Your Brain Is Not for Thinking

Your brain runs your body using something like a budget. A financial budget tracks money as it’s earned and spent. The budget for your body tracks resources like water, salt and glucose as you gain and lose them. Each action that spends resources, such as standing up, running, and learning, is like a withdrawal from your account. Actions that replenish your resources, such as eating and sleeping, are like deposits.

The scientific name for body budgeting is allostasis. It means automatically predicting and preparing to meet the body’s needs before they arise. Consider what happens when you’re thirsty and drink a glass of water. The water takes about 20 minutes to reach your bloodstream, but you feel less thirsty within mere seconds. What relieves your thirst so quickly? Your brain does. It has learned from past experience that water is a deposit to your body budget that will hydrate you, so your brain quenches your thirst long before the water has any direct effect on your blood.