Decisions and the Brain

What Is a Decision?
In order to be able to scientifically measure decision-making, we define decisions as "taking an action." There are multiple decision-making systems within each of us. The actions we take are a consequence of the interactions of those systems. Our irrationality occurs when those multiple systems disagree with each other.

The Tale of the Thermostat
Your brain is a decision-making machine, a complex but physical thing. Like any physical process, there are multiple ways in which decisions can go wrong. Being a physical being does diminish who you are, but it can explain some of the irrational choices you make.

The Definition of Value
Value measures how much one is willing to pay, trade, or work for a reward, or to work to avoid a punishment. Value is not intrinsic to an object, but must be calculated anew each time. This produces inconsistencies, in which different ways of measuring value can produce different orderings of one's preferences.

Value, Euphoria, and Do-It-Again Signal
Pleasure and value are different things. One can have pleasure without value and value without pleasure. They are signaled by different chemicals in the brain. In particular, the brain contains a signal for "better than expected," which can be used to learn to predict value. The lack of expected reward and the lack of expected punishment are separate processes (disappointment, relief) that require additional neural mechanisms.

Risk and Reward
Defining decision-making in terms of action-selection creates the potential for decisions that are illogical from a value-based perspective. The mammalian decision-making components, which can produce conflict between action options.

The Decision-Making System

Multiple Decision-Making Systems
There are multiple neural systems that drive decision-making, each of which has different computational properties that make it better suited to drive action-selection systems under different conditions. We will identify four action-selection systems: Reflexes, Pavlovian, Deliberative, and Procedural. Along with motoric, perceptual, situation-categorization, and motivational support systems, these make up the decision-making system.

Reflexes
A reflex is a decision-making system because it includes taking an action. A reflex entails a simple response to a stimulus based on a rule learned over long, evolutionary timescales. Although reflexes can change within a lifespan, those changes are either predetermined genetically (as animals change from children to adults) or entail only very simple learning processes (limited primarily to habituation and adaptation effects).

Emotion and the Pavlovian Action-Selection System
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Deliberation
Some decisions are made by explicitly imagining the potential consequences of that decision. This imagination process is particularly good for decisions that cannot be learned slowly over time, or for major decisions that require a large upfront commitment cost. Deliberation is a computationally expensive process that requires a number of neural systems, including attention, imagination, and evaluation processes, and as such takes time to calculate which action to take.

The Habits of Our Lives
With enough experience, action-selection becomes "cached" or stored in stimulus-response pairs and response-action chains. The advantage of this system is that it can respond quickly and reliably, with the same action-sequence every time. The disadvantage of this system is that it is inflexible and is slow to change in response to changing conditions.

Integrating Information
Although our senses receive physical information from the world, we interpret those senses in terms of the objects in the world--we see a tree, we feel the wind, we hear a bird. Interpreting that information requires an integration process that takes time. We can trade off time for accuracy if need be.

The Stories We Tell
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Motivation
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The Tradeoff Between Exploration and Exploitation
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Self-Control
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The Brain with a Mind of its Own

The Physical Mind
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Imagination
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Addiction
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Gambling and Behavioral Addictions
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Post-Traumatic Stress Disorder
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Computational Psychiatry
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The Human Condition

What Makes Us Human?
Humans are animals with unique abilities, particularly in the realms of language, imagination, and culture. However, like our physical bodies, our mental abilities contain echoes of our related mammalian cousins. Like our decision-making systems, our tremendous abilities have precursors in other animal behaviors.

The Science of Morality
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The Conundrum of Robotics
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