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How intelligent are dolphins?

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Charlotte Li

on 6 February 2015

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Transcript of How intelligent are dolphins?

The dolphin brain
Cognitive ability
How intelligent are dolphins?
Passive listening
• One study by Xitco et.al., demonstrated that dolphins can select the correct matching object in a match-to-sample task by listening to another dolphin’s echolocation as it was examining the sample object.
• It suggests that dolphins have the cognitive ability to obtain significant information about an object by listening to the echoes of another companion.
• This ability to “eavesdrop” on echoes produced by other dolphins could help dolphin social behaviours such as spatial swimming.
Johnson et.al. (2014) "Visible and invisible displacement with dynamic visual occlusion in bottlenose dolphins (Tursiops spp)" IN: Animal Cognition (18). pp.179-193.
Planning ability
Novel behaviour
Used in mating and foraging activities (e.g. separating females from a group/herding fish into balls to increase success rates). Used in addition to trial and error learning, this reflects differences seen in a population of same species
• Dolphins point at objects when they want to engage with humans - this has also been demonstrated in captive dolphins released into the open seas teaching these actions to other dolphins.
Other mammals thought to lack ability to plan, instead relying on gut instincts (exception: dog?)
Novel behaviours are demonstrated in dolphins and whales; shown by a feeding system experiment whereby dolphins learnt to pick up multiple weights instead of single ones shown by humans to save time and increase food supply (Kuczaj et al. 2009)
Rapid development of the new behaviour suggests understanding of causal relations.
Capacity to learn
In a study by Reiss et.al., 2 dolphins were marked with temporary black ink in places they could not see without a mirror. The results showed that both dolphins spent more time at the mirror when marked, thus dolphins used the mirror to investigate the markings.
Novel Behaviours
= those expressed by animals in response to particular actions, which are indicative of intelligence
Planning ability
= capacity to adapt to novel situations without simply using trial and error (solution stipulated before responding to the problem)
Other than dolphins, only Great Apes and humans also have
Mirror self-recognition (MSR)
Finally, this study implies that
self-recognition is not a by-product of factors specific to great apes and humans but instead due to a high cognitive ability and encephalization.
Contrary to the original hypothesis of "dolphinese", complex structure as seen in human language is not found
Signature whistles
function like names and are unique among non-human animals. Along with clicks and burst-pulsed sounds, they also convey emotional states or intentions as well as information about age and sex etc.
Body language
is often used as a visual form of communication
(1. Arch; 2. Flex; 3. Headwag; 4. Play dead; 5. Snit)
Humans = 7.4; Dolphins = 5.6; Whales = 2.9; Chimpanzee = 2.5; Dogs = 1.2
= measure of brain size in relation to body mass
• Much higher EQ compared to whales relative to brain mass - perhaps indicative of increased novel behaviours shown in dolphins compared to whales?
Is the brain size of humans and dolphins indicative of intelligence? Or just an evolutionary strategy to regulate body temperature?
There are
more than twice as many neocortical neurones
(neurones of the neocortex, the region of the brain involved in the higher functions such as consciousness and language) in the long-finned pilot whale/ Calderon dolphin (a member of the dolphin family) than humans. They have more neurones in this region than all of the Mammalia whose brains have been studied to date, including the great apes.
Absolute number of neurones
in the brain may be a better indicator of intelligence
Encephalization Quotient

...however we
cannot correlate the number of neocortical neurones to higher cognitive capabilities
– higher numbers of neocortical neurones does not necessarily directly mean higher intelligence. (Since humans cognitive abilities are considered more advanced.)
Moreover, dolphins possess greater folding of the neocortex than other mammals including humans.
Dolphins possess a
Gyrencephalic brain
, as in humans (unlike the smooth brain of many small mammals)
Von Economo neurons
(in humans, great apes, elephants and some large-brained cetaceans), now also reported in particular cortices of bottlenose dolphin, Risso's dolphin and the beluga whale
There is a
higher glial cell

to neurone count
. Astrocytes (type of glial cell) have been considered to be involved in coordinating the brains neural activity.
Others suggest this increased ratio correlates with rapid synapse response which is needed for fast communication in more complex brains.
“Dolphins are capable of long term social recognition, recognizing signature whistles for up to 20 years without contact between the animals”
When a dolphin copies another dolphin’s SW, he/she changes the whistle somewhat so that it stands out as a copy and doesn’t cause confusion

(sound travels 5 times faster through water than air) - bottlenose dolphin uses a distinctive high-pitched whistle (signature whistle) for all sorts of communication; vocalisation, fear and in feeding behaviours

Dolphins use a sensory sonar system to sense their environment.

Capacity to Learn
Initial plan:
1. Size of brain compared to other animals
2. Social groups & communication, inc. language
3. Cognitive ability & problem solving
4. Ethics and their basis
5. Other marine mammal intelligence
Now included:
Other characteristics of the brain, e.g. neurone type and number, gyrencephalisation
Sub-sections of cognitive ability
For and against arguments
Many people believe dolphins are the smartest animal apart from humans whilst others rank the common chimpanzee as the most intelligent species. Do different subspecies of dolphins differ in intelligence? Is the method of measuring intelligence fair across the species? Who is the smartest?​
The similarities [between humans and dolphins] suggest that dolphins qualify for moral standing as individuals-and, therefore, are entitled to treatment of a particular sort.
The differences, however, suggest that species-specific standards may apply when it comes to determining something as basic as "harm."
-Thomas I. White , Loyola Marymount University, CA [February 21st 2010]
Ethics expert Prof Tom White, from Loyola Marymount University, author of
In Defence of Dolphins: The New Moral Frontier
argues that since

exhibit characteristics that were originally only seen in humans
(eg. self-awareness) then they should be granted the
right to not be held in captivity
and should be able to live freely. His argument is backed up by Psychologist Dr Lori Marino, from Emory University in Atlanta, who explains that research has found dolphins to be far more intelligent than was previously thought.
Dolphins and other cetaceans have previously been described as
"non-human persons"
This has created much debate about whether they are entitled to protection by different legislation and an overall higher moral standing.
Intelligence is a difficult term to define as we tend to compare an animal's likeness to human ability. However, evolution to cope in different environments means that different species have developed special abilities, all of which can be termed their own form of intelligence.
If we concentrate only on human-like attributes, dolphins are indeed more comparable than some other species.
In addition, the similarities in anatomy of dolphins (and other "intelligent" animals) to humans suggests that they possess greater cognitive abilities.
We have found a variety of research that aims to support this: increased neuron number, von Economo neurons, greater encephalisation quotient...
However it should be noted that greater neuron number in particular cortices compared to humans may be a consequence of their particular lifestyle, rather than indicative of an intelligence surpassing ours.
Fig. adapted from Mortensen et al.
Interestingly, the pilot whale had higher than expected neuron number relative to body weight, but lower than expected relative to brain weight
These neurones have been thought to be responsible in the mechanisms of high social cognition abilities.
Fig. from Marino et.al. showing spindle neurons (a.k.a. von Economo neurons).
Our interest in the topic comes from past and recent incidents concerning captive cetaceans. Cases such as those seen in Seaworld have sparked questioning into the ethics and consequences of keeping these presumed-intelligent animals. If dolphins are truly of a similar mental ability to humans, there are certainly implications on their welfare in captivity.
Our aim for this project was to look into available literature that would support the belief that dolphins are of greater cognitive ability than most animals.
Views such as that featured on the right have become popular, but what is the scientific basis behind them?
Does this mean that degree of folding has implications on how intellectually advanced dolphins are? The literature seems to suggest that it is a consequence of adaptation to an aquatic lifestyle and does not mention its relation to intelligence. It has not been formally tested that increased cerebral folding is correlated with cognitive abilities akin to humans.
From Marino et.al.: The bottlenose dolphin (left) and humpback whale (right) brains shows considerable gyrification
One source (http://understanddolphins.tripod.com/dolphinbrainandintelligence.html) argues: "The more folded the cortex, the more room within the brain to house additional neurons (brain cells) with which to perform processing of information. Recently published information regarding the increased folding of Albert Einstein's cerebral cortex compared to that of other humans supports this theory."
Research and observations in recent years have revealed that whales and dolphins not only have the ability to learn as individuals, but those individuals can then pass their new knowledge onto others (especially mother-calf. This is a rare intelligence in the animal kingdom.
"Take Kelly. A dolphin who sadly lives in a research centre in the US, she has been trained to keep her tank clean. Every time she brings a piece of litter to her trainer, she is rewarded with a fish. So she’s built upon the idea. Now, when she finds a piece of paper, she wedges it under a stone, and tears off individual pieces, which she brings to the surface one at a time. Thus, a single piece of litter earns her several fish. She’s also noticed that gulls come to her tank, hungry for fish. So she uses one of her fish as bait, catches the unwary birds, and presents them to her trainers for even more food. She has not only created these remarkable strategies by herself, but she’s even passed them on to her calf."
Animal knowledge and behaviour comes from a variety of sources. Some is
, that is, they are born knowing how to show the behaviour. Others
learn from their parents
, littermates and other animals and species. Humans have previously been believed to be the only species to have this capacity to learn and also to
Youtube - "Could dolphin intelligence match humans?" uploaded by ThickShades1
More convincingly, their ability to exhibit a range of behaviours is reflective of a complex mind. Their playful nature and inquisitiveness plus the ability to learn from individuals of the same or other species, shows that they have great cognitive potential.
From the BBC's 2003 Wildlife on One special Dolphins: Deep Thinkers?
Uploaded to Youtube by pacificwhitesided
Mortensen, H.S. et al (2014) “Quantitive relationships in delphinid neocortex”. IN: Frontiers in Neuroanatomy 8:132. doi: 10.3389
This has also been demonstrated by a prey detection experiment by Gannon et al, who showed that dolphins would often use passive listening over echolocation when foraging to conserve energy.
(excerpt taken from WDC webpage on learning "Brain Power")
There has been less research into other animals about their potential to exhibit new behaviours
Occurs in conjunction with planning behaviour.
Jaakola et al showed that bottlenose dolphins fail to demonstrate an understanding of
object permeance
, the ability to reason about objects that have disappeared from view. This ability has however been shown in various species of great apes and psittacine birds.
The dolphin's large brain is theorised to relate to thermoregulation (prevention of heat loss in the aquatic environment).
Kuczaj, S.A., Gory, J.D. and Xitco Jr., M.J. (2009). How intelligent are dolphins? A partial answer based on their ability to plan their behavior when confronted with novel problems. The Japanese Journal of Animal Psychology, 59 (1): 99-115
RIT (Rochester Institute of Technology) ‘Brain & Behavior Psych - Dr David A Kaiser’. www.rit.edu/~dakgsh [Accessed 18th December 2014]
National Geographic ‘Animal Minds’. http://ngm.nationalgeographic.com/2008/03/animal-minds/virginia-morell-text [Accessed 18th December 2014]
Dolphin Research Center ‘Dophin Communication’. https://www.dolphins.org/communication [Accessed 18th December 2014]
Xitco, M.J. Jr and Roitblat. H.L. (1996) Object recognition through eavesdropping: passive echolocation in bottlenose dolphin Anim. Learn. Behav. 24,355-365
Reiss, D. and Marino, L. (2001) “Mirror self-recognition in the bottlenose dolphin: A case of cognitive convergence” PNAS 98:10 5937-5942 doi: 10.1073
Gregg, J. (2013) "Dolphins aren't as smart as you think" [online] Accessible at: http://www.wsj.com/articles/SB10001424052702304866904579266183573854204. [Accessed 4th Jan 2015]
Kriesell, H., Elwen, S., Nastasi, A., & Gridley, T. (2014) 'Identification and Characteristics of Signature Whistles in Wild Bottlenose Dolphins (Tursiops truncatus) from Namibia', Plos ONE, 9(9), pp. 1-13.
Janik, V, & Sayigh, L 2013, 'Communication in bottlenose dolphins: 50 years of signature whistle research', IN: Journal Of Comparative Physiology. A, Neuroethology, Sensory, Neural, And Behavioral Physiology, 199(6) pp. 479-489.
Stollznow, K. (2014) 'Bad language: speaking the same language? Research into dolphin communication', Skeptic (Altadena, CA), 3, p.6.
Schaefer, L. (online) http://understanddolphins.tripod.com/dolphinbrainandintelligence.html. [Accessed 15/01/15]
WDC: Brain Power (online) http://us.whales.org/whales-and-dolphins/brain-power. [Accessed 15/01/15]
Gannon, D.P. et. al. (2005) "Prey detection by bottlenose dolphins, Tursiops truncatus: an experimental test of the passive listening hypothesis". IN: Animal Behaviour 69 (3), pp. 709-720.
Jaakola, K., Guarino, E., Rodriguez, M., Erb, L., Trone, M. (2010) What do dolphins (Tursiops truncatus) understand about hidden objects? IN: Animal Cognition 13, pp.103-120.
Other anatomical adaptations have been suggested to be a consequence of their evolution in such a habitat. Huggenberger proposes that a rudimentary pelvic girdle means that there is less limit to brain size during development. In addition, the gyrification is a way of compensating for a simply structured neocortex.
However, Johnson et al have argued that the failure was likely to be a result of object containment rather than low cognitive ability.
Huggenberger, S. (2008) "The size and complexity of dolphin brains - a paradox?" IN: Journal of the Marine Biological Association of the United Kingdom. 88(6) pp.1103-1108.
Dolphins emit high-pitched clicks which bounce off objects. The dolphin uses the echo that travels back from the object to sense its size, shape, and speed.

Used for navigation, finding prey, avoiding hunters, locating missing members of their pod
Marino et al. comment: "Self-knowledge, including self-awareness, enables one to develop a self-image and monitor and evaluate one's own behaviors."
Unlike chimpanzees, dolphins pay less attention to markings on the bodies of companions because dolphins do not social groom like chimpanzees. This makes the study even more interesting because “dolphins clearly are interested in marks on their own body despite the fact that they do not have a natural tendency toward social grooming”.
When one dolphin was marked for the first and only time on the tongue, it immediately swam to the mirror and “engaged in a mouth opening and closing sequence never before observed by him during the study”.
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