Comments on "Comparing the productive vocabularies of Grey parrots (Psittacus erithacus) and young children".

Roubalová et al. (Anim Cogn 27(45), 2024) have written an intriguing paper in which they compare the acquired human speech patterns of Grey parrots (Psittacus erithacus) raised as companion animals to those of typically developing human toddlers (Homo sapiens) predominantly raised by stay-at-home mothers; birds and humans were ostensibly matched for vocabulary size. The authors' data collection and analyses are impressive and I applaud their efforts; however, I take exception to their assumptions, as they clearly state in their Introduction, that children and parrots received comparable input and their conclusions, also clearly stated, that the differences observed in initial output were a consequence primarily of human uniqueness-i.e., as they argue, "the sociocognitive specifics of the human language." Contrary to the authors' claims, the input received by the parrots was very likely quite impoverished when compared to that of the children. Moreover, the birds were acquiring a heterospecific communication code from heterospecific models whereas the children were learning a conspecific code from conspecifics; the birds' experiences were therefore somewhat more like that of humans learning a second language without explicit instruction. Thus, the conclusions drawn from the authors' meticulous research should be on how much communicative behavior parrots can acquire despite receiving input of inadequate quality and quantity, rather than on direct comparisons with human toddlers receiving optimal input.