Read the following passage and answer the questions given below.
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 complex brains, recognize themselves in the mirror, use tools, have ‘names', display some linguistic competences, and have self-awareness. Due to these observations, some scientists even demand that dolphins no longer be kept in captivity. These arguments have a political impact and countries like India have decided that ‘cetaceans should be ________ “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 and hippocampal neuroanatomy of cetacea and came to radically different conclusions. In the last issue of Neuroscience, Manger 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?
Dolphins live in a primarily acoustic world and use a variety of auditory signals for communication. They use learned vocal labels to address each other, exchange signature whistles when meeting, and use their learned whistles in matching interactions in which an individual responds to a whistle of a conspecific by emitting the same whistle type. Studies in captivity have even revealed a certain understanding of syntactic properties in sequences of sounds and gestures. Especially Louis Herman made an impressive scientific lifetime achievement in demonstrating that dolphins understand referential pointing, report the presence or absence of objects, and understand imperative ‘sentences' delivered in either acoustic or gestural format. These ‘sentences' consisted of units that represented objects, actions, agents, and modifiers. They could be combined by rules such that hundreds of different complex commands could be produced. Dolphins also seem to understand the identity of humans and their TV representations since they also followed gestures from video displays, although with some constraints.
These cognitive achievements are certainly highly impressive. But, as pointed out by Manger, similar results could also be obtained from other species. Both chimpanzees and bonobos can learn and combine large numbers of symbols or gestures that stand for objects and actions. Chimpanzees produce functionally referential vocalizations which encode sufficient information about objects to allow conspecifics to respond accordingly. Also, a California sea lion quickly learned equivalence classes between symbols as a possible means for referential communication.
Some dogs can not only learn the names of more than 200 different toys but also acquire new names by exclusion such that the dog attends to a new toy when hearing a novel word. However, there is no evidence that dogs acquire syntactic rules. Also, some parrots label and address conspecifics and the receivers primarily respond to calls that address themselves. This is similar to the usage of whistles by dolphins to address other individuals. Alex, possibly the most famous parrot ever, not only learned English words to referentially label many objects and their colours but also used short phrases and understood that the same object could be defined by material, colour, shape, and object name. These data demonstrate that the ability to learn and to combine a large number of referential symbols and use them with a small set of syntactic rules is within the reach of several nonhuman animals from the avian and mammalian classes. Bottlenose dolphins are not alone.