Threshold model

Classic threshold models were introduced by Sakoda,[2] in his 1949 dissertation and the Journal of Mathematical Sociology (JMS vol 1 #1, 1971).

Schelling demonstrated that “there is no simple correspondence of individual incentive to collective results,” and that the dynamics of movement influenced patterns of segregation.

Edward J. Calabrese and Linda A. Baldwin wrote: An alternative type of model in toxicology is the linear no-threshold model (LNT), while hormesis correspond to the existence of opposite effects at low vs. high dose, which usually gives a U- or inverted U-shaped dose response curve.

Because the threshold is defined relative to the population & environment, the liability score is generally considered as a N(0, 1) normally distributed random variable.

Continuous traits like height or intelligence could be modeled as normal distributions, influenced by a large number of genes, and the heritability and effects of selection easily analyzed.

The first threshold models in genetics were introduced by Sewall Wright, examining the propensity of guinea pig strains to have an extra hind toe, a phenomenon which could not be explained as a dominant or recessive gene, or continuous "blinding inheritance".

[7][8] The modern liability-threshold model was introduced into human research by geneticist Douglas Scott Falconer in his textbook[9] and two papers.