3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations1 Biological Foundations of the Reactive Paradigm Review Why? -comp. theory IRM Perception -Summary Describe the three levels in a Computational Theory. Explain in one or two sentences each of the following terms: reflexes, taxes, fixed-action patterns, schema, affordance. Be able to write pseudo-code of an animal’s behaviors in terms of innate releasing mechanisms, identifying the releasers for the behavior. Given a description of an animal's sensing abilities, its task, and environment, identify an affordance for each behavior. Given a description of an animal's sensing abilities, its task, and environment, define a set of behaviors using schema theory to accomplish the task.

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations2 Robots In the Hierarchical Paradigm

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations3 Timeline of Influences Braitenberg’s Vehicles Arbib’s Schemas Tinbergen & Lorenz & von Frisch Marr’s Computational Theory J.J. Gibson Neisser Middlestat Arkin’s Schemas Brook’s Insects Payton

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations4 Marr’s Computational Theory Level 1: What is the phenomena we’re trying to represent? for (i=nCol.. Level 2: How it be represented as a process with inputs/outputs? Level 3: How is it implemented?

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations5 Level 1: Existence Proof Level 1: What is the phenomena we’re trying to represent? Goal: how to make line drawings of objects? people can do this by age 10, computers should

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations6 Level 2: Inputs, Outputs, Transforms for (i=nCol.. Level 2: How it be represented as a process with inputs/outputs? light drawing retina (gradient) light lines (edges)drawing

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations7 Level 3: Implementation Level 3: How is it implemented? Center Surround Cell in retinal ganglion Sobel Edge Detector in computer vision

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations8 Class Discussion Give three examples of how biology has informed modern technology? –ex. Wright Brothers- control flaps on airplane wings

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations9 Behavior Definition (graphical) BEHAVIOR Sensory Input Pattern of Motor Actions

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations10 Types of Behaviors Reflexive –stimulus-response, often abbreviated S-R Reactive –learned or “muscle memory” Conscious –deliberately stringing together WARNING Overloaded terms: Roboticists often use “reactive behavior” to mean purely reflexive, And refer to reactive behaviors as “skills” WARNING Overloaded terms: Roboticists often use “reactive behavior” to mean purely reflexive, And refer to reactive behaviors as “skills”

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations11 Ethology: Coordination and Control of Behaviors Nobel 1973 in physiology or medicine von Frisch Lorenz Tinbergen INNATE RELEASING MECHANISMS

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations12 Arctic Terns Arctic terns live in Arctic (black, white, gray environment, some grass) but adults have a red spot on beak 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 (e.g., ethology grad student with construction paper) –Only red thing should be an adult tern –Closer = large red

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations13 behavior template BEHAVIOR Sensory Input Pattern of Motor Actions

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations14 “the feeding behavior” Feeding BEHAVIOR Sensory Input Pattern of Motor Actions REDPECK AT RED

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations15 the releaser template Releaser present? N Y /dev/null Sensory input and/or internal state

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations16 “the feeding releaser” Feeding BEHAVIOR REDPECK AT RED Releaser present? N Y /dev/null internal state RED & HUNGRY sensory input

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations17 Innate Releasing Mechanisms BEHAVIOR Sensory Input Pattern of Motor Actions Releaser present? N Y /dev/null Sensory input and/or internal state

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations18 Example: Hide Behavior Programmed in C++, << 100 LOC shows –taxis (oriented relative to light, wall, niche) –fixed action pattern (persisted after light was off) –reflexive (stimulus, response) –impliciting sequencing –use of internal state

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations19 Example: Cockroach Hide light goes on, the cockroach turns and runs 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 even if the lights are turned back off earlier

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations20 Reflexive Behaviors S-R light goes on, the cockroach turns and runs 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 even if the lights are turned back off earlier

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations21 Fixed Pattern Actions light goes on, the cockroach turns and runs 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 even if the lights are turned back off earlier

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations22 Exhibits Taxis light goes on, the cockroach turns and runs 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 even if the lights are turned back off earlier to light to wall to niche

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations23 Class Exercise Draw flowchart of how this works light goes on, the cockroach turns and runs 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 even if the lights are turned back off earlier light goes on, the cockroach turns and runs 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 even if the lights are turned back off earlier

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations24 Break into Behaviors light goes on, the cockroach turns and runs 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 Flee Follow- wall hide

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations25 Find Releasers light goes on, the cockroach turns and runs 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 Flee Follow- wall hide LIGHT present? N Y SCARED & SURROUNDED present? N LIGHT present? N Ooops, need internal state: Scared Ooops, need internal state: Scared

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations26 Internal State Set light goes on, the cockroach turns and runs 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 Flee Follow- wall hide LIGHT present? N Y SCARED & SURROUNDED present? N BLOCKED & SCARED present? N SCARED

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations27 Action light goes on, the cockroach turns and runs 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 Flee Follow- wall hide LIGHT present? N Y SCARED & SURROUNDED present? N BLOCKED & SCARED present? N SCARED steer 360, drive forward steer =F(dist to wall) drive forward const. steer =F(dist to wall) drive forward const. stop

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations28 Sensory Input light goes on, the cockroach turns and runs 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 Flee Follow- wall hide LIGHT present? N Y SCARED & SURROUNDED present? N BLOCKED & SCARED present? N SCARED steer 360, drive forward steer =F(dist to wall) drive forward const. steer =F(dist to wall) drive forward const. stop encoders IR

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations29 How Do You Link Them? light goes on, the cockroach turns and runs 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 Flee Follow- wall hide LIGHT present? N Y SCARED & SURROUNDED present? N BLOCKED & SCARED present? N SCARED steer 360, drive forward steer =F(dist to wall) drive forward const. steer =F(dist to wall) drive forward const. stop encoders IR

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations30 Analogy: IRMs work on THREADS, not sequential processing! Very simple modules Nice building blocks since not directly linked If one module (part of brain) fails, what happens?

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations31 What happens when there’s a conflict from concurrent behaviors? Equilbrium –Feeding squirrels-feed, flee: hesitate in-between Dominance –Sleepy, hungry: either sleep or eat Cancellation –Sticklebacks defend, attack: build a nest ?

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations32 Perception Two uses of perception (can be the same percept) –Release a behavior –Guide a behavior Action-oriented perception (Neisser) –Planning is not needed to act –Perception is selective Cognitive Activity World Perception of Environment Samples, Finds Potential Actions Acts & Modifies World Directs what to look for

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations33 Gibson’s Ecological Approach Acting and sensing co-evolved as agent 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 Percepts are called affordances or said to be obtained through direct perception

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations34 Gibsonian Affordances How do you know you’re going fast in a car? Or in a space movie? How do animals know when to mate? How do mosquitoes know to bite in the most tender areas? What should you do when you think you’re being stalked by a mountain lion? What’s your favorite fishing lure?

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations35 Sittability

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations36 But does this really hold for everything? “my car” versus “your car”? –Difference is where I parked it (memory) Semantic meaning (cars aren’t generic like nuts to a squirrel) Neisser’s Two Systems –Direct Perception: older, behavioral –Recognition: evolved later, deliberative

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations37 Review Questions What are the levels of a computational theory? Existence proof, inputs-outputs-transformations, implementation What is a behavior? A behavior is a mapping of sensory inputs to a pattern of motor actions Is sequencing normally implicit or explicit in IRM? implicit What is an affordance? A potentiality in the environment for an action

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations38 Schema Theory schema- is used in cognitive science and ethology to refer to a particular organized way of perceiving cognitively and responding to a complex situation or set of stimuli is generic, equivalent to an object in OOP –schema specific knowledge (local data) –procedural knowledge (methods) schema instantation is specific to a situation, equivalent to an instance in OOP a behavior is a schema, consists of –perceptual schema –motor schema

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations39 Behavioral Schema Motor Schema (MS) Perceptual Schema (PS) percept, gain action, intensity alternative PS, MS sequencing logic for reactive skills (judgment value function) Reflexive behaviors usually just have “methods”, not data

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations40 Ex. Fly Snapping Behavior IRM snap(blob)track(blob) x,y,z, 100% snap, 100% Releaser: small moving dark blob present? N Y /dev/null

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations41 Schema Instantiation (SI) snap(blob)track(blob) x,y,z, 100% snap, 100% Releaser: small moving dark blob present? N Y /dev/null

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations42 Schema/Schema Instantiation behavior schema releaser present? N 1. snap(blob)track(blob) snap(blob) track(blob) Perceptual Schema Library Motor Schema Library 2. snap(blob)track(blob) x,y,z, 100% 3.

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations43 Advantages modular can assemble new behaviors from existing schemas –learning by experimentation can substitute alternatives –reroute nerves

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations44 Instantiation for each eye snap, 100% snap(blob)track(blob) x,y,z, 100% Releaser: small moving dark blob present? N Y /dev/null snap, 100% snap(blob)track(blob) x,y,z, 100% Releaser: small moving dark blob present? N Y /dev/null Left eye Right eye Snap at vector sum (middle)

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations45 Where’s the MS and PS? light goes on, the cockroach turns and runs 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 Flee Follow- wall hide LIGHT present? N Y SCARED & SURROUNDED present? N BLOCKED & SCARED present? N SCARED steer 180, drive forward steer =F(dist to wall) drive forward const. steer =F(dist to wall) drive forward const. stop encoders IR

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations46 General Principles All animals possess a set of behaviors Releasers for these behaviors rely on both internal state and external stimulus Perception is filtered; perceive what is relevant to the task Some behaviors and associated perception do not require explicit knowledge representation (e.g., rely on affordances)

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations47 Silicon v. Carbon Individual robots must survive, not species –detection of non-productive behaviors –graceful degradation Must be able to predict emergent behaviors Not clear how to learn quickly Robots need more alternative perceptual schemas since poorer understanding of the environment

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations48 Unresolved Issues How to resolve conflicts? –behavioral arbitration/combination When is explicit representations, memory needed? How to set up or learn new sequences of behaviors What are the affordances for a particular ecology?

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations49 Take Home Thoughts… Ideas bubbling up for robotics –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

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations50 Review Questions Think about the robots at the WTC. What are affordances of victims? color, motion, sound, heat Can schema theory represent behaviors in both biological and computational systems? yes A behavior schema is composed of at least the following: motor schema and a perceptual schema What is an example of behavior-specific knowledge? sequencing in a skill, alternative PS or MS

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations51 BEHAVIOR Sensory Input Pattern of Motor Actions Releaser present? N Y /dev/null

3 Introduction to AI Robotics (MIT Press)Chapter 3: Biological Foundations52 Inhibition while (TRUE) { predator = sensePredator(); //has a time delay if (predator==PRESENT) //as long as predator persists flee(); else { food = senseFood(); hungry = checkStateHunger();... } } Could also be done as an interrupt