Models for CST prediction will vary depending on what parameters need to be accounted for when constructing the model. Most parsimonious reconstruction (MPR)
Parsimony is the principle in which one chooses the simplest scientific explanation that fits the evidence. In terms of building phylogenetic trees, the best hypothesis is the one that requires the fewest evolutionary changes. Using parsimony to reconstruct ancestral character states on a phylogenetic tree is a method for testing ecological and evolutionary hypotheses. This method can be used in CST studies to estimate the number of character changes that exist between pathogens in relation to their host. This makes MPR useful for tracking a CST pathogen to its origins. MPR can also be used to the compare traits of host species populations. Traits and behaviours within a population could make them more susceptible to CST. For example, species which migrate regionally are important for spreading viruses through population networks.Despite the success of parsimony reconstructions, research suggests they are often sensitive and can sometimes be prone to bias in complex models. This can cause problems for CST models that have to consider many variables. Alternatives methods, such as maximum likelihood, have been developed as an alternative to parsimony reconstruction. Using genetic markers
Two methods of measuring genetic variation, variable number tandem repeats (VNTRs) and single nucleotide polymorphisms (SNPs), have been very beneficial to the study of bacterial transmission.
Expressive language disorder is a communication disorder in which there are difficulties with verbal and written expression. It is a specific language impairment characterized by an ability to use expressive spoken language that is markedly below the appropriate level for the mental age, but with a language comprehension that is within normal limits. There can be problems with vocabulary, producing complex sentences, and remembering words, and there may or may not be abnormalities in articulation.Careful diagnosis is also important because "atypical language development can be a secondary characteristic of other physical and developmental problems that may first manifest as language problems". Models of language production
Willem Levelt outlined the currently accepted theory of speech production. Words are produced after the concept waiting to be produced is conceptualized, related words are selected, encoded and the sound waves of speech are produced. Association with language networks
There is also a lot of debate about whether specific language impairments, such as expressive language disorder, are caused by deficits in grammar or by a deficit in processing language information. However, an alternative hypothesis to the cause of SLIs has been posited, called the Procedural Deficit Hypothesis. The Procedural Deficit Hypothesis opines that we can explain language impairments due to abnormal development of brain structures that are involved in procedural memory, our memories that remember how to perform different cognitive and motor tasks.