CHAPTER FIVE The Bayesian Brain Flashcards
What theorem is the basis of perception and consciousness according to the text?
Bayes’ theorem
Bayes’ theorem is a mathematical formula used for calculating conditional probabilities.
According to Anil Seth, what type of information do brains work with?
Ambiguous sensory information
This refers to sensory data that can be interpreted in multiple ways.
What does the brain do with sensory information according to the Bayesian brain model?
Build predictions of the world
This involves integrating sensory information with internal models.
What are the three components of Bayesian reasoning as applied to the brain?
Priors, likelihoods, posteriors
Priors are initial beliefs, likelihoods are evidence from senses, posteriors are updated beliefs.
What philosophical idea does Plato’s allegory of the cave illustrate about perception?
We perceive a shadow of reality, not reality itself
The allegory suggests that our understanding is limited by our sensory experiences.
Who first proposed a modern theory of visual perception?
Abu Ali al-Hasan Ibn al-Haytham (Alhazen)
Alhazen is known for his work on the nature of light and vision.
What distinction did Immanuel Kant make regarding knowledge and perception?
Phenomena vs. noumena
Phenomena are our perceptions, while noumena are things in themselves, which are unknowable.
What did Hermann von Helmholtz discover about nerve signal speed?
Nerve signals travel slowly, about 165 feet per second
This contradicted the assumption that nerve signals travel instantaneously.
What is the concept of ‘unconscious inferences’ as described by Helmholtz?
The mind builds a 3D model of the world from sensory information
This refers to the brain’s process of interpreting sensory data to create a coherent perception.
According to Richard Gregory, how does the brain handle perception?
Perceptions are hypotheses tested against sensory evidence
Gregory compared this process to scientific hypothesis testing.
What is the ‘Necker cube’ an example of?
Ambiguity in perception where two interpretations are possible
The Necker cube can be perceived from two different perspectives.
Fill in the blank: The brain’s task is not to see the retinal image, but to relate signals from the retina to _______.
objects of the external world
This highlights the brain’s role in interpreting sensory data.
What phenomenon became a viral sensation related to color perception?
The Dress
This was an internet debate about whether a dress was blue and black or white and gold.
What does Adelson’s checker-shadow illusion demonstrate?
How perception can be influenced by context and lighting
This illusion shows how shading affects the perception of color.
True or False: According to the text, perception is a direct reflection of reality.
False
The text argues that perception is constructed by the brain and not a direct experience of reality.
What is the Adelson’s checker-shadow illusion?
A visual illusion showing two squares (A and B) that appear different in color due to shadowing, despite being the same shade.
Created by Edward Adelson, it demonstrates how our brain generates hypotheses based on visual context.
What does the term ‘hypothesis generation’ refer to in perception?
The process by which the brain forms predictions about sensory input and tests them against reality.
This can lead to perceptual errors when the brain’s assumptions conflict with actual sensory data.
How does Bayesianism relate to color perception?
Bayesianism explains how prior knowledge and expectations influence our interpretation of sensory information, like color.
Strong priors can affect how we perceive colors under different lighting conditions.
What is the ‘hollow mask’ illusion?
An illusion where a concave mask appears convex due to strong prior expectations that faces are outward-facing.
This phenomenon highlights the power of prior beliefs in shaping perception.
What was the role of prior probabilities in perceiving ‘The Dress’?
Different prior probabilities led people to perceive the dress as either blue and black or white and gold based on their expectations of lighting conditions.
The actual color was revealed to be blue and black.
What did Richard Fitzhugh’s experiment involve?
He attempted to determine what a cat was seeing by analyzing nerve impulses from its retina.
This experiment aimed to understand the correlation between neural signals and visual perception.
How does the brain process sensory information according to the intuitive model?
It relies on bottom-up signals that build a perception of reality from basic features like color and shape.
This model suggests that perception is a straightforward reception of sensory data.
What is the modern understanding of how the brain perceives reality?
The brain constructs a 3D model of the world, predicting and hallucinating sensory experiences rather than simply receiving them.
This process involves both bottom-up and top-down information flow.
What is ‘prediction error’ in the context of perception?
The difference between expected sensory input and actual sensory input, used by the brain to update its model of reality.
Minimizing prediction error is crucial for maintaining an accurate perception of the world.
What is a Kalman filter?
An algorithm used to estimate unknown quantities based on measurements and predictions, analogous to how the brain processes sensory information.
It updates predictions based on new data, similar to how the brain adjusts its model of reality.
How do different sensory modalities contribute to perception?
The brain integrates information from multiple senses, including vision, hearing, touch, and internal body states, to form a cohesive perception.
This integration is part of the brain’s Bayesian processing system.
What is the relationship between consciousness and Bayesian inference according to neuroscientists?
Consciousness is viewed as a model of the world based on Bayesian inference, where predictions about sensory data shape our experiences.
Anil Seth and Chris Frith emphasize that our conscious experience is not a direct reflection of reality but rather a predictive model.
Fill in the blank: According to Chris Frith, ‘Consciousness is our model of the _______.’
world.
True or False: The brain processes sensory information strictly through bottom-up signals.
False.
What is consciousness described as in the context of predictions?
Consciousness is Bayesian
This indicates that our conscious experience is shaped by probabilistic predictions.
What is the role of dopamine in the context of prediction and reward?
Dopamine is involved in signaling prediction errors and reward expectations
It acts as a neurotransmitter with a complex relationship to reward and pleasure.
What experiment demonstrated how humans integrate information from different senses?
Subjects estimated the width of a ridge using both vision and touch through a mirror setup
This experiment highlighted the Bayesian integration of sensory information.
How do humans respond when visual input is noisy, according to the experiment mentioned?
Subjects rely more on touch when visual input is noisy
This reflects the Bayesian approach to sensory integration.
What is the McGurk effect an example of?
The McGurk effect demonstrates how visual information can override auditory information
It shows the brain’s integration of conflicting sensory inputs.
What happens to dopamine activity when a reward is expected but does not materialize?
Dopamine activity drops below baseline levels
This indicates a disappointment in the prediction of reward.
What is the primary function of the brain in relation to predictions?
The brain aims to minimize prediction errors
It constantly checks predictions against incoming sensory data.
Fill in the blank: The more _______ the predictions, the more attention the brain pays to them.
precise
High-precision predictions are prioritized in sensory processing.
What is predictive processing?
A model describing how the brain predicts the effects of its own movements and gathers information
It emphasizes the interconnectedness of perception and action.
What two challenges does the predictive brain face according to the text?
- Predicting the effects of its own movements
- Predicting the best move to gain information
These challenges highlight the active role of the brain in perception.
What does it mean when the brain receives high-precision sense-data that contradicts a prediction?
It triggers a prediction error or ‘surprisal’
This results in a strong signal sent to higher levels of processing.
True or False: The brain only processes information passively.
False
The brain actively seeks and processes information through movements and predictions.
What is the relationship between predictions and actions according to the text?
Actions are driven by predictions about how to achieve desired outcomes
This underscores the predictive nature of motor control.
What is the direct sense in which action requires prediction?
The brain has to predict which sequence of nerve firings will perform an action.
What are the two models of action discussed?
- Inverse model
- Forward model
What does the inverse model do?
It signals which actions to send to the muscles to achieve a goal.
What does the forward model do?
It calculates what will happen given the signals sent to the muscles.
How do the inverse and forward models interact?
They work in parallel, checking predictions against each other.
What is one way we can learn according to the text?
By imagining ourselves performing a task and predicting the outcomes.
What prediction does the brain make when we move?
It predicts the sensations we will experience from that movement.
Fill in the blank: The brain subtracts expected movements from the movements it receives from _______.
the world
What is an example given to illustrate gathering information?
Playing Wordle to guess a five-letter word.
What strategy is employed when playing Wordle?
Gathering information by guessing words with common letters.
What is the Bayes-optimal move in the context of guessing?
The guess that reduces the search space the most.
What is the significance of saccades in perception?
They allow the brain to predict where important visual information will be.
How do saccades differ from a bottom-up model of perception?
They are directed to expected future locations of action rather than salient points.
What is a key finding about expert vs novice observers in sports?
Experts make more precise predictions about where action will occur.
Why can’t most people tickle themselves?
The brain predicts the sensations from self-induced movements and discounts them.
Fill in the blank: People with _______ may be able to tickle themselves.
schizophrenia
What does the brain do with highly predictable sensory signals?
It subtracts them from the sense of the world.
What is the effect of unexpected changes in predictable sounds?
They become noticeable because they disrupt the predictions.
What did the experiment with touch demonstrate?
People overestimate the force used by others when trying to match it.
What happens when two players take turns pressing a button in the described experiment?
Players overestimate the force used by their opponent, leading to escalating pressure each turn.
How does the use of a joystick affect players’ ability to judge force?
Players get better at correctly judging how much force they are using when controlling the device with a joystick.
What is the reason people cannot tickle themselves?
The brain predicts the sensations with high precision, suppressing the response.
What is the ‘hollow mask’ illusion used for in relation to schizophrenia?
It can be a diagnostic tool, as about 30% of schizophrenic people see through the illusion.
What characterizes the predictions of people with schizophrenia compared to neurotypical individuals?
Schizophrenics have weaker priors, leading to less precise predictions of the world.
What phenomenon do patients with schizophrenia often report regarding their body movements?
They feel their body is under the control of an outside force.
How does the Bayesian model explain auditory hallucinations in schizophrenia?
Patients hear their internal monologue as if it were an external voice, due to the lack of prediction suppression.
Why might schizophrenics experience visual disturbances more acutely than neurotypical individuals?
They do not suppress minor prediction errors due to weaker priors, leading to bizarre hypotheses.
What is suggested about tickling and schizophrenia?
People with schizophrenia might be able to tickle themselves due to less precise predictions of sensory data.
What is the metaphor used to describe the belief landscape in the Bayesian model of depression?
A landscape of rolling hills and valleys, where beliefs are represented as ‘valleys’ that one wants to navigate.
What happens when a depressed person’s prior beliefs are inappropriately strong?
They become stuck in a ‘local hole’ of beliefs that do not accurately reflect reality.
How do psychedelics like psilocybin potentially affect depression according to the Bayesian model?
They may flatten the belief landscape, weakening inappropriately strong priors.
What type of trial is difficult to conduct with psychedelic drugs, and why?
A double-blind trial, because patients may know they are receiving treatment due to the effects.
What is the excessive precision-weighting of priors in relation to depression?
It refers to being overly confident in negative beliefs about oneself.
Fill in the blank: The researchers used a clever trick by giving the control group a tiny dose of _______.
psilocybin
What do psychedelics do to the way individuals perceive familiar things?
They make the world feel unfamiliar and increase interest in sensory data.
What is a potential risk when using psychedelics for treating depression?
The possibility of moving into a less true belief valley, leading to delusions.
What is one societal challenge mentioned regarding the use of psychedelics in treatment?
It is difficult to obtain licenses for research, and prescribing them is illegal in many places.
What are the societal and regulatory obstacles regarding psychedelics as psychiatric drugs?
Difficult to obtain research licenses and prescribing them is illegal in the US and the UK.
Who is a pioneer of the predictive processing/Bayesian brain model?
Karl Friston.
What does the predictive processing model explain?
How we make sense of ambiguous nerve signals and gather information.
According to Friston, what is our fundamental motivation?
Minimizing prediction error.
How does Friston describe the fundamental driver of all life?
A struggle to reduce the difference between top-down predictions and bottom-up sense-data.
What does the term ‘free energy’ refer to in Friston’s model?
Prediction error.
What happens if a living organism does not maintain a boundary between itself and the universe?
It would die.
What is the difference between homeostasis and allostasis?
- Homeostasis: Adjusting surroundings to maintain stable internal environment. * Allostasis: Planned behavior to avoid homeostatic corrections.
What are examples of deeply wired priors that Friston mentions?
- Blood sugar levels * Body temperature * Oxygen levels * Bodily integrity
What is ‘motor babbling’ in babies?
Trying out random nerve signals to learn about their body and the world.
How do humans differ from simpler organisms in terms of prediction?
Humans have hierarchically deeper generative models and can look further into the future.
What is the role of desires in Friston’s free energy model?
Desires and predictions are treated as the same in minimizing prediction error.
What does Friston mean by saying we are ‘crooked scientists’?
We seek to minimize prediction errors while having hardwired priors that cannot change.
True or False: According to Friston, we are purely truth-seeking and curious.
False.
What does Friston suggest about the framework of free energy?
It allows you to simplify the model and use one term for everything.
Fill in the blank: According to Friston, minimizing free energy also means trying to find out as much as you can about the world in order to _______.
[make better predictions]
What is the significance of prediction error in living systems?
Living systems must minimize prediction error to survive.
What fields are mentioned in relation to the authors of the paper?
Psychology, neurobiology, and developmental biology
What is the likelihood that three authors of one paper all have famous scientist relatives?
Astronomically low based on the base rate of famous scientists in the population
How does the likelihood change when considering family jobs?
Somewhat higher due to jobs often running in families
What is noted as strange about people’s internal monologue?
Apparently not everyone has an internal monologue
Under what conditions was psilocybin administered?
Under careful laboratory conditions, medical supervision, and alongside therapy
What kind of depression were the participants suffering from?
Long-standing, serious depression that had not responded to treatment
Should individuals self-treat mental health conditions with psilocybin from informal sources?
No, it is advised against treating mental health conditions with psilocybin obtained from informal sources
