Salivating dogs, Russian scientists and learning

Language: Portuguese

How can a dog's salivation bring us knowledge about the learning process? To understand a little about this we need to go back to the 1920s, in Ivan Pavlov's laboratory. Pavlov was a Russian physiologist, Nobel Prize winner, who specializes in the digestive system. His works contributed significantly to the growth of the behavioral and physiological sciences. His studies have initiated a new behavior-related science that ranges from aspects of the biological, physiological, and also psychology.

For his research on the digestive system, Pavlov used equipment that measures the production of saliva in dogs. As for saliva, dogs normally salivate in response to the smell of their food that they find palatable, this is a reflex response and independent of cognition. It is known that when food is brought to a dog, naturally there is an increase in the production of saliva. However, unlike what was known at the time, Pavlov began to observe this effect when dogs perceived the presence of the caretaker, regardless of the presence of food.

This observation led Pavlov to a deeper investigation of this phenomenon. For this he used stimuli that can be more controlled, like the noise of a bell, to carry out his experiment. Pavlov's experiment consisted of presenting the stimuli to the dogs and observing the production of saliva.

At first, both stimuli were presented together, ie the smell of the food along with the bell noise was presented simultaneously - he called this stage the "acquisition phase". After this combination was presented several times Pavlov presented only the noise of the bell. What he observed was a phenomenon never previously described: the dog began to salivate soon after hearing the bell. The four phases of Pavlov's experiment are illustrated below.

He also noted that if he continued to present only the noise of the bell the dog's response would decrease until it died out. Pavlov's experiments begin studies on Classical Conditioning and show that animals have the ability to alter their behavior in a way that adapts their response to environmental stimuli, improving their ability to survive.

Salivation is an involuntary response, does this work for voluntary behavior? It was later discovered that it also works for behaviors that are voluntary. In the 1950s Ernest Hilgard began studying classical conditioning in humans, he set up an experiment, similar to Pavlov's, in which a sound stimulus was presented and shortly thereafter a small jet of air was thrown into the participant's eye. The act of closing the eyes is voluntary, but even so, Hilgard noted that the sound stimulus conditioned the closing of the eyes.

One of the most important factors in these Pavlov and Hilgard experiments is that they were one of the first to approach learning in a systematic way. This was a very important step in the history of psychology and neuroscience since it allows the study from the observation of behavior, something external and measurable, not inferences about the mind or thought, which are internal and less objective processes.

As Pavlov would say, in a free translation:

"Humanity will have untold advantages and extraordinary control over human behavior when the scientist is able to subject his fellows to the same external analysis that he would employ with any natural object, and when the human mind beholds not from within but from without."

- Ivan Pavlov, Scientific Study of So-Called Psychical Processes in the Higher Animals.

The contributions of Pavlov and Hilgard's work are central to the vast majority of behavioral and neuroscience studies. The knowledge established from classical/operant conditioning is the basis for the great majority of studies with animal models in neurosciences that are behavioral dependent. Conditioning concepts are used to assess the locomotor pattern, exploratory, anxiety levels, smell aversion of predators and etc (as can be seen in the image below).

References

Pavlov, P. I. (2010). Conditioned reflexes: an investigation of the physiological activity of the cerebral cortex. Annals of Neurosciences, 17 (3), 136.

Hilgard, E. R., & Bower, G. H. (1966). Theories of learning.

Suzuki, S., Augerinos, G., & Black, A.H. (1980). Stimulus control of spatial behavior on the eight-arm maze in rats. Learning and motivation, 11 (1), 1-18.