SPEAKING OF SCIENCE
Transitive inference by fish
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Transitive inference is not the monopoly of humans; we might at best be the `creamy layer'
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WE WERE taught in school to think of ourselves as Homo sapiens, the thinking humans. Such self-christening has led us to automatically think of ourselves superior to other animals — mammals, primates and even the other homos (Australopithecus, erectus, habilis, Neanderthals). Our civics teachers taught that man is a thinking animal, implying that other animals do not think.
The Swiss philosopher and child psychologist Jean Piaget went further. He called human children as little philosophers or `tiny thinking sacks'. He described the cognitive development of children to occur in four successive stages.
The four stages
An infant up to the age of two is in the sensory motor stage in experiencing the world around. Between 2 and 7 is the pre-operational stage when the child acquires and masters motor skills. The third stage between 7 and 11 is the concrete operational one.
Here the child starts thinking logically about concrete events. Beyond age 11 is when abstract thinking develops.
Piaget suggested that the operational stages are when logical thinking, or sapience, takes hold and starts developing rapidly. This is also called transitive inference by psychologists.
Here is an example of its use. Anand is taller than Ashok. Ashok is taller than Asha. So, Anand is taller than Asha. It is this wakening of sapience in us that we have prided on, and set ourselves apart from other animals. Alas, this balloon of self-glorification is getting deflated day by day.
Other animals have been shown to think logically too.
Chimps make tools
Dr. Jane Goodall showed forty years ago that chimpanzees have cognitive capabilities comparable to us (at least to our children). She has recorded the tool making abilities of these apes.
Man is thus not the only toolmaker in the animal world. Drs. Marc Hauser of Harvard and Thomas Geissmann of Hannover have described the ability of great apes to make music — solo and choral, rhythm added.
Further deflation came when the British zoologists showed about four years ago that birds are not far behind. The crow can make tools. The experiment was a take on the Panchatantra tale of the crow and the fox.
They placed a piece of meat in a tall, thin glass beaker and placed a stiff wire nearby. After some poking around, the crow took the wire, hit it repeatedly against a nearby stone and bent it to a hockey stick shape. Grabbing the bent end in mouth now, it fished out the meat at the bottom of the beaker for a happy meal!
Now comes yet more deflation . Researchers at Stanford University show that the lowly fish of the cichlid family use transitive inference a la Piaget.
Their work, published in Nature suggests that fish can infer social rank in their colonies by observation.
The fish studied, called A. burtoni, are extremely territorial and regularly engage in fights to determine social order. When they fight, it is easy to spot the winner.
Mature males have a black stripe on their face. The winner in a fight retains the stripe, while the loser temporarily loses it. After a few minutes, he regains the stripe if separated from the winner. It is these telltale marks that the researchers exploited in their experiments.
They used a large square fish tank with several removable partitions. In the central area was placed the `observer' or bystander fish, while each of the other compartments had one experimental male.
They then trained the fish to own territories by placing each of several (A, B, C, D, E) in a specific compartment. Thus, if fish B were now allowed to go into zone A by removing the partition between them, a fight ensues; Fish A will fight B off and keep its own stripe upon winning while B loses its. But of course, if A enters zone B, B wins and A loses the stripe. In each zone, the resident was always the winner, true to the nature of A. burtoni.
After such training and one-on-one fights, the researchers allowed the bystander fish from the central zone to watch the fights — A beating up B, B winning over C, C defeating D, and D dominating E.
Dominance hierarchy
The lead researcher, Dr. Logan Grosenick, says: " We were able to create an additional dominance hierarchy for the bystander fish".
Now they tested whether the bystander fish could infer (from what it had witnessed) that B was dominant over D, even though these two had not fought each other.
In order to check this, they lifted the opaque dividers between B, D and the bystander. They found that the bystander hung around with D, shying away from B. In most such cases, the bystander spent more time with the `weaker' fish.
He had figured out that it is best to keep clear of the dominant one. The fish could recognize each other on the basis of appearance alone.
In other words, the bystander was able to deduce the `pecking order' of A, B, C, D and E, by watching rivals fight and use transitive inference or TI.
TI has been shown to be used by other species such as primates, rats and birds. Now, as we go further upstream in the evolutionary river we encounter Pisces sapiens!
Debate on evolution
In 1860, a debate was held between Bishop Wilberforce of Oxford and the naturalist, Thomas Huxley, on the theory of evolution. The October 1898 issue of Macmillan's Magazine reminisced it thus.
"Then the Bishop rose, and in a light scoffing tone, assured us there was nothing in the idea of evolution; rock -pigeons were what rock-pigeons had always been.
Then, turning to his antagonist with a smiling insolence, he begged to know, was it through his grandfather or his grandmother that he claimed his descent from a monkey?
On this Mr Huxley slowly and deliberately arose and spoke those tremendous words. He was not ashamed to have a monkey for his ancestor; but he would be ashamed to be connected with a man who used great gifts to obscure the truth".
D. BALASUBRAMANIAN
dbala@lvpei.org
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