«by Sanjay Chandrasekharan B.Sc., M.C.J, M.A. A thesis submitted for examination to the Faculty of Graduate Studies and Research in partial ...»
Epistemic Structure: An Inquiry into How Agents
Change the World for Cognitive Congeniality
B.Sc., M.C.J, M.A.
A thesis submitted for examination
to the Faculty of Graduate Studies and Research
in partial fulfillment of the requirements for the degree of
Doctor of Philosophy
Institute of Cognitive Science,
March 24, 2005
© Sanjay Chandrasekharan
Carleton University Cognitive Science Technical Report 2005-02.
http://www.carleton.ca/iis/TechReports Dedication To my parents, Sari, and Devi Mookambika ii Abstract This thesis presents cognitive mechanisms that explain how humans and other organisms generate epistemic structures (ES) in the environment. Epistemic structures are structures generated systematically in the world by organisms to minimise cognitive load, for oneself, others, or both. Examples of ES in non-human organisms include pheromones, markers etc. For humans they include labels, colour codes etc.
Adding structures to the world for cognition is a fundamental adaptive strategy that exists across species. So a basic mechanism, growing in complexity, is required to explain how the strategy works in different species, from ants to humans. Such a mechanism is proposed, starting from low-level organisms and building up to humans. The model for lower organisms proposes that they learn the epistemic (i.e. knowledge) value of structures they inadvertently generate in the world (like pheromones). This learning of epistemic value is based on a feedback of cognitive load. Results from a proof-of-concept multi-agent simulation, based on the Q-learning algorithm, provide support for the model.
This model is then extended to the human case, using a set of theoretical arguments and examples, accounting for situations where humans generate ES for themselves and others. The case where structures are generated exclusively for others requires a more complex model. Based on further arguments and evidence, mental simulation of action is proposed as the mechanism underlying this case. This hypothesis is tested using a scenario-based methodology, adapted from counterfactual thinking research. Participants are asked to provide solutions to real-life problems involving a series of actors, including iii robots and dementia patients. Results indicate that simulation is the stronger candidate mechanism underlying ES generation just for others.
The final section examines the robustness of the epistemic structure strategy, using the passing problem in the robotic soccer simulation environment. The experiments show that adding ES to the world (yells) increases passing accuracy by 8-17 percentage points, compared to a centralised decision-making strategy. The ES strategy is also shown to perform better in high-noise and high-processing load situations, indicating that this robustness could act as a driving mechanism in the evolution of ES as a survival strategy.
Keywords: Epistemic Structure, Environment Structure, Distributed Cognition, Situated Cognition, Mental Simulation, Counterfactual Thinking, Animal Signaling, Cognitive Modeling, Cognitive Engineering, Teleological Functionalism.
AcknowledgementsI am indebted to my supervisors Babak Esfandiari and Robert West for helping me develop the ideas presented in this dissertation. Special credit goes to Babak for bringing me down to earth from my frequent flights of fancy, and insisting that experimental evidence is what counts. Besides strengthening the thesis, he has contributed greatly to my development as a researcher. A big thanks goes to Robert, for his ready support for my ideas and projects, patient help with statistics, strong and clear connections and pointers to related research, and above all, for taking the time and effort to guide me even as he was dealing with challenging times of his own.
This thesis would not have materialised without the support and direction of Dr. Andrew Brook. I would like to say a very special thanks to him, particularly for helping me put out the numerous fires I have taken to his door over the years. He also helped me develop my ideas, pointed out major flaws in argumentation, suggested solutions, and fine-tuned my writing.
I am grateful for the enthusiasm, critical observations and patience of the other members of my committee -- Dr. Marie-Odile Junker, Dr. Steve Marsh, and Dr. Chris Davis. I would like to specially mention Dr. Junker’s faith in my abilities, and her staunch moral and material support, particularly during some critical phases in the development of my ideas.
Credit also goes to Dr. Peter Todd and Dr. John Hutchinson of the ABC group for recognizing my ideas and providing focused feedback. I am also grateful to the ABC group for an intellectually stimulating year in the great city of Berlin.
It was a pleasure having Dr. David Kirsh as my external examiner, and I thank him for his enthusiasm and support for my project.
A big thanks goes to my absolutely wonderful colleague and collaborator Terry Stewart.
He patiently heard out my proposals, did some amazing coding in the span of few weeks to develop the simulation reported in chapter 4, and provided threads that helped in connecting my different projects together. He also helped me with code to analyse the Robocup data. Thanks a bunch, Terry!
Thanks also to my friend Ron Boring, for helping me with the early design of the psychology experiment, and pats on the back during some trying times. Kamilla Johannsdottir and Jennifer Schellinck have been wonderful friends as well, helping me with the ratings for the psychology experiment, commenting on the drafts of the thesis, and acting as sounding boards for my ideas. I am obliged to Neal Arthorne for developing the Robocup code and the log analysis tool. Tarek Hassan provided invaluable help in troubleshooting the Robocup code, and his enthusiasm for my proposals helped me get over some rough patches.
My wife Saritha organized participants’ schedules for the psychology experiment, assisted me with data entry, gave me the shelf-talker example, and helped me run the Robocup simulations. All the while running an efficient house, and bringing home the major chunk of the bacon. Thanks a lot for all that, Sari! But most of all, thanks for being there.
I am indebted to my parents, my sister and my brother-in-law, whose unquestioning support helped me join and stay in the Ph.D. program. Thanks also to the great country and tradition they are part of, which cherishes and nourishes the pursuit of knowledge, and subsidises higher learning. Looking at the changes taking place around me, I realize that many have unknowingly made sacrifices and tightened their belts for me to reach here. I am beholden to them.
Finally, a big thanks to Canada, Canadians, and the Malayali community in Ottawa for welcoming me, and making me feel at home.
~~~~~~~ When his father told him about his alarm at having forgotten even the most impressive happenings of his childhood, Aureliano explained his method to him, and José Arcadio Buendía put it into practice all through the house, and later on imposed it on the whole village.
With an inked brush he marked everything with its name:
table, chair, clock, door, wall, bed, pan.
He went to the corral and marked the animals and plants:
cow, goat, pig, hen, cassava, caladium, banana.
Little by little, studying the infinite possibilities of a loss of memory, he realized that the day might come when things would be recognized by their inscriptions but that no one would remember their use. Then he was more explicit.
The sign that he hung on the neck of the cow was an exemplary proof of the way in which the inhabitants of
Macondo were prepared to fight against loss of memory:
This is the cow. She must be milked every morning so that she will produce milk, and the milk must be boiled in order to be mixed with coffee to make coffee and milk.
Thus they went on living in a reality that was slipping away, momentarily captured by words, but which would escape irremediably when they forgot the values of the written letters.
At the beginning of the road into the swamp they put up a sign that said MACONDO and another larger one on the main street that said GOD EXISTS.
All organisms change the world, in some way or other. However, some organisms change the world consistently in ways that reduce cognitive complexity -- for themselves, for others, or for both. This dissertation examines the mechanisms that lead up to such cognition-directed changes to the world. I am interested predominantly in the human case, but I try to understand the human case in the broader context of other organisms exhibiting such behavior.
Here is an illustrative instance of human world-changing that results in better processing and improved cognitive performance. Cole & Engestrom (1993) reports an experiment by soviet psychologists Vygotsky and Luria on a patient suffering from Parkinson’s Disease (a condition where dopamine deficiency affects the communication between two motor areas of the brain, leading to involuntary movements of some body parts and an inability to execute other movements). The condition of the patient was so severe that he could not walk across the floor. Paradoxically, the patient could climb stairs.
Vygotsky and Luria hypothesized that when the patient was climbing stairs, each stair represented a signal to which the patient had to respond in a conscious way. So if the same signal could be replicated on the floor, the patient should be able to walk. Vygotsky placed pieces of paper on a level floor and asked the patient to walk across the room,
stepping over the pieces. The formerly immobile patient was able to walk across the room unaided.1 This is a striking instance of how altering the world can lead to improved cognitive performance. There are other mundane cases, both in the animal and human world.
• Many animals create structures in the world to reduce their own and others' cognitive complexity. Wood mice (Apodemus sylvaticus) distribute small objects, such as leaves or twigs, as points of reference while foraging. They do this even under laboratory conditions, using plastic discs. Such "way-marking" diminishes the likelihood of losing interesting locations (Stopka & MacDonald, 2003) during foraging. Red foxes (Vulpes vulpes) use urine to mark food caches they have emptied.
This marking acts as a memory aid and helps them avoid unnecessary search (Henry, 1977, reported in Stopka & MacDonald, 2003). Ants drop pheromones to trace a path to a food source. Many mammals mark up their territories. The bower bird creates colorful nests to attract mates (Zahavi & Zahavi, 1997). Many birds advertise their desirability as mates using some form of external structure, like colorful tails, bibs etc. (Bradbury & Vehrencamp, 1998; Zahavi & Zahavi, 1997). Plants emit chemicals to attract pollinators, sometimes even to fight predators (Heiling et al, 2003; Beck, 2001).
Bacterial colonies use a strategy called 'quorum sensing' to know that they have Here is a possible way of framing this result in processing terms. According to Cox (1999), external representations help problem-solving by providing a pathway between two non-linked modules of the brain. Since different modules have access to the same external structure, they can use the structure as a "junction" to form new connections. Parkinson's disease results from a communication breakdown in the brain. It is possible that Vygotsky's paper trail allowed the patient's disconnected brain areas to form a new pathway. This resulted in an improvement in communication between the motor areas, helping the patient walk.
reached critical mass (to attack, to emit light, etc.). This strategy involves individual bacteria secreting molecules known as auto-inducers into the environment. The autoinducers accumulate in the environment, and when it reaches a threshold, the colony moves into action (Silberman, 2003). At the most basic level, cells in the immune system use antibodies that bind to attacking microbes, thereby "marking" them.