Question 1

Do we really only use 10% of our brain?

Accepted Answer

No. It is one of the most thoroughly disproved claims in popular science, and **essentially every line of evidence contradicts it**.

**What the evidence shows:**

**Imaging.** Functional MRI and PET scans show activity throughout the brain across a day. No large region sits permanently idle, and even during sleep most of the brain is active.

**Damage.** If 90% were spare, damage to most of the brain would be harmless. It is not — **small strokes or injuries in almost any region produce identifiable deficits**, which is precisely how neurologists localise damage.

**Energy.** The brain is about 2% of body mass and consumes roughly 20% of the body's energy at rest. Evolution does not fund idle tissue at that price.

**Structure.** Unused neural tissue degenerates. Pathways that lose their input shrink and get reallocated, as seen in the visual cortex of people blind from birth.

**Electrical mapping.** Direct stimulation during neurosurgery produces responses across the cortex, with no vast silent zones.

**Where the myth came from.** Several sources, none good. William James wrote that people meet only a fraction of their mental potential — a claim about **achievement, not anatomy**. Early researchers found large areas whose function they could not identify and called them "silent" cortex; these are the association areas that do the integrative work. The figure was also widely used in advertising for self-improvement courses.

**What is true in the vicinity.** **Not all neurons fire at once** — that would be a seizure. The brain is metabolically efficient and activates what a task needs. And **neurons are outnumbered by glial cells**, which were long thought merely supportive and are now known to be functionally important.

**Why it persists.** It is flattering, it supports a market in unlocking hidden potential, and it recurs constantly in film. **It is also demotivating in a subtler way**: it frames capability as latent rather than developed through practice, which is the opposite of what the evidence on skill acquisition shows.

Question 2

What is statistical power, and why do underpowered studies mislead?

Accepted Answer

Power is the probability that a study will detect an effect if one genuinely exists. Low power means a real effect is likely to be missed — and, far less intuitively, it also makes the findings that

Question 3

Why do we age?

Accepted Answer

There is no single answer, and the honest position is that ageing is multi-causal — a set of interacting processes rather than one clock running down. Researchers have converged on a list of

Question 4

Why can't we remember being a baby?

Accepted Answer

The phenomenon is called infantile amnesia, and almost everyone has it: most adults have no reliable memories from before about age three, and only patchy ones until around seven. The old explanation

Question 5

Why do we yawn and why is it contagious?

Accepted Answer

Nobody is certain, which is unusual for something so universal. Yawning occurs in almost all vertebrates, appears in human foetuses from around 11 weeks, and has resisted a settled explanation for

Question 6

How does scientific consensus form, and what does it actually mean?

Accepted Answer

Through the accumulation of independent, mutually reinforcing evidence across many researchers and methods, until a position becomes the working assumption of a field — and it is a description of the

Question 7

How does fossilisation actually happen?

Accepted Answer

Rarely, and through several different processes — the important point being that fossilisation requires an unusual sequence of events, which is why the fossil record is a biased sample of past life

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