Steven Byrnes

Model

I’m not sure if this is what you’re looking for, but here’s a fun little thing that came up recently I was when writing this post:

Summary: “Thinking really hard for five seconds” probably involves less primary metabolic energy expenditure than scratching your nose. (Some people might find this obvious, but other people are under a mistaken impression that getting mentally tired and getting physically tired are both part of the same energy-preservation drive. My belief, see here, is that the latter comes from an “innate drive to minimize voluntary motor control”, the former from an unrelated but parallel “innate drive to minimize voluntary attention control”.)

Model: The net extra primary metabolic energy expenditure required to think really hard for five seconds, compared to daydreaming for five seconds, may well be zero. For an upper bound, Raichle & Gusnard 2002 says “These changes are very small relative to the ongoing hemodynamic and metabolic activity of the brain. Attempts to measure whole brain changes in blood flow and metabolism during intense mental activity have failed to demonstrate any change. This finding is not entirely surprising considering both the accuracy of the methods and the small size of the observed changes. For example, local changes in blood flow measured with PET during most cognitive tasks are often 5% or less.” So it seems fair to assume it’s <<5% of the ≈20 W total, which gives <<1 W × 5 s = 5 J. Next, for comparison, what is the primary metabolic energy expenditure from scratching your nose? Well, for one thing, you need to lift your arm, which gives mgh ≈ 0.2 kg × 9.8 m/s² × 0.4 m ≈ 0.8 J of mechanical work. Divide by maybe 25% muscle efficiency to get 3.2 J. Plus more for holding your arm up, moving your finger, etc., so the total is almost definitely higher than the “thinking really hard”, which again is probably very much less than 5 J.

Technique: As it happened, I asked Claude to do the first-pass scratching-your-nose calculation. It did a great job!

Evaluation Results

6.5
Final Score
Surprise
7.0/10

Run 1:

I would rate this model as a 7 out of 10 on the surprising scale for members of the rationalist and effective altruism communities. Here's my reasoning:

  1. Contradiction of Expectations: The finding that intense mental effort requires less metabolic energy than a simple physical action like scratching one's nose contradicts common intuitions about mental exertion. Many people, even in these communities, might assume that challenging cognitive tasks are metabolically costly.

  2. Counterintuitiveness: The idea that the brain's energy consumption doesn't significantly increase during intense mental activity is non-obvious. It challenges the common perception that mental fatigue is directly related to energy expenditure.

  3. Discovery of Unknowns: While not entirely new information, this model highlights an often overlooked aspect of brain function - its relatively constant energy consumption regardless of mental activity. This could lead to new insights about the nature of mental fatigue and cognitive effort.

  4. Magnitude of Difference: The difference between the energy expended in intense thinking (<<5 J) and a simple physical action like scratching one's nose (>3.2 J) is significant and unexpected.

Specific details that illustrate the surprising aspects:

  1. The fact that whole brain changes in blood flow and metabolism during intense mental activity are undetectable is counterintuitive and challenges common assumptions.

  2. The separation of mental fatigue from physical fatigue into two distinct mechanisms ("innate drive to minimize voluntary attention control" vs. "innate drive to minimize voluntary motor control") provides a novel framework for understanding cognitive effort.

  3. The quantitative comparison between mental and physical tasks is striking - the idea that scratching one's nose requires more energy than intense thinking for five seconds is likely to be surprising to many.

While these findings might not be entirely new to neuroscientists, they are likely to challenge the intuitions of many in the rationalist and EA communities, hence the relatively high surprise rating of 7/10. The model provides a quantitative basis for understanding the energy costs of cognition, which could have implications for discussions about AI, consciousness, and cognitive enhancement within these communities.


Run 2:

To evaluate the surprisingness of this Fermi model, I'll consider the key aspects you outlined:

  1. Contradiction of Expectations: This model challenges a common intuition that intense mental effort is energetically costly. Many people assume that mental fatigue is directly related to energy expenditure, similar to physical fatigue.

  2. Counterintuitiveness: The finding that scratching one's nose likely requires more energy than intense thinking for 5 seconds is non-obvious and reveals a hidden complexity in how we perceive mental vs. physical effort.

  3. Discovery of Unknowns: While not entirely new information to neuroscientists, this model uncovers a generally unrecognized fact about the minimal energy costs of cognitive effort for the broader rationalist and EA communities.

  4. Magnitude of Difference: The difference between the energy expenditure of intense thinking (<5 J) and a simple physical action like scratching one's nose (>3.2 J) is significant enough to be noteworthy, though not extreme.

Specific surprising aspects:

  1. The negligible change in whole-brain energy consumption during intense mental activity.
  2. The comparison between mental and physical tasks, showing that a seemingly trivial physical action can require more energy than intense thinking.
  3. The implication that mental fatigue is not primarily driven by energy conservation, but by other mechanisms (like the "innate drive to minimize voluntary attention control").

Rating: 7/10

This rating reflects that while the information isn't entirely novel in neuroscience, it's likely to be quite surprising to many in the rationalist and EA communities. The counterintuitive nature of the finding and its contradiction of common assumptions about mental effort make it notably surprising. However, it doesn't completely overturn major theories or reveal entirely unknown phenomena, which prevents it from scoring higher on the surprise scale.


Run 3:

I would rate this model and its findings as a 7 out of 10 on the surprising scale for members of the rationalist and effective altruism communities. Here's my reasoning:

  1. Contradiction of Expectations: The model challenges a common intuition that intense mental effort is energetically costly. Many people, even in rationalist circles, might assume that "thinking really hard" consumes significant energy, comparable to physical tasks. This finding contradicts that assumption.

  2. Counterintuitiveness: The idea that scratching one's nose requires more energy than intense thought is non-obvious and reveals hidden complexities about brain function and energy expenditure.

  3. Discovery of Unknowns: While not entirely new information, this model helps uncover and quantify the surprisingly low energy cost of mental effort, which might not have been widely recognized or appreciated within these communities.

  4. Magnitude of Difference: The difference between the energy expenditure of intense thought (<<5 J) and a simple physical action like scratching one's nose (>3.2 J) is significant and likely larger than most would expect.

Specific aspects that contribute to the surprising nature of the findings:

  1. The model suggests that the net extra primary metabolic energy expenditure for intense thinking might be zero, which is counterintuitive.

  2. It highlights that attempts to measure whole brain changes in blood flow and metabolism during intense mental activity have failed to demonstrate any change, which challenges common assumptions about brain energy use.

  3. The comparison to a simple physical action (scratching one's nose) provides a tangible and relatable reference point that emphasizes how little energy intense thinking actually requires.

  4. The model supports the idea that mental fatigue is not directly related to energy expenditure, but rather to an "innate drive to minimize voluntary attention control," which is a nuanced perspective that many might not have considered.

While this information might not be entirely new to some experts in neuroscience or cognitive science, it's likely to be surprising and thought-provoking for many in the rationalist and EA communities. The quantification and clear comparison make the concept more concrete and impactful.

A rating of 7 reflects that while this information is quite surprising and counterintuitive, it's not completely revolutionary or paradigm-shifting for these communities, who are often exposed to counterintuitive scientific findings.

Topic Relevance
5.3/10

Run 1:

To evaluate the importance of this Fermi model to the rationalist and effective altruism communities, I'll consider its relevance and potential impact:

Relevance: 6/10 The model addresses a misconception about mental and physical energy expenditure, which is tangentially related to rationalist interests in cognitive science and understanding how the mind works. It challenges intuitive beliefs about thinking and energy use, which aligns with rationalist goals of overcoming cognitive biases. However, it's not directly addressing core rationalist or EA topics like decision-making, existential risk, or altruism.

Impact Potential: 4/10 While interesting, the model's findings are unlikely to significantly influence decision-making or priority-setting within these communities. It may spark some discussion about cognitive processes and energy use, but it doesn't have clear actionable implications for rationalist or EA goals. The impact is likely to be limited to adjusting some misconceptions about mental effort.

Overall Score: 5/10 This score represents the median expectation. The model is interesting and relevant to rationalist interests in understanding cognition, but its impact on core community goals and priorities is limited. It's a good example of applying rational thinking and quantitative analysis to challenge intuitions, which is valuable to the community, but not groundbreaking in terms of its implications or applications.


Run 2:

To evaluate the importance of this Fermi model to the rationalist and effective altruism communities, I'll consider its relevance and potential impact:

Relevance: 6/10 The model addresses a misconception about mental effort and energy expenditure, which is tangentially related to topics of interest in rationalist circles like cognitive biases, decision-making, and understanding the mind. It challenges intuitive beliefs about thinking and energy use, which aligns with rationalist goals of improving reasoning and questioning assumptions. However, it's not directly addressing core EA or rationalist priorities.

Impact Potential: 4/10 While interesting, the model's findings are unlikely to significantly influence decision-making or priority-setting within these communities. It may slightly inform discussions on mental fatigue or productivity, but its practical applications seem limited. The impact is more likely to be in shifting some individual perspectives rather than driving community-wide changes.

Overall Score: 5/10 This score represents the median expectation. The model is moderately relevant and somewhat interesting to the rationalist community, but its direct importance and potential for impact are limited. It's a neat exploration that challenges some assumptions, but doesn't address core priorities or have major implications for EA or rationalist goals.


Run 3:

I would rate this model a 6 out of 10 for importance to the rationalist and effective altruism communities. Here's my reasoning:

Relevance (moderate to high):

  • The model addresses misconceptions about mental effort and energy expenditure, which is relevant to discussions of cognitive biases, decision-making, and productivity - all topics of interest in rationalist circles.
  • It challenges intuitive beliefs about the nature of mental exertion, encouraging a more evidence-based understanding of cognition.

Impact Potential (moderate):

  • While not directly addressing major EA cause areas or rationalist priorities, this model could influence how people think about mental effort and cognitive resource allocation.
  • It may lead to refined approaches to productivity, task management, and cognitive enhancement within these communities.
  • The model might spark further research or discussion on the nature of mental fatigue and its implications for rationality and effective decision-making.

Reasons for not rating higher:

  • The model, while interesting, does not directly address core EA priorities like existential risk, global poverty, or animal welfare.
  • Its immediate practical applications for improving rationality or altruistic impact are not immediately clear.

Reasons for rating above median:

  • The model exemplifies the kind of counterintuitive, quantitative reasoning valued in rationalist circles.
  • It challenges common intuitions, potentially leading to improved mental models of cognition and effort.
  • The approach demonstrates good use of scientific literature and Fermi estimation techniques.

Overall, while not revolutionary, this model provides a thought-provoking example of applying rationalist thinking to everyday assumptions, making it moderately important to these communities.

Robustness
6.3/10

Run 1:

Evaluation of the Fermi model:

Score: 7/10

Justification:

This Fermi model is relatively robust, considering the factors you've outlined. Here's a detailed breakdown:

  1. Sensitivity to Assumptions: The model makes conservative assumptions and uses upper bounds, which reduces sensitivity to specific parameter choices. For example, it assumes <<5% energy change for intense mental activity, which is likely an overestimate. This approach provides a margin of error that strengthens the conclusion.

  2. Evidence Base: The model cites a peer-reviewed scientific paper (Raichle & Gusnard 2002) for its key data point on brain energy expenditure during mental activity. This lends credibility to the core assumption. However, the model could be strengthened by including more recent studies to confirm that this finding still holds.

  3. Methodological Rigor: The model uses sound reasoning and appropriate methods for a Fermi estimation. It breaks down the problem into comparable units (Joules) and uses basic physics principles (e.g., mgh for potential energy) to estimate physical movement energy. The comparison between mental and physical activity is logical and well-structured.

  4. Consensus of Assumptions: The underlying assumptions are likely to be well-accepted within the rationalist and EA communities. The idea that mental fatigue is distinct from physical fatigue aligns with current understanding in cognitive science and neurobiology.

Strengths:

  • Conservative estimates and upper bounds
  • Use of peer-reviewed scientific literature
  • Clear, step-by-step reasoning
  • Comparison of mental and physical activities in the same units

Weaknesses:

  • Reliance on a single, somewhat dated study for brain energy expenditure
  • Some simplifications in the physical movement calculations (e.g., not accounting for all muscle movements in nose-scratching)

The model scores above average (7/10) due to its methodological soundness, conservative approach, and grounding in scientific literature. However, it falls short of a higher score due to the reliance on a single study and some simplifications in the physical calculations. Nonetheless, the conclusion is likely robust to reasonable changes in assumptions, making it a solid Fermi estimation.


Run 2:

Thank you for sharing this interesting Fermi model comparing the energy expenditure of intense thinking versus scratching one's nose. I'll evaluate its robustness based on the criteria you outlined.

Robustness Score: 6/10

Justification:

  1. Sensitivity to Assumptions: The model relies on several assumptions, but most are reasonably conservative. The key assumption of <<5% energy increase for intense thinking is based on published research, which adds credibility. The mechanical work calculation for lifting an arm is straightforward and based on basic physics. The 25% muscle efficiency is a reasonable estimate, though it could vary. Overall, the model's conclusions seem robust to small changes in these assumptions.

  2. Evidence Base: The model cites a reputable scientific paper (Raichle & Gusnard 2002) for its core assumption about brain energy use. This strengthens the evidence base considerably. However, the model would be more robust if it included additional sources to corroborate these findings or to support other assumptions (e.g., muscle efficiency).

  3. Methodological Rigor: The approach is logical and uses appropriate physical principles. The author acknowledges uncertainties and uses conservative estimates, which is good practice. The comparison between mental and physical tasks is creative and insightful. However, the model could be improved by more explicitly stating all assumptions and providing sensitivity analysis for key parameters.

  4. Consensus of Assumptions: The underlying assumptions about brain energy use and basic physics are likely to be widely accepted in rationalist and EA communities. The idea that mental fatigue is not directly related to energy expenditure might be more controversial, but the author provides a link to a more detailed explanation of this concept.

Strengths:

  • Uses published scientific research for key assumptions
  • Employs basic physics principles correctly
  • Acknowledges uncertainties and uses conservative estimates
  • Provides an insightful comparison between mental and physical tasks

Weaknesses:

  • Relies on a single source for brain energy use data
  • Could benefit from more explicit statement of all assumptions
  • Lacks sensitivity analysis for key parameters
  • The conclusion about mental fatigue mechanisms is not fully explored in this model

In conclusion, while this model has some limitations, it provides a reasonable first-pass estimate and insight into the relative energy costs of mental versus physical tasks. Its use of published research and conservative estimates lends credibility to its conclusions. However, additional sources and more detailed sensitivity analysis would further increase its robustness. The score of 6/10 reflects a model that is above average in robustness but with room for improvement.


Run 3:

I'll evaluate this Fermi model based on the criteria provided:

Robustness Score: 6/10

Justification:

  1. Sensitivity to Assumptions: The model relies on several assumptions, but most are reasonably conservative. The upper bound of 5% change in blood flow for intense mental activity is based on published research, which is a strength. The assumption that thinking hard is <<5% of total brain energy use seems reasonable but could be challenged. The physical calculations for scratching one's nose are based on basic physics principles, which are robust. However, the 25% muscle efficiency is an estimate that could vary.

  2. Evidence Base: The model cites a credible scientific paper (Raichle & Gusnard 2002) for its key assumption about brain energy use. This strengthens the model's foundation. However, more recent studies could potentially provide updated or more precise figures. The physical calculations are based on well-established principles.

  3. Methodological Rigor: The approach is logical, comparing mental and physical energy expenditure. The author acknowledges uncertainties and uses conservative estimates (e.g., "<<5%"), which is good practice. The comparison method is appropriate for a Fermi estimation. However, the model could benefit from more explicit consideration of error margins.

  4. Consensus of Assumptions: The basic premise that mental effort doesn't significantly increase overall brain energy use is likely to be accepted in rationalist circles, based on the cited research. The physical calculations are based on widely accepted principles. The distinction between mental and physical tiredness as separate mechanisms might be more controversial but is not central to the energy calculation.

Strengths:

  • Use of published scientific research for key assumptions
  • Conservative estimates and acknowledgment of uncertainties
  • Logical comparison method
  • Grounding in basic physical principles for the comparative calculation

Weaknesses:

  • Some assumptions could benefit from more recent or comprehensive data
  • Lack of explicit error analysis
  • The 25% muscle efficiency figure could be better sourced or justified

Overall, this model presents a reasonable Fermi estimation that aligns with scientific understanding. It's not highly precise but provides a useful order-of-magnitude comparison. The approach is sound, and the key conclusion is likely robust to moderate changes in assumptions. The score of 6/10 reflects a model that is above average in robustness but leaves room for refinement and more comprehensive data support.

Model Quality
6.7/10

Run 1:

Thank you for providing this Fermi model for evaluation. I'll assess it based on the criteria you've outlined and provide a numeric score along with my observations.

Score: 7/10

Observations:

  1. Comprehensiveness: The model addresses the key factors relevant to comparing the energy expenditure of intense thinking versus a simple physical action. It considers both mental and physical aspects, which is appropriate for the comparison. However, it could be more comprehensive by including factors such as individual variations or different types of mental tasks.

  2. Data Integration: The model integrates data from a reputable scientific source (Raichle & Gusnard 2002), which adds credibility. The use of established data for brain energy consumption is a strength. However, more diverse sources could have been used to cross-validate the findings.

  3. Clarity of Assumptions: The assumptions are generally clear and reasonable. The model distinguishes between empirical data (from the cited study) and estimates (like muscle efficiency). The assumption that thinking hard is <<5% of total brain energy is justified based on the cited study.

  4. Transparency and Replicability: The model is relatively transparent, with clear steps in the calculation process. Others could likely replicate the results. However, more detailed documentation of each step would improve replicability.

  5. Logical Consistency: The model follows a logical structure, starting with brain energy expenditure and then comparing it to the physical action of scratching one's nose. The reasoning is coherent and leads to a sensible conclusion.

  6. Communication: The findings are communicated clearly, with a good summary at the beginning. The use of calculations and comparisons enhances understanding. However, visual aids like charts or graphs could have further improved the presentation.

  7. Practical Relevance: The model provides an interesting insight that challenges common misconceptions about mental versus physical energy expenditure. While not immediately actionable, it could influence how people think about mental effort and energy management.

Strengths:

  • Clear and concise presentation
  • Use of scientific data to support arguments
  • Logical comparison between mental and physical tasks
  • Challenges common misconceptions effectively

Areas for Improvement:

  • Could include more diverse data sources
  • Visual aids would enhance communication
  • More detailed documentation of calculation steps
  • Consideration of individual variations or different types of mental tasks

Overall, this is a well-constructed Fermi model that effectively addresses its intended question. It's above average in quality, hence the score of 7/10. The model's strengths in logical consistency, data integration, and clear communication outweigh its minor shortcomings in comprehensiveness and visual presentation.


Run 2:

Thank you for providing this Fermi model submission. I'll evaluate it based on the criteria you've outlined and provide a numeric score along with my observations.

Score: 7/10

Observations:

  1. Comprehensiveness: The model addresses the key factors relevant to comparing the energy expenditure of intense thinking vs. a simple physical action. It considers both mental and physical energy expenditure, which is crucial for this comparison. However, it could be more comprehensive by including factors such as individual variations or different types of mental tasks.

  2. Data Integration: The model integrates data from a reputable scientific source (Raichle & Gusnard 2002), which adds credibility. However, it relies heavily on this single source for mental energy expenditure, and more diverse sources could strengthen the model.

  3. Clarity of Assumptions: The assumptions are generally clear and reasonable. The model explicitly states when it's making approximations (e.g., "it seems fair to assume it's <<5% of the ≈20 W total"). It also distinguishes between empirical data and speculative inputs.

  4. Transparency and Replicability: The model's process is transparent, with clear steps and calculations. Others could easily replicate or audit the results. The use of formulas (e.g., mgh for potential energy) enhances replicability.

  5. Logical Consistency: The model follows a logical structure, starting with mental energy expenditure, then comparing it to physical energy expenditure. The reasoning is coherent and leads logically from premises to conclusions.

  6. Communication: The findings are clearly communicated, with a concise summary at the beginning. However, the model could benefit from visual aids like charts or graphs to enhance understanding, especially for comparing the energy expenditures.

  7. Practical Relevance: The model provides an interesting insight that challenges common misconceptions about mental vs. physical energy expenditure. While not immediately actionable, it could inform discussions about cognitive effort and energy management.

Strengths:

  • Clear and logical structure
  • Use of scientific data to support assumptions
  • Transparent calculations that can be easily followed
  • Challenges common misconceptions with quantitative reasoning

Areas for Improvement:

  • Could include more diverse data sources
  • Visual aids would enhance communication
  • More exploration of practical implications or applications

Overall, this is a well-constructed Fermi model that effectively addresses its primary question. It's above average in quality, hence the score of 7/10. The model's strengths in logical consistency, transparency, and challenging assumptions are particularly noteworthy.


Run 3:

Thank you for providing this Fermi model for evaluation. I'll assess the model based on the criteria you've outlined and provide a numeric score along with my observations.

Score: 6/10

Justification:

  1. Comprehensiveness (6/10): The model addresses the key factors relevant to comparing the energy expenditure of intense thinking versus a simple physical action. It considers brain metabolism, physical movement, and muscle efficiency. However, it could be more comprehensive by including factors such as individual variations, different types of cognitive tasks, or the potential for increased overall metabolic rate during intense thinking.

  2. Data Integration (7/10): The model integrates data from a reputable scientific source (Raichle & Gusnard 2002) for brain metabolism. The physical calculations for scratching one's nose are based on basic physics principles. The data usage is appropriate, though more recent or diverse sources could enhance the model's robustness.

  3. Clarity of Assumptions (6/10): The model clearly states some assumptions, such as the upper bound for brain energy change and muscle efficiency. However, it could be more explicit about other assumptions, like the height of arm movement or the duration of nose scratching.

  4. Transparency and Replicability (7/10): The model's process is generally transparent, with calculations shown for both the thinking and physical action components. Others could likely replicate the results, though more detailed step-by-step explanations would improve replicability.

  5. Logical Consistency (8/10): The model follows a logical structure, comparing the energy expenditure of thinking to a physical action in a coherent manner. The reasoning from premises to conclusions is clear and consistent.

  6. Communication (5/10): While the model effectively communicates its findings, it lacks visual aids or summary tools that could enhance understanding. The presentation is text-heavy and could benefit from a more structured format or graphical representations.

  7. Practical Relevance (5/10): The model provides an interesting insight into the relative energy costs of mental and physical activities. However, its practical applications or actionable recommendations are limited. It serves more as an interesting factoid than a basis for decision-making.

Additional Observations:

  • The model's strength lies in its novel comparison between mental and physical energy expenditure, challenging common misconceptions.
  • The use of an AI assistant (Claude) for initial calculations is an interesting approach, though it would be beneficial to verify these calculations independently.
  • The model could be improved by considering a wider range of cognitive tasks and physical actions for comparison.

In conclusion, this Fermi model presents an intriguing comparison with some solid foundational elements. Its main strengths are in logical consistency and data integration, while areas for improvement include comprehensiveness, communication, and practical relevance. The score of 6/10 reflects a model that is above average in quality but with room for enhancement in several areas.