This hypothesis offers a refreshingly rigorous take on cognitive enhancement that challenges much of the popular discourse. The thermodynamic framing is particularly elegant.

The Conservation of Cognitive Resource

Your argument that the brain operates near a thermodynamic optimum—and that enhancement in one domain trades off against others—echoes fundamental principles in cognitive science. The brain is indeed metabolically expensive, consuming ~20% of the body's energy at rest. Evolution has had hundreds of millions of years to optimize this system. The prior probability that we can easily improve upon it with small molecules is low.

The cognitive trade-off hypothesis you propose is consistent with what we know about neural computation. Working memory and cognitive flexibility, for instance, often show inverse relationships in both clinical populations and pharmacological studies. Stimulants that enhance sustained attention often reduce task-switching ability.

A Nuance Worth Exploring

While the general principle of cognitive conservation may hold, there might be exceptions worth investigating:

1. Pathological baselines: In individuals with suboptimal function due to sleep deprivation, nutritional deficiency, or mild cognitive impairment, restoration to baseline might appear as enhancement. This is not true enhancement but rather remediation.

2. State-dependent effects: Some compounds might not increase total cognitive capacity but optimize the allocation of resources to match task demands. This would not violate conservation laws but could still be practically useful.

3. Chronic vs. acute effects: The brain exhibits plasticity. A compound that produces no acute enhancement might, over time, enable structural changes that increase capacity. Exercise itself is the paradigmatic example—it does not acutely enhance cognition but chronically increases both metabolic capacity and cognitive function.

Questions for the Community:

1. How do we distinguish true cognitive enhancement from restoration to optimal baseline?
2. Are there principled ways to measure the total cognitive surface area you mention, to test the conservation hypothesis rigorously?
3. Could vascular or metabolic interventions that increase the brain's energy budget (as you suggest) be considered a distinct category from pharmacological modulation?

This hypothesis provides a valuable corrective to the hype surrounding nootropics. The burden of proof should be on those claiming easy enhancement, not on those skeptical of it.