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Measuring The Immeasurable

Measuring The Immeasurable

I had never been a fun of non-fictional books but as the years went by I found myself picking up more books that fall under this category and finding them an enjoyable read. Most of these books were read on recommendation,and one such great read was “The Ten Most Beautiful Experiments” by George Johnson, describing experiments that discovered what we may now consider basic science. Some of the experiments described were new to me, all the experiments were indeed beautiful and I couldn’t help but acknowledge the intricate and delicate designs of these experiments. So here is my take on one such experiment; Ivan Pavlov’s conditioning experiments described by George Johnson in the chapter “Measuring the immeasurable”.

A genius collection of geniuses at work


The son of a Russian priest, Pavlov was headed down the same path until he discovered the writings of Darwin amongst others. He soon went to study under Mendeleyev (The guy who gave us the periodic table) in Saint Petersburg and about 20 years later he became head of Physiology at the Institute of Experimental Medicine. Pavlov worked with his pet/lab dogs who were really personal to him, with names such as Spot, Weasel, Old russian prince and Genghis Khan. He discovered that salivation and gastric juices contained enzymes which were specifically secreted dependent on the food to be digested and this work on the digestive system won him a Nobel prize in 1904. This was when he switched into the study of the nervous system because apparently the field was lacking strong players and who better to recruit than a Nobel prize laureate. Whoever thought winning the Nobel prize was the peak of a scientist career obviously never heard of Pavlov because this is where his true contribution to science begins.


During his ‘digestive system’ experiments, Pavlov noticed what any dog owner will undoubtedly know; it is not just the food that caused the animals to salivate. Overtime just the sight of the food bowl, the opening of the cupboard at feeding time or pretty much anything that consistently happened before feeding was enough to make his dogs salivate. Not knowing what else to make of this, he named them ‘Psychic secretions’. Unlike the natural ‘unconditional’ salivation that occurred when the food was presented to a dogs, these ‘Psychic secretions’ were learned through life. His dogs would salivate more in anticipation of food or stop salivating if you kept teasing them with food. This whole idea of psychic secretions were ‘conditional’. It is all well and good noticing this, but how do you prove for a fact that a supposedly innate instinct of the dog could be controlled by a man. Switched on and off, turned around, diminished and enhanced like some dimmer switch. At the time, this work was neccessary to bridge the gap between the physical world and the mental world.


The solution is quite simple really; set up a series of experiments to show that you can make your dogs salivate to anything of your choosing. Pavlov moved all his dogs to a specially built unit where he had as much control as possible over everything the dogs were exposed to. This included the sights, sounds, smells and even vibrations from nearby buildings. Strict timetables were maintained for everything and all dog-man interactions were also controlled. At the time, many may have considered the steps taken to be a bit over the top but what he showed by these experiments was nothing short of beautiful. He could make his dogs salivate to the most random things such as the ticking of a metronome, a light flash, the sound of a horn, specific musical notes and even the rotation of an object (this could be further specified; clockwise or counter-clockwise). The only conditions to pull off these experiments were consistency in terms of context and a close timing between the ‘unconditional’ stimulus (random stimulus of your choosing) and  the meat (conditional stimulus).


Nowadays experiments that try to investigate animal behaviour use some kind of test based on Pavlovian conditioning. His work has come so far that these experiments are used to test various things such as memory, tinnitus, hearing impairments, genetic mutations and vision. Basically if you need an animal to answer ‘Yes’ or ‘No’ to pretty much any question of scientific interest, Pavlovian conditioning is the way to go.

Pavlov’s work will forever be remembered and in recognition of the dogs that contributed to this most beautiful experiment, ‘Monument to a dog‘ was set up at the Institute.

Image by Sergey Grachev

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