Decision making with complex nonlinear systems: inference and identification in the context of DS22q11.2

A rare gene deletion syndrome, that has in its associated phenome some possible cognitive and psychotic features, has been examined with DNA and fMRI for its causal basis within families and its statistical distribution in populations. Identification of its presence without DNA evidence is problematic as the condition is not stationary nor linear in its properties as the carrier grows older. Within a family its distribution is Mendelian, but there are also complications due to its complexity. A combined approach using both signal detection and an extension of Bayes theorem is a possible approach to discriminating between symptoms that have potentially a multi-causal basis, of which 22q11.2 deletion is only one possibility. Two later issues have arisen, one involving possibly at least two genetically different syndromes that result in similar autism in infancy, the other in statistical problems of prediction. Diagnosis of probable early DS 22q11.2 independent deaths as opposed to survival into adulthood can be wrongly thought to be a case of infanticide, and legal disputes have consequently arisen in the U.K., the USA, and Australia.