Podcast Summary: That Neuroscience Guy

Episode: The Neuroscience of Making Fast or Slow Decisions

Host: Olaf Krigolson
Date: December 1, 2025

Overview of the Episode

In this episode, Olaf Krigolson explores the neuroscience behind how we make fast and slow decisions in everyday life. Building upon recent discussions about decision models and the exploration-exploitation dilemma, Krigolson delves into the “System One/System Two” theory of thinking, examines how these systems function in the brain, and discusses his perspective on the nature of decision processes. Offering relatable examples and a concise summary of cognitive theories, the episode provides a digestible yet insightful look into the underpinnings of human choice.

Key Discussion Points & Insights

1. Recap of Previous Concepts (02:00–05:30)

• Stages of Decision-Making:
  • Representation phase: Identify the set of feasible actions by considering both internal and external states.
  • Valuation phase: Assign a value to each possible action.
  • Action selection: Choose an action based on valuations (or decide to explore).
  • Outcome evaluation and learning: Assess the outcome and update future decisions accordingly.
• Noted that learning will be revisited in future episodes, while this episode focuses on decision speed and style.

"Representation, valuation, action selection, and outcome evaluation." (04:20)

2. Introduction to Fast and Slow Decision Systems (05:30–08:00)

• Decision making isn’t captured by a single model—multiple systems are involved.
• Revisits the System One/System Two theory, made popular by Daniel Kahneman’s "Thinking Fast, Thinking Slow".
  • System One: Rapid, instinctive, gut hunch-driven responses.
  • System Two: Deliberative, rational, thought-out choices.

“System one is your gut hunch system where you make these very sort of rapid gut hunch responses. And system two is a more analytical system where you, you make a more rational thought out choice.” (06:20)

3. Dual-Process vs. Continuous Models (08:00–10:30)

• The dual-process model posits two separate, dichotomous systems.
• Krigolson confides that he personally supports a more continuous model, in which there’s a dynamic interplay and monitoring between the systems.
• For the scope of this episode, he explains the tradition System One/Two dichotomy for clarity.

4. System One vs. System Two: Practical Examples (10:30–13:30)

• System One (fast, automatic):
  • Simple math: "What’s two plus two?” – Immediate: "Four." (11:05)
  • Completing common phrases: "Bread and…" – "Butter." (11:20)
  • Instinctive perceptual judgments: visual size comparisons.
• System Two (slow, effortful):
  • Complex math: "13,678 divided by 13."
  • Uncommon facts: "What is the second highest mountain in the world?" (Note: Krigolson guesses “K2.”)
  • Chess: Quick moves by experts can be System One, but unfamiliar or complex scenarios demand System Two.

“If I say something like 13,678 divided by 13, most of us can’t rip that off as a System one decision. So we call that System two.” (11:50)

5. Context & Brain Areas Associated with Each System (13:30–16:00)

• System One: Associated with midbrain structures, operates with minimal cortical input.
• System Two: Centered on the prefrontal cortex, which manages analytic and controlled thought.
• Recommendation: "Go to Google images and type in prefrontal cortex." (15:10)

6. Further Distinctions Between the Systems (16:00–19:30)

• Types of Processing:
  • System One: Automatic, implicit, associative.
  • System Two: Controlled, explicit, rule-based.
• Characteristics:
  • System One: Fast, potentially error-prone (“erroneous”).
  • System Two: Slow, effortful, typically more accurate.
• Working memory:
  • System One: Doesn’t require working memory.
  • System Two: Requires retrieval and use of working memory.
• Nice Kahneman-inspired distinction:
  • “System one is basically things that happen to you, and system two is things that you do.” (18:35)

7. Applying Fast/Slow Decisions in Everyday Life (19:30–23:00)

• System One decisions are often stimulus-response, without full assessment of value:
  Example: Stopping at a red light—“You put your foot down. System one decision, you’re not assessing value.” (20:10)
• System Two kicks in with ambiguity or risk:
  • Example: Driving on ice and having to deliberate on the best course of action.
• The Explore/Exploit Dilemma links closely with System Two—when choosing to assess more options rather than picking the apparent best.

8. Having Similar Contexts but Different Systems (23:00–25:20)

• The same context can activate either system depending on familiarity, experience, and risk.
• System Two becomes more relevant when faced with uncertainty or when values of options are similar.
• If there’s an obvious best choice, it tends to trigger System One.
• Krigolson reiterates that even in fast choices, the prefrontal cortex might always be monitoring, ready to recruit more cognitive resources if needed, supporting his continuous model.

“It’s far more likely that the prefrontal cortex is always keeping an eye on the situation, kind of like a, you know... the hound dog who’s lying there and opens one eye every once in a while to see what’s going on.” (25:00)

Notable Quotes and Memorable Moments

• On podcast growth and purpose:

  “And here we are a couple years later… and we have over a million downloads. And I just want to say thank you so much… I love telling you about neuroscience, and especially the neuroscience of daily life.” (01:05)

• On System One/Two:

  “System one is your gut hunch system where you make these very sort of rapid gut hunch responses. And system two is a more analytical system where you, you make a more rational thought out choice.” (06:20)

• On personal learning:

  “The second highest mountain in the world… I want to say K2, but I don’t think that’s correct.” (12:20)

• On context-sensitive decision-making:

  “It’s important to realize that you can have a similar context, and sometimes it’s system one and sometimes it’s System two. It really, really depends on the context, like I said.” (14:30)

• On continuous oversight in decision-making:

  “I think it’s far more likely that the prefrontal cortex is always keeping an eye on the situation, kind of like a … hound dog…” (25:00)

Important Segment Timestamps

• Recap of Decision Model: 02:00–05:30
• System One vs. System Two Intro: 05:30–08:00
• System Examples: 10:30–13:30
• Brain Areas Linked: 13:30–16:00
• Processing Differences: 16:00–19:30
• Everyday Examples: 19:30–23:00
• Continuous Model Explanation: 24:00–26:00

Episode Takeaways

• Decision-making involves multiple stages and is not simply about choosing the highest value option.
• The “System One/System Two” model captures the difference between fast, intuitive decisions and slow, deliberative ones—but the reality may be more nuanced, with systems operating along a continuum.
• Brain regions differ between systems: midbrain for System One, prefrontal cortex for System Two.
• Examples and insights illuminate how these systems work in roles ranging from trivia recall to dangerous driving scenarios.
• Look forward to a deeper dive into neuroanatomy in the next episode.

This summary captures the flow, content, and spirit of the episode, providing a clear and comprehensive guide for listeners new and old.