Psychology 452 Week 9: The Synthetic Approach

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Psychology 452 Week 9: The Synthetic Approach Analytic approach to psychology The synthetic alternative Grey Walter s Turtles Braitenberg s Vehicles A toy example Grey Walter s Turtles William Grey

They were recently rediscovered and recreated in Bristol His work is described in the 1953 book The Living Brain Recording Complex Behavior Elsie s Behavior: Getting Around?

1 Psychology 452 Week 9: The Synthetic Approach Analytic approach to psychology The synthetic alternative Grey Walter s Turtles Braitenberg s Vehicles A toy example Grey Walter s Turtles William Grey Walter built precursors of Braitenberg s vehicles in 1948 and They were recently rediscovered and recreated in Bristol His work is described in the 1953 book The Living Brain Recording Complex Behavior Elsie s Behavior: Getting Around? Candles were fixed to the turtles shells, and long exposure photographs were taken as the machines moved Traces of light in the photographs recorded the paths of the machines Approaching light, and then circling it at a distance Elsie Returns Home Attracted by the light, Elsie returns to her hutch to recharge her power supply Elsie s Complex Behaviour A screen hides the light, it can t be seen Elsie oscillates, but then hits and moves the screen When the light appears, she circles it at a distance

Elsie s Behaviour: Choice Elsie s Behaviour: Self-Aware?

choosing it beyond the second one The robot lingers before a mirror, flickering, twittering and jigging like a clumsy

The behaviour of a creature thus engaged with its own reflection is quite specific, and on a purely empirical basis, if it

Elsie s Social Behaviour How Should We Do Psychology?

Psychological phenomena are complicated How can psychology be understood?

2 Elsie s Behaviour: Choice Elsie s Behaviour: Self-Aware? Elsie chooses between alternatives She circles the first light When the second light is seen, she moves and circles it, choosing it beyond the second one The robot lingers before a mirror, flickering, twittering and jigging like a clumsy Narcissus. The behaviour of a creature thus engaged with its own reflection is quite specific, and on a purely empirical basis, if it were observed in an animal, might be accepted as evidence of some degree of self-awareness How can this behavior be explained? Elsie s Social Behaviour How Should We Do Psychology? Elsie dances with Elmer, and vice versa, because of the candle The two then race to the hutch, with Elsie winning Psychological phenomena are complicated How can psychology be understood? Perhaps psychology is like physics Carve phenomena into categories Look for laws operating within categories Is that how we approached Elsie? Sir Roger Penrose Example 1: Intelligence Example 2: Functional Analysis Battery of tests Factor analysis of test scores Labeling of factors Intelligence analyzed into a set of mostly orthogonal abilities (e.g., Gardner s multiple intelligences) Linguistic Logical-mathematical Bodily-kinaesthetic Spatial Musical Interpersonal Intrapersonal Naturalist Howard Gardner Define a function of interest Measure the function Decompose the function into an organized set of subfunctions on the basis of experimental results Repeat this process on subfunctions that have been identified

Example 3: Double Dissociations Example 4: Neuroimaging Find a brain lesion that affects one behaviour, but not another Find a different brain lesion that has the reverse effect on the behaviours

neural mechanisms A modern variant on lesioning Psychology Is Hard To Do A Synthetic Alternative?

3 Example 3: Double Dissociations Example 4: Neuroimaging Find a brain lesion that affects one behaviour, but not another Find a different brain lesion that has the reverse effect on the behaviours Explain the phenomenon by appealing to differently located neural mechanisms Give different tasks while scanning Look for different brain areas lighting up Explain tasks as a function of different neural mechanisms A modern variant on lesioning Psychology Is Hard To Do A Synthetic Alternative? The operations of our minds do not depend on few and simple laws because our brains have accumulated many different mechanisms over aeons of evolution. This means that psychology can never be as simple as physics, and any simple theory of mind would be bound to miss most of the big picture. The science of psychology will be handicapped until we develop an overview with room for a great many smaller theories (Minsky, 1985, p. 322). Only about 1 in 20 [students] gets it -- that is, the idea of thinking about psychological problems by inventing mechanisms for them and then trying to see what they can and cannot do (Minsky, 1995, personal communication). Grey Walter s Vehicles: The Basics Synthetic Implications Two radio tubes Two sensors (light and touch) Photocell is linked to steering mechanism No light -- continuous forward exploration combined with oscillation Weak light -- steering inhibited, and machine moves forward towards the light Strong light -- dazzled state, steering kicks back in at double speed Touch sensor activates more random oscillation to permit obstacle avoidance The behavior of the turtles is very complex But it is known to emerge from simple principles, modulated to a certain degree by a complicated environment Does Grey Walter have a better understanding of such behaviors than an observer of the machines?

4 Synthetic Psychology Getting Around Propose an architecture Play with your proposed architecture What can you build with it? What can t you build with it? Example: The thought experiments proposed by Braitenberg in his book Vehicles. Propulsion proportional to sensation E.g., motor speed related to temperature "Imagine, now, what you would think if you saw such a vehicle swimming around in a pond. It is restless, you would say, and does not like warm water. But it is quite stupid, since it is not able to turn back to the nice cold sport it overshot in its restless ness. Anyway, you would say, it is ALIVE, since you have never seen a particle of dead matter move around quite like that." What will produce complex behavior in this vehicle? Fear And Aggression Cross connections and inhibitory links provide more complicated behaviors Multimodal Sensors & Effectors "This is now a vehicle with really interesting behavior. It dislikes high temperature, turns away from hot places, and at the same time seems to dislike light bulbs with even greater passion, since it turns toward them and destroys them. On the other had it definitely seems to prefer a well-oxygenated environment and one containing many organic molecules, since it spends much of its time in such places. But it is in the habit of moving elsewhere when he supply of either organic matter or (especially) oxygen is low." Braitenberg describes this machine as having VALUES and KNOWLEDGE. Spatial Sensors Foresight "You will get a picture. It will not be scrambled information about the outside world; it will be a representation of the order of things, of their neighborhood relations and, roughly, of the distances between them." In other words, the responses of adjacent sensors now becomes important because of their adjacency. Expectations are extremely important for the survival of an organism. "All that we need is a mechanism to predict future events fast enough so that they will be known before they actually happen." A recurrent connectionist network?

5 Uphill Analysis Downhill Synthesis The complexity of the vehicles behaviors leads to complex attributions These attributions overestimate the underlying simplicity of the systems Viewed as a geometric figure, the ant s path is irregular, complex, hard to describe. But its complexity is really a complexity in the surface of the beach, not a complexity in the ant (Simon, 1996, p. 51) "It is pleasurable and easy to create little machines that do certain tricks. It is also quite easy to observe the full repertoire of behavior of these machines -- even it it goes beyond what we had originally planned, as it often does. But it is much more difficult to start from the outside and try to guess internal structure just form the observation of the data. [...] Analysis is more difficult than invention in the sense in which, generally, induction takes more time to perform than deduction: in induction one has to search for the way, whereas in deduction one follows a straightforward path. A psychological consequence of this is the following: when we analyze a mechanisms, we tend to overestimate its complexity." A Synthetic Hypothesis Example: Thoughtless Walker An ant, viewed as a behaving system, is quite simple. The apparent complexity of its behavior over time is largely the reflection of the environment in which it finds itself (Simon, 1996, p. 52) What are the implications of this view for psychology? What are the implications of this view for simulation methodologies? What are the pros and cons of connectionism in the context of this hypothesis? I ve used an effective classroom activity to introduce students to the synthetic approach Their task is to take K NEX parts, and used them to build a system that walks Axle Considerations Two-Legged Module Students have to discover how to convert an axle s rotation into a stepping motion Students have to develop a structure that can stand and balance Students usually develop a modular system that looks like the system on the right The next step in the synthetic approach is to watch it behave, and look for emergent behaviours

6 Emergence 1 Emergence 2 The first surprise that students have is that the behaviour of the machine is realistic, but the two-legged module does not walk The second surprise that students have is that a four-legged system walks, but only when its motors run in opposite directions MPEG Video MPEG Video Emergence 3 The third surprise that students have comes from the conditions under which a sixlegged system walks MPEG Video The walking of these systems can be described as thoughtless information processing that results in a lowenergy coordination of stepping motions Analysis The Allure Of Emergence Against Representation Behaviour-based roboticists reacted against the analytic traditions of symbolic AI The realization was that the so-called central systems of intelligence or core AI as it has been referred to more recently was perhaps an unnecessary illusion, and that all the power of intelligence arose from the coupling of perception and actuation systems (Brooks, 1999) Rodney Brooks Behaviour-based robotics is a strong reaction against symbolic models In particular I have advocated situatedness, embodiment, and highly reactive architectures with no reasoning systems, no manipulable representations, no symbols, and totally decentralized computation (Brooks, 1999)

7 Psychology Needs Representation Limitations Of Embodiment Cognitive psychology appeals to representation Representation is required for higherorder processing Because explanations attempt to capture generalizations, and different vocabularies reveal different generalizations, we find ourselves forced to resort to what I call a cognitive vocabulary in revealing certain fundamental patterns of intelligent, largely rational behavior (Pylyshyn, 1984, p. 2). Zenon Pylyshyn Even roboticists are wary of abandoning representation It had to be admitted that behavior-based robots did not accomplish complex goals any more reliably than machines with more integrated controllers. Real insects illustrate the problem. (Moravec, 1999) Hans Moravec Is Synthetic Psychology Possible? There is nothing in the synthetic approach per se that prevents one from constructing systems that use representations. Describing a model as being synthetic or analytic is using a dimension that it is completely orthogonal to the one used when describing a model as being representational or not. (Dawson, 2003) Representational Not Representational Analytic Production Systems (Newell & Simon) Mathematical Models (Rescorla-Wagner) Synthetic PDP Networks (My own lab) Behaviour-Based Robotics (Brooks)

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