Personality and Individual Differences
Set the truth, generate fictional twin pairs, estimate it back — and then break the assumptions one at a time and watch the estimates go wrong in specific directions.
Simulated — fictional pairs from a seeded generator, no real study
By the end you should be able to say what heritability is a property of, and which way each assumption pushes the estimate when it fails.
About 30 minutes. Nothing you do here is saved or sent anywhere.
Heritability is the proportion of variance in a population attributable to genetic variance in that population under those environmental conditions. It is not the proportion of any individual's trait caused by their genes, and it says nothing about whether a trait can be changed.
A study reports that a trait has a heritability of 0.50.
You set the true variance components. The simulator generates 250 pairs in each group from them, and Falconer's formulae estimate them back from the correlations. Real studies only ever see the right-hand column.
250 pairs per group, generated from a seed. No real family, study or dataset is involved.
| Group | Pairs | Correlation |
|---|
| Component | Truth | Estimated | Error |
|---|
A heritability estimate is a ratio, and a ratio has a denominator: it describes how much of the variation in this population, as sampled, on this measure tracks genetic variation. Change the range of environments and the same genes give a different figure. It is not a statement about any individual, and a high value does not mean a trait is fixed.