According to Greenberg, basic relationships can be determined without any experience in the case of languages that are fairly closely related, though knowledge of probable paths of sound change acquired through typology allows one to go farther faster.
Thus, according to Greenberg (2005:318), phonological considerations come into play from the very beginning, even though mass comparison does not attempt to produce reconstructions of protolanguages as these belong to a later phase of study.
Earlier in his career, before he fully developed mass comparison, he even stated that his methodology did not "conflict in any fashion with the traditional comparative method" (1957:44).
[3] Reflecting the methodological empiricism also present in his typological work, he viewed facts as of greater weight than their interpretations, stating (1957:45): The presence of frequent errors in Greenberg's data has been pointed out by linguists such as Lyle Campbell and Alexander Vovin, who see it as fatally undermining Greenberg's attempt to demonstrate the reliability of mass comparison.
Greenberg's data also contains errors of a more systematic sort: for instance, he groups unrelated languages together based on outdated classifications or because they have similar names.
[7][9] Greenberg has responded to this criticism by claiming that "the method of multilateral comparison is so powerful that it will give reliable results even with the poorest data.
[9] A prominent criticism of mass comparison is that it cannot distinguish borrowed forms from inherited ones, unlike comparative reconstruction, which is able to do so through regular sound correspondences.
For instance, in the words of Campbell, Finnish has borrowed "from its Baltic and Germanic neighbors various terms for basic kinship and body parts, including 'mother', 'daughter', 'sister', 'tooth', 'navel', 'neck', 'thigh', and 'fur'".
Greenberg is correct in pointing out that borrowing of pronouns or morphology is rare, but it cannot be ruled out without recourse to a method more sophisticated than mass comparison.
[9] Though they are less susceptible to borrowing, pronouns and morphology also typically display a restricted subset of a language's phonemic inventory, making cross-linguistic chance resemblances more likely.
[9] Proponents of mass comparison often neglect to exclude classes of words that are usually considered to be unreliable for proving linguistic relationships.
Finally, "nursery words", such as "mama" and "papa" lack evidential value in linguistic comparison, as they are usually thought to derive from the sounds infants make when beginning to acquire languages.
[3][7] The fact that many of indigenous languages of the Americas have pronouns that begin with nasal stops, which Greenberg sees as evidence of common ancestry, may ultimately also be linked to early speech development; Algonquian specialist Ives Goddard notes that "A gesture equivalent to that used to articulate the sound n is the single most important voluntary muscular activity of a nursing infant".
Since those systematic correspondences are extremely unlikely to be random coincidences, the most likely explanation by far is that the two languages have evolved from a single ancestral tongue (Latin, in this case).
[14] The Neogrammarians did not, however, regard regular sound correspondences or comparative reconstructions as relevant to the proof of genetic relationship between languages.
Finally, the supposition that all of the language families generally accepted by linguists today have been established by the comparative method is untrue.
Furthermore, other specific problems affect "comparative" lists of both proposals, like the late attestation for Altaic languages, or the comparison of not certain proto-forms.
If mass comparison differs from it in any obvious way, it would seem to be in the theoretization of an approach that had previously been applied in a relatively ad hoc manner and in the following additions: The positions of Greenberg and his critics therefore appear to provide a starkly contrasted alternative: Besides systematic changes, languages are also subject to random mutations (such as borrowings from other languages, irregular inflections, compounding, and abbreviation) that affect one word at a time, or small subsets of words.
As those sporadic changes accumulate, they will increasingly obscure the systematic ones—just as enough dirt and scratches on a photograph will eventually make the face unrecognisable.
Edward Vajda, noted for his recent proposal of Dené–Yeniseian, attempts to stake out a position that is sympathetic to both Greenberg's approach and that of its critics, such as Lyle Campbell and Johanna Nichols.