Here is a great piece on Pavlov – in the New Yorker - a review of a new biography by Daniel Todes, who also has an article/22 piece listicle on Pavlov on the OUP blog which is well worth reading. Among many nuggets, Pavlov seemingly characterised his own foul temper tantrums as “spontaneous morbid paroxysms”; didn’t a get a tenured position until the age of 41; believed in free will; was an art collector; and gave up science for three months every summer.
To get some context on these times in Russia, there are many books to read: a few of my favourites include The Dark Valley: A Panorama of the 1930s; Stalin and His Hangmen; Lenin: A Biography by Robert Service; and Simon Sebag Montefiore‘s biographies of Stalin. Death was everywhere in these times – whether through famine, collectivisation or conviction as an enemy of the people. Scientists were just as much a target as anyone else:
‘a third of Pavlov’s colleagues at the Russian Academy of Sciences died in those first post-revolutionary years’.
Defiance of the Soviet Government was almost impossibly dangerous, but yet Pavlov defied the Soviets and more remarkably – was allowed to:
“…Stalin began a purge of intellectuals. Pavlov was outraged. At a time when looking at the wrong person in the wrong way was enough to send a man to the gulag, he wrote to Stalin saying that he was “ashamed to be called a Russian.””
Given the usual consequences of the Gulag or the cellars of the Lubyanka of such defiance and outspokenness, this was brave or foolhardy or perhaps some combination of the two. I’ve written briefly about this time in Soviet psychology – on Bluma Zeigarnik and the Zeigarnik Effect, and Bluma’s very brave neuropsychologist friend, Susanna Blumenshtein. Mindhacks are probably being a little ungenerous regarding Pavlov; these were terrible times in Russia.
A hundred years later, Pavlov’s work lives on in all sorts of ways. A particularly busy literature is Pavlovian-instrumental transfer (PIT), where conditioned stimuli may affect the expression of ongoing instrumental responses – an important phenomenon as it shows that conditioned stimuli can enter into the control of instrumental behaviour, despite not having being explicitly trained. A simple example is where a rat is in an operant box: the houselight is turned on, and a food-pellet released into the food hopper. This pairing occurs multiple times, so the houselight comes to predict pellet release. The rat is later trained to press the lever for food pellets. The house light being turned on lever pressing enhances the lever pressing (instrumental) response – there is transfer of training between the two types of learning. So, if the houselight is turned on during lever-pressing, the rate at which the rat presses the lever increases. But why?
this effect has been further subdivided into specific and general PIT. Specific PIT happens when the CS is paired with the same reward of the instrumental action. Instead, general PIT happens when the CS is paired with a different reward. In both cases, the presence of the CS leads to higher instrumental responding, however, different neural substrates are involved. Specific PIT involves the basolateral amygdala and the nucleus accumbens shell. General PIT involves central amygdala and the nucleus accumbens core
Of course, knowing the neural substrates is useful, but we still need to understand at a representational level the rules this form of learning obeys.
One thing that strikes me about PIT: is it a point of demarcation in learning between vertebrates and invertebrates? I have not been able to find any papers showing PIT in non-vertebrate species – this might be the inadequacy of my literature searches. PIT involves the learning of differing inter-temporal stimulus relations, as well as modifying ongoing behaviour. It might well be beyond the representational capacity of the invertebrate nervous system.