[pikma]

If thinking hard required a lot of energy, wouldn't we expect that thinking hard would cause an increased heart rate and faster breathing?

[yieldcrv]

the brain has enough blood and oxygen, it uses that to depletes other resources when firing

so no.

think of it like a computer, drawing more electricity faster won’t help the physical properties of the RAM or transport bus (much). it already has enough of that, the bottleneck is elsewhere. but good breathing does help cognition

compared to muscles the brain is a small surface area with a wide bus. when exercising, the demands are about getting more oxygen to more muscles, which is merely transported by blood, and the heart beats faster to pump blood faster, the breathing is an attempt to oxygenate more blood. thats the difference between muscular activity and brain activity