Michael Bell
8th June 2016

A series of recent experiments has shown that various types of fish and birds are able to distinguish between different individual humans. Classically, this has been supposed to be possible only between the members of more advanced species, and specifically for those that have developed socialization to the point of needing to be able to recognize and characterize particular individuals. A husband recognizes his wife, at least if he does not mistake her for a hat; a dog recognizes its mistress; and even a snake knows its owner. Of course, vision is not the only sensory modality involved: smell is no doubt equally important; and if animals are telepathic, they may also be using techniques to which my wife and I have no access.

As described in the journal Scientific Reports, a team of scientists from Oxford and Queensland Universities found that archerfish were able to learn and recognize faces with a high degree of accuracy, discriminating one face from up to 44 others. This species of tropical fish, known for its ability to spit jets of water to knock down aerial prey, were presented with two images of human faces and trained to choose one of them using their jets. The fish were then presented with the learned face and a series of new faces and were able to correctly choose the face they had initially learned to recognize. They were able to do this task even when more obvious features, such as head shape and colour, were removed from the images.

First author Dr Cait Newport, Marie Curie Research Fellow in the Department of Zoology at Oxford University, said: "The fact that archerfish can learn this task suggests that complicated brains are not necessarily needed to recognize human faces. Humans may have special facial recognition brain structures so that they can process a large number of faces very quickly or under a wide range of viewing conditions."

Separately, as reported in PLOS ONE by Masanori Kohda from the Osaka City University, Japan and colleagues, daffodil cochlid fish attended to digital models with unfamiliar faces longer and from a further distance than to models with familiar faces. This is a group-living species and the results suggest that fish may be able to distinguish individuals accurately using facial color patterns.

In two further experiments, animal behaviour experts from the University of Lincoln in the UK and the University of Vienna worked with pigeons and crows. Their results, published in Avian Biology Research shows that pigeons can reliably discriminate between familiar and unfamiliar humans, and that they use facial features to tell people apart. The experimental group birds were able to recognise and classify the familiar people using only their faces, whereas the birds without prior training failed. In a separate study, published in the journal Animal Cognition, the team investigated the ability of carrion crows to differentiate between the voices and calls of familiar and unfamiliar humans and jackdaws. The crows responded significantly more often to unfamiliar than familiar human voices and, conversely, responded more to familiar than unfamiliar jackdaw calls.

Humans have long been inclined to credit themselves with mental abilities denied to 'lesser' species, although little by little, the differences have been whittled away by successive researchers. There always will be differences, of course, albeit in some cases to the disadvantage of humans, but by now research has demonstrated a remarkable degree of homology between the brains of multiple species, including ourselves. Evolution is very parsimonious.

Many scientists are now somewhat grudgingly coming to accept that we are not quite as exceptional as we like to imagine we are, but one respect in which they lag far behind the truth is in respect of sociality. By all means, it is true that the achievements of our society, some glittering and some noticeably debased, have been erected on the foundations of group living, but there is a disconnect between the admitted role of sociality in human existence and its comparable importance for earlier species, which is highlighted by these results, exemplified by the description, above, of cochlid fish as being 'group living', as if other types of fish behave otherwise. Did you ever see a type of fish that did not school? or a type of bird that did not flock? Why then would they not be able to recognize each other, not just as conspecifics, but as individuals? It must be admitted that individuality has reached a peak of elaboration in human groups, but this has been built on a principle that already existed.

In searching for the origins of individuality, we may not go as far as to propose that ragworms distinguish themselves one from another, although even a ragworm may 'notice' or respond to the fact that a fellow ragworm is bigger or smaller or smellier or faster, and behave accordingly. The question is: at what stage of evolutionary development did awareness of difference between oneself and one's fellows come to have a significant adaptive advantage; because that is the moment at which individuality arose as a fundamental principle of life, alongside the ability to notice it.



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