Is Dolphin Cognition Special?

complex brains, recognize themselves in the mirror, use tools, have ‘names’, display some linguistic competences [Marino, 2004], and have self-awareness [Herman, 2012]. Due to these observations, some scientists even demand that dolphins no longer be kept in captivity [Marino and Frohoff, 2011]. These arguments have a political impact and countries like India have decided that ‘cetaceans ... should be seen as “nonhuman persons” and as such should have their own specific rights’. But how strong is the scientific evidence for the cognitive exceptionality of dolphins? Manger and colleagues extensively reanalyzed the cortical [Manger, 2006] and hippocampal neuroanatomy of cetecea [Patzke et al., 2013] and came to radically different conclusions. In the last issue of Neuroscience, Manger [2013] also reviews the dolphin cognition literature and draws a quite sobering conclusion. But is his critique justified or does he throw the baby out with the bathwater? Before going into the details, a relevant specification of the battlefield seems to be in order. Manger [2013] refers to ‘cetaceans’ in the title of his paper but the vast majority of references of behavioral studies are to bottlenose dolphins. The order of Cetacea contains two suborders: Mysticeti (baleen whales) and Odontoceti (toothed In 1969, Hodos and Campbell [1969] published a landmark paper with the title ‘Scala naturae: why there is no theory in comparative psychology’. In it, the authors argued that many comparative psychologists of their time followed the concept of a continuous cognitive phylogenetic scale with diverse species ranked according to increasing levels of intelligence. This concept mostly rested on arbitrarily chosen behavioral tests whose outcomes were used to create ranks like ‘goldfish – pigeon – rat – cat – monkey – human’. Although these rankings seemed to have some face validity, this approach was full of problems and was in its essence unscientific. The most important problem was that slight changes in the experimental procedure could importantly alter the ranking, demonstrating that not cognitive but rather perceptual, motoric, or motivational limitations had determined the outcome. The paper of Hodos and Campbell [1969] marks the end of the scientific search for a general ‘nonhuman IQ’. Only for dolphins and chimps do some scientists still argue that there is sufficient evidence for their overall cognitive superiority to the extent that these species should be set apart from other nonhuman animals. In the case of dolphins, their arguments are usually two-fold: bottlenose dolphins (and other cetacean species) have very large and Published online: January 30, 2014