Minds and Machines

Summer 2011Thursday, 8/4

Modules• Dissociable functional components, e.g. stereo

speakers, keyboards.• Mental modules are: isolable function-specific

processing systems, whose operations are mandatory, which are associated with specific neural structures, and whose internal operations may be both encapsulated from the remainder of cognition and inaccessible to it.

• Cognitive Architecture: The basic structural organization of the mind.

Modest Modularity• Positive Claim: input systems, or mechanisms

that “present the world to thought”, as well as systems that are involved in language production/comprehension, are modular.

• Negative Claim: Central systems, such as systems involved in belief fixation and practical reasoning, are not modular.

• On this view, the mind is akin to a general purpose computer that’s equipped with a limited number of special purpose modules.

Massive Modularity: “Bag of Tricks” view

• Claims that the mind is modular through and through, including the parts responsible for high-level cognition functions like belief fixation, problem-solving, planning, and the like.

• “Intelligence does not depend on the translation of incoming information into some unitary inner code that’s operated on by general purpose logical inference. Instead, we confront a mixed bag of relatively special-purpose encodings and strategems whose overall effect is to support the particular needs of a certain kind of creature occupying a specific environmental niche.” (Clark)

Biological Arguments for the Bag of Tricks View

1. Biological systems are designed systems, constructed incrementally (by a process of tinkering). 2. Such systems, when complex, need to have massively modular organization. 3. The human mind is a biological system, and is complex. C. So the human mind will be massively modular in its organization.

1. Animal minds are massively modular.2. Human minds are incremental extensions of

animal minds.C. So human minds are massively modular.

Biological Arguments for the Bag of Tricks View

Reason to be weary of adaptationist accounts of the mind: Spandrels

1. Minds are computational problem solving devices.

2. There are specific types of solutions to specific types of problems (a single general type of problem is incoherent!).

C. So for minds to be (successful) general problem solving devices, they must consist of collections of specific problem solving devices, i.e. many computational modules.

A priori Argument for the Bag of Tricks View

Coordination Problem

• How does the “bag of tricks” view account for large scale coherent behavior?

Cricket Phonotaxis

• Phonotaxis: the capacity to detect and reliably move towards a specific sound or signal.

• The male cricket produces a song of a specific rhythm (indicative of species) and tone (indicative of fitness).

• The female cricket detects and moves towards the loudest cricket around.

• From a design standpoint, it is tempting to decompose the female cricket’s task into these steps:

1. Hear and identify the song of her own species.2. Localize the source of the song.3. Move towards it.

Cricket Phonotaxis

What actually happens:1. The cricket’s ears are joined by a

tube, so that each ear receives sounds via two routes.

2. Simple neural circuitry compares the out-of-phase sound waves, yielding a vibration of greater amplitude at the ear nearest the sound source.

3. Two neurons are connected to each ear and fire when vibration amplitude reaches a critical level.

4. The neuron connected to the ear nearest the sound source reaches the threshold first and causes to turn the cricket to its side.

Cricket Phonotaxis

• Webb (et all) built a simple robot-cricket that performs the same task.

• The robot does not build a rich model of its environment and then apply complex analysis to generate an action plan.

• Its operation can be explained purely on the implementational level without talking about computations or mental representations or anything like that.

• But these simple operations yield what, from a distance, seems like highly complex, intelligent action.

Cricket Phonotaxis

Boid Flocking Behavior• Each boid (a simple unit) follows three rules:

1. Try to stay near a mass of other boids.2. Avoid getting too close to any one neighbor.3. Match your velocity to that of your neighbors.

• When each boid followed these simple rules, pattens of on-screen activity ensued that closely resembled the flocking behavior of real flocks of animals (fish, birds, etc.).

Termite Nest Construction• In building nests,

termites follow two simple strategies:1. Rolling mud into a ball and impregnating it with a chemical trace.2. Picking up the balls and depositing them wherever the trace is stronger.

Fodor’s against massive modularity

• Nomic vs. non-nomic properties.• Inference vs. simple sensory transducability.• Abductive inference.