A response comes after its cause
- The idea
- Predict
- See it
- Why
- Check
The idea
“If something is always high when a condition shows up, it must have caused that condition.”
When two things always show up together, you can't see which caused the other. It's easy to blame the one you notice, even if it was only responding.
The short version
The mistake: If something is always high when a condition shows up, it must have caused that condition.
What's actually true: A response follows the condition that sets it off. To find the cause, ask which change came first.
- When blood glucose rises, beta cells in the pancreas sense it and release insulin. That's a response, a change set off by a condition.
- Insulin helps body cells take up glucose, so blood glucose falls back toward its set point. That's negative feedback. It didn't create the high glucose.
- If insulin raised glucose, glucose would trail insulin, like the dashed curve. With any data, find what changed first, then ask if the reversed story fits.
On the exam: Ask what changed first. A cause has to come before its effect.