Introduction to Psychology - The Brain and Dualism

The Astonishing Hypothesis

  • Francis Crick's astonishing hypothesis: You, with all your experiences and identity, are merely the behavior of a vast assembly of nerve cells and their associated molecules.

    • Essentially, "You are nothing but a pack of neurons."

  • This view is considered odd and unnatural, and many people, initially, do not accept it.

Dualism

  • Dualism is a contrasting doctrine found in religion and philosophy, prominently defended by René Descartes.

  • Descartes questioned whether humans are merely physical machines and concluded they are not, unlike animals, which he considered "beast machines" or robots.

  • Dualism posits that humans consist of:

    • Material bodies (physical).

    • Immaterial souls/minds that possess, reside in, and connect to these bodies.

Descartes' Arguments for Dualism

Argument from Human Action

  • Descartes observed robots of his time (powered by hydraulics) in the French Royal Gardens, noting their reflexive actions.

  • He acknowledged that human bodies also exhibit reflexive actions (e.g., knee-jerk reflex).

  • However, he argued that humans are not limited to reflexive actions; they are capable of:

    • Coordinated.

    • Creative.

    • Spontaneous actions, such as language use.

  • Humans can choose what to say, unlike machines limited to pre-programmed responses.

  • Therefore, humans are not mere machines because of this capacity for choice.

Argument from Doubt (Method of Doubt)

  • Descartes employed a method of doubt, questioning everything he thought he knew:

    • The existence of God.

    • The reality of his country.

    • The genuineness of his relationships.

  • He considered the possibility of an evil demon deceiving him, similar to the modern concept of The Matrix.

  • Descartes even doubted the existence of his own body, noting that madmen sometimes have delusions about their bodies.

  • He questioned whether he was currently dreaming.

  • However, Descartes found one thing he could not doubt: his own thinking.

  • The act of doubting itself proved he was thinking.

  • He concluded that the mind is fundamentally different from the body, leading to his support for dualism.

  • Descartes: “I knew that I was a substance, the whole essence or nature of which is to think, and that for its existence there is no need of any place nor does it depend on any material thing.”

  • The soul is entirely distinct from the body.

Common Sense Dualism

  • Dualism is embedded in our language and intuitions.

  • We speak of owning our bodies and brains, implying a separation.

  • Intuitions about personal identity suggest that someone can remain the same person despite radical bodily changes.

Examples Illustrating Common Sense Dualism

*Movie examples:
* A person waking up in a different body (e.g., a teenager waking up as an older person).
* Reincarnation: A person dying and being reborn in another body.

  • Literary examples:

    • Franz Kafka's The Metamorphosis: Gregor Samsa waking up as an insect.

    • Homer's Odyssey: Odysseus' companions transformed into pigs but retaining their human minds.

  • Multiple personalities occupying a single body (e.g., multiple personality disorder or the movie All of Me).

  • Exorcism: The belief that evil or irrational behavior results from something taking over a person's body.

  • Belief in afterlife: Many religions believe in survival after the body's destruction, with the soul going to heaven, hell, or another body.

Prevalence of Dualistic Beliefs

  • A survey in Chicago found that:

    • 96% of Christians believed they would go to heaven after death.

    • Most Jewish respondents also believed they would go to heaven, despite Judaism's less clear doctrine on the afterlife.

    • Even most people with no religious affiliation believed they would go to heaven.

The Scientific View: Rejection of Dualism

  • The prevailing scientific consensus, as Crick pointed out, rejects dualism.

  • There is no separate "you" distinct from your body, especially your brain.

  • Cognitive scientists, psychologists, and neuroscientists argue: “The mind is what the brain does.”

    • The mind reflects the brain's workings, similar to how computation reflects a computer's operation.

Reasons for Rejecting Dualism

Unscientific Nature of Dualism

  • Dualism fails to provide scientific explanations for:

    • How children learn language.

    • What we find attractive.

    • The basis of mental illness.

  • It posits non-physical causes that are beyond scientific investigation.

Difficulty Explaining the Connection Between Body and Soul

  • Dualists struggle to explain how a physical body connects to an immaterial soul.

  • How does the physical world interact with the non-physical mind?

  • Descartes could not explain how the body obeys the mind's commands or how physical sensations (e.g., pain) affect the mind.

Existence Proof: Machines Can Do Complex Things

  • Descartes believed physical objects could not perform complex tasks like playing chess.

  • However, we now know that machines can:

    • Play chess.

    • Manipulate symbols.

    • Engage in mathematical and logical reasoning.

    • Recognize things.

    • Perform computations.

  • This makes it plausible that humans, too, could be such machines.

Evidence of Brain Involvement in Mental Life

  • Strong evidence links the brain to mental life.

  • Historically, it was known that:

    • Head injuries can alter mental faculties.

    • Diseases like syphilis can cause derangement.

    • Chemicals like caffeine and alcohol affect thinking.

  • New evidence includes:

    • Brain imaging techniques (CAT scans, PET, fMRI) showing direct correlations between brain activity and mental processes.

      • Different brain regions are active when seeing, hearing, reading, or generating words.

      • Brain activity patterns can reveal whether someone is thinking about music or sex.

      • Brain activity patterns can reveal whether someone is working through a moral dilemma.

  • These findings support the view that mental life is a product of brain activity.

The Brain: A Disgusting Meatloaf?

  • Despite its crucial role, the brain appears as a rather unappealing "old meatloaf."

    • Gray matter (when removed from the head).

    • Bright red inside the head due to blood flow.

    • Doesn't taste good.

  • This raises the question: How can something so seemingly mundane give rise to consciousness, free will, and love?

  • The goal of neuroscience is to demystify this process.

The Neuron: Basic Building Block of Thought

  • The neuron is the basic unit of the brain.

  • Typical neuron consists of:

Dendrites

  • Little tentacles that receive signals from other neurons.

  • Signals can be excitatory (increase the likelihood of firing) or inhibitory (decrease the likelihood of firing).

Cell Body

  • Sums up the signals arithmetically.

  • If the sum reaches a certain threshold (e.g., +60), the neuron fires.

Axon

  • A long fiber that transmits the electrical signal.

  • Can be several feet long (e.g., from the spinal cord to the big toe).

Myelin Sheath

  • Insulation surrounding the axon that speeds up firing.

Neuron Facts

  • Approximately one thousand billion neurons in the brain.

  • Each neuron connected to thousands or tens of thousands of other neurons.

  • Neurons come in three types, sensory, motor, and interneurons.

Sensory Neurons

  • Take information from the external world.

  • Example: Neurons firing in the retina when seeing something.

Motor Neurons

  • Tell muscles what to do.

  • Example: Neurons firing when raising a hand.

Interneurons

  • Connect sensory and motor neurons.

  • Responsible for thinking and making connections.

Neurons do not regrow

  • New research suggests that neuron regrowth can occur in certain parts of the brain.

All or Nothing Principle

  • A neuron either fires or doesn't; the intensity of the trigger doesn't affect the firing strength.

  • Like a gun, squeezing the trigger harder doesn't make it fire faster or harder.

  • Coding intensity is achieved through The number of neurons firing, the more intense, and frequency of firing.

Synapses and Neurotransmitters

  • Neurons communicate chemically, not through direct wiring.

  • Between neurons is a tiny gap called a synapse (about one ten-thousandth of a millimeter wide).

  • When a neuron fires, it sends chemicals (neurotransmitters) across the synapse to affect the dendrites of the next neuron.

  • Neurotransmitters can be excitatory or inhibitory.

  • Psychopharmacology involves manipulating neurotransmitters.

Agonists

  • Increase the effect of neurotransmitters by:

    • Making more neurotransmitters.

    • Stopping the cleanup of neurotransmitters.

    • Mimicking neurotransmitter effects.

Antagonists

  • Slow down the amount of neurotransmitters by:

    • Destroying neurotransmitters.

    • Making it hard to create more neurotransmitters.

    • Blocking neurotransmitter receptors on dendrites.

Examples of Drugs and Neurotransmitters

  • Curare (antagonist): Blocks motor neurons, causing paralysis and death.

  • Alcohol (inhibitory): Inhibits inhibitory parts of the brain (frontal lobes), leading to disinhibition; higher doses inhibit excitatory parts, causing passing out.

  • Amphetamines: Increase arousal by increasing norepinephrine.

  • Prozac: Increases serotonin levels, potentially alleviating depression.

  • L-dopa: Increases dopamine, alleviating Parkinson's symptoms.

Brain Wiring and Parallel Processing

  • The brain is not wired like a typical computer.

  • The brain is highly resistant to damage unlike a computer, and it is also extremely fast.

  • The brain works through parallel processing or massively parallel distributed processing.

  • Research aims to create computers that mimic brain functions through massively distributive networks (neural networks).

Neural Networks

  • Computational networks inspired by the structure of neurons.

  • Used to build smart machines modeled after brains.

  • Still a young field, with no machine yet capable of human-level face recognition, language understanding, or general intelligence.

  • The human brain is wired in an extraordinarily more complicated way than any sort of simple neural network.

Parts of the Brain

  • Some functions don't require the brain

  • Brain isn't needed for everything such as newborn Sucking, Limb Flexation, Extension of the penis, and Vomiting.

  • The brain's functions involve both low-level internal structures (subcortical structures) and the cortex.

Subcortical Structures

  • Located beneath the cortex.

    • Medulla: The medulla is responsible for heart rate and respiration (damage can be fatal).

    • Cerebellum: Responsible for body balance and muscular coordination (contains approximately 30 billion neurons).

    • Hypothalamus: Responsible for feeding, hunger, thirst, and sleep.

The Cortex

  • The outer layer of the brain. The cortex is where all the neat stuff takes place.

  • Crumpled to increase surface area.

  • If flattened, it would be about two feet square.

  • Primates and Humans have a lot; it consists of 80% of human brain volume.

  • Divided into lobes: The frontal lobe, parietal lobe, occipital lobe, and temporal lobe.

Topological Maps in the Cortex

  • The lobes contain maps of the body, revealed through experiments involving electrical stimulation.

  • Stimulating different parts of the brain causes movements or sensations in corresponding body parts.

  • Maps exist in the motor cortex (motor control) and sensory cortex (somatosensory function).

Characteristics of Cortical Maps

  • Topographical: Body parts close together are also close together on the brain map.

  • Size Representation: Body part size in the brain corresponds to the degree of motor command or sensory control, not actual size.

  • Much of the cortex is not projection areas, but rather contains areas for language, reasoning, and moral thought.

Studying Brain Function

  • Imaging methods (CAT scan, PET scan, fMRI) reveal brain activity during tasks.

  • Studying brain damage (lesions, tumors, strokes, injuries) helps understand the function of damaged areas.

Types of Brain Damage and Their Effects

  • Apraxia: Inability to coordinate movements & damage to Motor control (waving goodbye, lighting a cigarette), despite intact motor abilities.

  • Agnosia: Loss of ability to recognize certain things, Psychic blindness.

  • Visual agnosia: Inability to recognize objects.

  • Prosopagnosia: Inability to recognize faces.

  • Sensory neglect: Neglect of one side of the body or world.

  • Aphasia: Language disorders.

  • Broca's aphasia: Inability to speak fluently.

  • Receptive aphasia: Fluent but nonsensical speech, inability to understand others.
    Acquired psychopathy: Inability to distinguish right from wrong due to damage to frontal

Hemispheric Specialization

  • The brain appears symmetrical but is not.

  • Right-handed people (90% of the population) typically have language in their left hemisphere.

  • Lateralization: Some Functions are found dominantly on one side of the other. Language in the Left. math and music on the right.

Hemispheric Connections and Crossover

  • Everything seen in the left visual field goes to the right brain hemisphere.

  • Everything seen in the right visual field goes to the left brain hemisphere.

  • The right hemisphere controls the left side of the body and vice versa.

  • The two halves are connected by the corpus callosum.

Split-Brain Studies

  • Studying individuals with bisected brains (severed corpus callosum) reveals hemispheric differences.

Humility and the Hard Problem of Consciousness

  • Psychology aims to understand the mind as an information processor.

  • However, the "hard problem of consciousness" remains.

  • How do subjective experiences and feelings arise from physical processes?

  • How does a brain give rise to subjective sensations?

The Mechanistic Conception of Mental Life

  • Psychology seeks to explain mental life mechanistically rather than mystically.

  • This approach may conflict with humanist values such as free will, responsibility, intrinsic value, and spiritual value.

Responses to the Tension Between Mechanism and Humanism

  • Reject the scientific conception of the mind (embrace dualism).

  • Reject humanist values (claim they are illusions).

  • Reconcile scientific and humanist perspectives.

  • The tension between these views will be a recurring theme throughout the course.