Behavior: Researching the behaviour of dolphins in the wild is a difficult task. However several researchers have examined the social behaviour of dolphins and tried to extract from an understanding of the level of communication between individuals, which in turn is interpreted as a measure of intelligence.
Dolphin groups sizes vary quite dramatically. Older male Orca tend to lead quite solitary lives but this is the exception. River dolphins usually congregate in fairly small groups, from 6 to 12 in number. Researchers expect that the individuals in these small groups may well know and recognise each other. Other species such as the oceanic Pantropical Spotted Dolphin, Heaviside's Dolphin and Spinner Dolphin travel in vast crowds, sometimes thousands in number. It is extremely unlikely that every member of the group is acquitanted with every other, as this would require more social interaction than found in humans. However there is no doubt that such large packs can act as a single cohesive unit - observations show that if an unexpected disturbance such as a shark approach from the flank or from beneath the group occurs, the group moves in near unison to avoid the threat. This means that the dolphins must not only be aware of their next-door neighbours but also other individuals near by - in a similar manner to which humans perform "Mexican waves". This is achieved by sight, and possible also echolocation. One controversial theory proposed by Jerison (1986) is that the pack of dolphins are able to share echolocation results between each other to create a better understanding of their surroundings. In the Encyclopedia of Marine Mammals Bernd Wersig compares this to a group of humans being able to share exactly what they can see with each other and so create a better 3D visual representation for all. Jerison goes to speculate that these "shared data" echolocation maps might account for the relatively large dolphin brain discussed above. This idea has not received much formal backing in the literature.
Communication: Should be a sub section of communication abilities
some studies have made wild claims
need to criticise methodology as well.
Learning and memory: Should be a section on learning skills. Scientific tests relevant to:
Learning tricks - dolphins have been taught extremely complicated tricks.
Lying and subterfuge - there are some studies which suggest ability to use subterfuge. Dolphin training the trainer suggestions
Learning to learn - there was a study on the ability to learn that a variable response was required to get a reward. Did similar study on humans and compared.
Long and short term memory
Ability to abstract
Need to criticise the methodology of these studies
Not only have dolphins exhibited the ability to learn complex tricks, they have also demonstrated the ability to produce creative responses. This was studied by Karen Pryor in the mid-sixties at Sea Life Park in Hawaii, and was published as "The Creative Porpoise: Training for Novel Behavior" in 1969. The two test subjects were two rough-toothed dolphins (Steno bredanensis), called Malia (a regular show performer at Sea Life Park) and Hou (a research subject at adjacent Oceanic Institute). The experiment tested when and whether the dolphins would identify that they were being rewarded (by fish) for originality in behaviour. So the trainer would reward the dolphin for a novel behaviour, but would not if the same behaviour was repeated. The experiment was highly successful. Malia finally learnt what was expected after a few days and from the fifteenth session produced an original behaviour to get a reward. Hou took thirty three sessions to reach the same stage. On each occasion the experiment was stopped when the variability of dolphin behaviour became too complex to make further positive reinforcing meaningful.
However, though this impressed researchers at the time, experiments by Neuringer(1992)
and others have shown that other animals like pigeons and rats can likewise
be trained for variability of response, which given time can result in apparently
original behaviour. Whether there is a clear case for dolphins showing real
creativity in this experiment is therefore questionable. Arguably the quality
of the dolphins' response was far superior, but further research is required
in this area to test this.
Self-awareness: The ability to possess self-awareness shows a highly developed abstract thinking. Self-awareness is the precursor to more advanced processes like meta-cognitive reasoning (thinking about thinking) that are typical of humans. Scientific research into self-awareness has suggested that Bottlenose Dolphins possess self-awareness. Dolphins differ markedly so an assessment can not be made for all species, some of which have much smaller brain sizes and presumably different structures.
The standard test for self-awareness in animals is the mirror test, developed by Gallup in the seventies, in which a temporary dye is placed on an animal's body, and the animal is then presented with a mirror. Most animals react to a mirror as if it is another animal. However, like great apes, dolphins have been shown to recognise the mirror image as themselves, by examining the marking on their body. Evidence for mirror recognition by dolphins was anecdotal until the nineties, but the scientific studies carried out by researchers Marten and Psarakos (1994, 1995) and Reiss and Marino (1998) confirmed it.
Some scientists still disagree with these findings arguing that the results of these tests are open to human interpretation. This test is far less definitive than when used for primates because primates can touch the mark or the mirror, while dolphins cannot, making their alleged self-recognition behaviour less clear. Critics argue that behaviours that are said to identify self-awareness resemble existing social behaviours, and so researchers could be mislabelling social responses to another dolphin. The researchers counterargue that the behaviours shown to evidence self awareness are very different to normal responses to another dolphin, including paying significantly more attention to another dolphin than towards their mirror image. Dr. Gallup called the results "the most suggestive evidence to date" of mirror self-recognition in dolphins, but "not definitive" because he was not entirely clear that the dolphins were not interpreting the image in the mirror as another animal.
As a further response to these criticisms Marten and Psarakos(1995) used
television to test dolphin self awareness. They showed dolphins real time
footage of themselves, recorded footage and another dolphin. They concluded
that their evidence suggested self-awareness rather than social behaviour.
This study has not been repeated since then however, so the results remain
Conclusion: It is difficult to establish the level of intelligence in dolphins. Not least because it is difficult to decide on an appropriate criteria for intelligence. Are homocentric standards of intelligence suitable for water-based dolphin species? Despite scientific study for over forty years scientists are little closer to definitive answers. We can say that average dolphin intelligence is somewhere on the continuum between above-average(?) human and peak dog, but we cannot say definitively where.
References: A scholarly page at the University of Colorado, Boulder.
An AAAS Science Netlinks feature.
Article from the Guardian about dolphin intelligence