Agenda Pomona College LCS 11: Cognitive Science argument Jesse A. Harris February 25, 2013 Turing test review Searle s argument GQ 2.3 group discussion Selection of responses What makes brains special? TED talks for next class Cynthia Breazeal: The rise of personal robots David Hanson: Robots that show emotion Jesse A. Harris: LCS 11: Cognitive Science, argument 1 Jesse A. Harris: LCS 11: Cognitive Science, argument 2 Turing test Behavior and functionalism The question Can machines think? to be replaced with a less ambiguous formulation: Could some conceivable digital computer perform well in the imitation game. Functionalist slogan What matters is the software, not the hardware; cognitive systems are multiply realizable. Behavior All that matters is that the machine emulates the appropriate behavior of a human. Jesse A. Harris: LCS 11: Cognitive Science, argument 3 Jesse A. Harris: LCS 11: Cognitive Science, argument 4
Varieties of AI Weak AI Use computer in the study of mind is merely a useful tool. Strong AI With the right set of programs, a computer understands and may have genuine cognitive states. More on this next class! Searle s slogan The mind is not a computer program. Searle uses a thought experiment designed to show that the thesis of Strong AI results in absurdity if taken seriously. Jesse A. Harris: LCS 11: Cognitive Science, argument 5 Jesse A. Harris: LCS 11: Cognitive Science, argument 6 Searle doesn t understand a word of Chinese All he has done is manipulate the formal symbols Has no real understanding of Chinese or the task. Problem is inherent to formal computers: no meaning associated with the syntax. Jesse A. Harris: LCS 11: Cognitive Science, argument 7 Jesse A. Harris: LCS 11: Cognitive Science, argument 8
GQ 2.3 Group discussion Open question What does Searle mean by syntax? How about semantics? First, is Searle a functionalist? A physicalist? Or something in between? Second, what do you think Searle mean when he says that brains cause meaning? Do you agree or disagree with this assertion? Defend your answers concretely. Group leaders: Shalina, Thomas, Paul, Orren, Joel, Cole, Juliana, Mary Margaret, Natasha Jesse A. Harris: LCS 11: Cognitive Science, argument 9 Jesse A. Harris: LCS 11: Cognitive Science, argument 10 Some objections Systems reply (c) It s not the individual who understands Chinese, but the entire system. Even if the were internalized - so that the English rule book only formed a subpart of the system, we ve still provided no way to attach meaning to the symbols the subsystem manipulates. The robot reply (f) Insert a computer into an autonomous robot, so that it could interact with the world. Adds a set of causal relations with the world, but still don t have any understanding as long as the formal inputs and outputs go uninterpreted. Jesse A. Harris: LCS 11: Cognitive Science, argument 11 Jesse A. Harris: LCS 11: Cognitive Science, argument 12
The brain simulator reply (g) Change the character of the computational system so that it simulates the neuronal firings in the brain. 1. Problematic for the basis thesis of functionalism shouldn t have to know anything about how the brain works to understand cognition. 2. Simulates wrong things about the brain: modeling the computational properties of the brain still won t give us intentionality, because we can t simulate causal properties. The other minds reply Only know other minds via their behavior - can t verify that machines or people really understand something outside of their behavior. What else is there? (= flat-out rejection) It is no answer to this argument to feign anesthesia. In cognitive sciences one presupposes the reality and knowability of the mental in the same way that in physical sciences one has to presuppose the reality and knowability of physical objects. (from original 1980 paper, p.422l) Jesse A. Harris: LCS 11: Cognitive Science, argument 13 Jesse A. Harris: LCS 11: Cognitive Science, argument 14 Many mansions reply Eventually, the technology will develop so that we can build in the necessary causal processes for intentionality. 1. Crucially weakens Strong AI thesis that mind is a formal symbol manipulating device. 2. No purely formal system could ever give rise to cognitive states, because it necessarily lacks real causal import, except to cause the next set of formal processes. Against symbol-pushing The argument in brief: 1. Programs are purely formal (syntactic). 2. Human minds have mental contents (semantics). 3. Syntax by itself is neither constitutive of, nor sufficient for, semantic content. 4. Therefore, programs by themselves are not constitutive of nor sufficient for minds. Jesse A. Harris: LCS 11: Cognitive Science, argument 15 Jesse A. Harris: LCS 11: Cognitive Science, argument 16
Wetware and mental contents Dependence on brains... mental phenomena might be dependent on actual physical-chemical properties of actual human brains. Intrinsic connection between the wetware (brain) and the kinds of functions it performs, namely, cognitive states. Intentionality Whatever else intentionality is, it is a biological phenomenon, and it is as likely to be as causally dependent on the specific biochemistry of its origins as lactation, photosynthesis, or any other biological phenomena. Simulation and duplication Simulation: all you need for simulation is the right input and output and a program to get from input to output. No one would mistake a simulation of digestion for the real thing. Brains are specific biological organs, and their specific biochemical properties enable them to cause consciousness and other sorts of mental phenomena. Computer simulations of brain processes provide models of the formal aspects of these processes. But the simulation should not be confused with duplication. (Searle, 1990:29R) Jesse A. Harris: LCS 11: Cognitive Science, argument 17 Jesse A. Harris: LCS 11: Cognitive Science, argument 18 Simulation and duplication Open discussion What about an artificial organ? Artificial hearts can be hearts, despite being constructed of a different set of materials. Does Searle s point still stand? What s different between the case of artificial hearts and the mind? 1. Are you convinced by the argument? 2. Do we have to give up Strong AI? 3. What about Searle s positive views regarding intentionality and the brain? Do you find those convincing? 4. What other metrics do we have for determining whether an individual is capable of conscious thought or genuine mental states? Jesse A. Harris: LCS 11: Cognitive Science, argument 19 Jesse A. Harris: LCS 11: Cognitive Science, argument 20