Lecture Notes: Computational Theory of Mind and Brain
Introduction
- Topic: Mars Computational Theory Level of Analysis
- Focus: Color vision as a case study
- Agenda: 1) Discuss color vision in terms of computational theory 2) Methods in cognitive neuroscience, focusing on face perception
Key Themes
- Big Question: How does the brain give rise to the mind?
- Physical Basis of the Brain: Previous lectures addressed the brain's physical structure.
- Defining the Mind:
- The mind is viewed as a set of computations that extract representations.
- Mental representations can be perceptual (e.g., seeing motion) or conceptual (e.g., thoughts).
David Marr's Framework
- Marr's Big Idea: Understand what is computed and why at the level of computational theory.
- Example of Vision:
- Light enters the eyes, leading to perception.
- Goal: Understand how computations convert light (input) to perception (output).
Ill-posed Problems in Perception
- Color Vision Problem:
- Determining an object's color (reflectance) from the light it reflects (luminance) can be ill-posed.
- Solution involves making assumptions about the light illuminating the object.
- Other Examples:
- Shape perception is also an ill-posed problem: multiple shapes can cause the same retinal image.
- Language and meaning can be ill-posed (e.g., ambiguous words).
Computational Theory in Color Vision
- Using Color: Color helps in identifying objects (e.g., fruit) and their properties.
- Ill-posed Nature: We often lack enough information to deduce color directly; need additional context.
- Assumptions and Knowledge: Necessary to deduce color from luminance.
Levels of Analysis
- Computational Theory: What is computed and why?
- Algorithm and Representation: What is the code to solve the computational problem?
- Hardware: Neural basis of the computations (e.g., neurons involved in color perception).
Psychophysics and Behavioral Studies
- Psychophysics: Assessing how people perceive different stimuli and their properties.
- Demo on Color Recognition: Different colored cars perceived as different colors despite being the same color due to context cues.
Face Perception Case Study
- Importance of Face Recognition:
- Vital for social interactions; conveys identity, mood, and other personality traits.
- Example: Jacob's experience with prosopagnosia (face blindness).
- Questions in Face Recognition:
- How does face recognition differ from object recognition?
- What computational processes are involved?
Tools for Face Recognition Research
- Behavioral Data: Reveal how we recognize faces based on experience and familiarity.
- Functional MRI:
- Measures brain activity based on blood flow changes (BOLD signal).
- High spatial but low temporal resolution.
- Useful for comparing brain responses to faces versus objects.
Conclusion
- Understanding the computational theory of mind requires multiple levels of analysis and diverse methods.
- Face perception remains a rich field of study with ongoing research to understand the neural basis and computational mechanisms involved.
Note: Further readings and assignments on functional MRI and cognitive neuroscience methods will be provided next class.