat
™ How does it know its parent?
It doesn’t, it just goes for the largest red
spot in its field of view
- Only red thing should be an adult tern
- Closer = large red
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Example: Learned behaviors
Example: Innate with Memory
Baby Lions
– Baby lion must be taught to hunt!
Baby Bees
– Baby bees buzz around the hive in a pattern
– Believed to be learning the opening of the hive
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Behavior Defin
nition
Defi
Definition
((template)
template)
template)
””The
The Feeding Behavior
RED
PECK AT RED
FEEDING BEHAVIOR
Sensory
Input
© Thomas Hellström 2006
BEHAVIOR
Pattern
of Motor
Actions
Sensory
Input
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Pattern
of Motor
Actions
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T
he Releaser Template
The
Sensory input and/or
Innate releasi
eleasing Mechanisms
Mechanisms
Nobel prize in medicine 1973
- von Frisch
- Lorenz
- Tinbergen
Releaser
internal state
present? N
Y
…
"for their discoveries concerning
organization and elicitation of individual and
social behaviour patterns"
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T
he Feeding Releaser
The
Innate rreleasing
eleasi
eleasing Mechanisms
Mechanisms
Sensory input and/or
RED and Hungry
Releaser
Releaser
Sensory input and/or
internal state
internal state
present? N
Y
present? N
Y
…
…
RED
BEHAVIOR
Sensory
Input
© Thomas Hellström 2006
PECK AT RED
FEEDING BEHAVIOR
Pattern
of Motor
Actions
Pattern
of Motor
Actions
Sensory
Input
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Example:
ock
Example: C
ockroa
roach hide
Cockroach
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Implicit chaining
• light goes on, the cockroach turns and runs
• when it gets to a wall, it follows it
- The behaviors are activated in a
sequence controlled by their Releasers
• when it finds a hiding
place (thigmotrophic),
goes in and faces
outward
- Not explicit, but through external and
internal signals
• waits until not scared,
then comes out, even
if the lights are turned
back off earlier
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Example:
ock
Example: C
ockroa
roach hide
Cockroach
Example:
ochroa
Example: C
ochroach hide
Cochroach
1. light goes on, the cockroach turns and runs S→R
Taxis
.
2. when it gets to a wall, it follows it S→R
3.
4.
Programmed in C++, << 100 LOC. Shows :
– taxis (oriented relative to light, wall, niche)
– fixed action pattern (persisted after light was off)
when it finds a hiding
place (thigmotrophic), Taxis
goes in and faces
outward
waits until not scared,
then comes out, even Fixed-action
if the lights are turned patterns
back off earlier
– reflexive
(stimulus, response)
– implicit sequencing
(conscious?)
– use of internal state
Sequencing (Conscious)
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LIGHT
Find Releasers
present?
Break into Behaviors
N
Y
Flee
SCARED
light goes on, the cockroach
turns and runs
light goes on, the cockroach
turns and runs
Flee
IR LIGHT
Internal state !
present?
Y
N
Followwall
SCARED & SURROUNDED
present?
Y
N
Hide
when it gets to a wall, it
follows it
Followwall
when it gets to a wall, it
follows it
when it finds a hiding place
(thigmotrophic), goes in and
faces outward
when it finds a hiding place
(thigmotrophic), goes in and
faces outward.
waits until not scared, then
comes out
Hide
waits until not scared, then
comes out
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LIGHT
Sequencing (chaining)
chaining)
sensor
present?
Wheel
encoders
• Implicit and driven by perception and
Y
N
Flee
Action and Sensing
turn 180 deg.
Speed(10)
SCARED=TRUE
light goes on, the cockroach
turns and runs
IR LIGHT
internal states
present?
Y
• Simple behaviors operating
independently can lead to what an
outside observer would view as a
complex sequence of actions
N
Followwall
IR
steer =F(dist to wall)
Speed(10)
IR
SCARED & SURROUNDED
present?
Y
Wheel
encoders
Hide
N
turn 180 deg.
Speed(0)
stop
when it gets to a wall, it
follows it
when it finds a hiding place
(thigmotrophic), goes in and
faces outward.
waits until not scared, then
comes out
IR
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Conc
Concurre
urrent behaviors
behaviors
Innate releasi
eleasing Mechanisms
Mechanisms
Behaviors often execute concurrently
and independently
• Analogy:
IRMs work on THREADS,
not sequential processing!
• Very simple modules
• Modular building blocks since not directly
linked
• If one module (part of brain) fails, what
happens?
• Equilibrium
- Feeding squirrels
feed or flee? : hesitate in between
• Dominance
- Sleepy and hungry! : either sleep or eat
• Cancellation
-Sticklebacks (fish) with overlapping territories.
defend or attack? : build a new nest !
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Homing Piegon’
Piegon’s Orientation
Pigeons can navigate hundreds
of km to a goal, even with no
visual cues to the path home.
Appears that they have multiple
cues
Perception
Cognitive psychologist:
J.J Gibson
Ulrich Neisser
• If sunny day, pigeons seem to
use biological clocks and sun
angle.
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Two functions of perception
How do we know that?
•When birds have clocks shifted by 6
hours (using artificial lighting), direction
is off by 90 deg.
• When sky is overcast (sun not visible),
clock-shifted birds head off in correct
direction. Appear to be using another
mechanism independent of sun and time
of day.
• When birds are wearing magnets, they
are confused on overcast days, but not
on sunny days.
– Release: To release a behavior
– Guide: To provide information needed to
accomplish a behavior
• Action-oriented perception:
– Perception filters the incoming sensory
stream to extract information specific to
the task at hand
– Note: difference from hierarchical worldmodel building
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Neisser:
Neisser:
Two kinds of Perception
Perception in the Brain
Gibson’
Gibson’s Ecological Approach
•
• Direct perception (affordances):
•
– Doesn’t require memory, inference, or interpretation
– Minimal computation
– Rapid execution time
– Example: Optic flow
•
• Recognition:
– Connects with problem solving and other cognitive
activities
– Deals with more “top-down”, “model based”
perception
– Example: find your car in the parking lot
•
Acting and sensing co-evolved as agents
survived in a particular environment.
The environment affords the agent what it
needs to survive.
The perception needed to release or guide
the “right action” is directly in the
environment, not inferred or memorized
Ex. Red on Artic Terns== food
Ex. Sound of filling container==full
These percepts are called affordances or said
to be obtained through direct perception:
“perceivable potentialities of the environment
for an action”
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Behaviors as Schemas
Schemas
Schema Theory
™ Parameterized like a class in OOP
™ Creation of a specific schema:
™ Inspired by psychology
(used there since the early 1900’s)
Schema Instantiation (SI)
™ Applied to robotics by Arbib
™ Generic template for doing an activity
™ Contains:
– Knowledge of how to act and/or perceive
– Data structures (not in pure reflexive behaviors)
– Models
– Algorithms
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Perceptual Schemas
Sensing and Perception in Robotics
™ The inputs (percepts) to the Motor Schemas
™ The Perceptual Schema pre processes inputs to suit the
Motor Schemas
™ Perceptual Schemas are recursively defined. I.e.: they
can serve as input to other Perceptual Schemas.
PSS1
Camera
PSS2
PS1
The Perceptual Schema produces a Percept
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Infrared sensor
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Dinner time:
Ex. Fly Snapping Behavior IRM
Releaser:
small moving dark blob
Perceptual
schema
Motor
schema
present? N
Y
eye
snap,
100%
x,y,z,
100%
track
snap
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2 flies at the same time
Confused frog:
frog:
Releaser:
small moving dark blob
present?
Y
Left eye
track
N
snap,
100%
x,y,z,
100%
snap
Snap at
vector sum
(middle)
Releaser:
small moving dark blob
present?
Y
Right eye
track
x,y,z,
100%
N
snap,
100%
snap
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Schemas
Conclusions for Behaviors
™ All animals possess a set of parallell and
™ Can operate asynchronously and wait for the
distributed behaviors
percepts
™ No predefined hierarchy between different
schemas exists
™ Schemas can be instantiated and
deinstantiated at any time
™ Outputs vectors: direction and strength
™ Releasers rely on both internal state and
external stimulus
™ Perception is filtered; perceive what is relevant
to the task (action-oriented perc.)
™ Some behaviors and associated perception do
not require explicit knowledge representation
(e.g., rely on affordances)
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Ideas bubbling up for robotics (Murphy)
– Maybe programming in terms of behaviors is
better than STRIPS or trying to set up a
complex hierarchy
– Intelligence has something to do with
agent’s ecological niche: its abilities, its tasks
(survival), and environment
– Perception is going to be critical because it
releases and guides actions
– IRMs, Schemas are nice ways to start
thinking about the computational structure
of programming a robot
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