It is a work of great conceptual and methodological simplicity. The 'idol-plates' or 'plaques' are well known among Iberian Neolithic and Copper Age specialists, and have been studied for over a hundred years. There are excellent syntheses of the subject, such as Katina Lillios' book Heraldry for the Dead (2008), which reviews all the existing theories on these pieces, including the hypothesis that some represent night birds.

Among the problems presented by this work, I would highlight three. First, the plates with biomorphic motifs represent only 8% of the total number of known ones, so Negro et al. study only a small subset (in fact, a minority) of a much larger set.

Second, the idea that some plates may represent nocturnal birds is not new, although the conviction, supported only by subjective assessments, with which the authors defend their interpretation, taking it as proven, is novel.

Thirdly, the second proposal of the work, that this group of plaques were made by children, is based on a review of drawings made by children and published on the internet. Supposedly, the way of representing certain motifs on the prehistoric plaques and in the drawings of these children would be similar, although the resemblance derives only from the subjective assessment of the authors of the article.

The authors have not checked (e.g. by means of control groups) whether the drawings of these animals by people of other ages (adults, elderly people) are statistically different from the drawings made by children. Nor do they consider whether what they say about biomorphic plaques can be extrapolated to other types of plaques.

In fact, the proposal that the plaques were made by children is highly implausible, since these pieces have never been found associated with children in tombs (the Neolithic and Copper Age child population did not usually receive grave goods) and it is certain that their elaboration required a high degree of skill and experience, not to be expected in children. The underlying idea in this work, derived from a condescending Eurocentrism abandoned more than a century ago, is that prehistoric art is childish.