computerised statistical hypothesis testing methods have been developed which are related to both the comparative method and lexicostatistics. Character based methods are similar to the former and distanced based methods are similar to the latter (see Quantitative comparative linguistics). The characters used can be morphological or grammatical as well as lexical. Since the mid-1990s these more sophisticated tree- and network-based phylogenetic methods have been used to investigate the relationships between languages and to determine approximate dates for proto-languages. These are considered by many to show promise but are not wholly accepted by traditionalists. However, they are not intended to replace older methods but to supplement them. Such statistical methods cannot be used to derive the features of a proto-language, apart from the fact of the existence of shared items of the compared vocabulary. These approaches have been challenged for their methodological problems, since without a reconstruction or at least a detailed list of phonological correspondences there can be no demonstration that two words in different languages are cognate. Related fields There are other branches of linguistics that involve comparing languages, which are not, however, part of comparative linguistics: Linguistic typology compares languages to classify them by their features. Its ultimate aim is to understand the universals that govern language, and the range of types found in the world's languages in respect of any particular feature (word order or vowel system, for example). Typological similarity does not imply a historical relationship. However, typological arguments can be used in comparative linguistics: one reconstruction may be preferred to another as typologically more plausible. Contact linguistics examines the linguistic results of contact between the speakers of different languages, particularly as evidenced in loan words. An empirical study of loans is by definition historical in focus and therefore forms part of the subject matter of historical linguistics. One of the goals of etymology is to establish which items in a language's vocabulary result from linguistic contact. This is also an important issue both for the comparative method and for the lexical comparison methods, since failure to recognize a loan may distort the findings. Contrastive linguistics compares languages usually with the aim of assisting language learning by identifying important differences between the learner's native and target languages. Contrastive linguistics deals solely with present-day languages. Pseudolinguistic comparisons Comparative linguistics includes the study of the historical relationships of languages using the comparative method to search for regular (i.e.