Pavlov died in 2003 after a series of heart attacks and was buried in Moscow.

This scene remains shocking, but, like most science fiction, it has aged.

And now you can see, just 10 minutes into the experiment, that we've equipped the brain by photoactivating this area to overcome the expression of this fear memory.

Animals had to be approached as physiological entities only, as Ivan Pavlov wrote in 1927, without any need to resort to fantastic speculations as to the existence of any possible subjective states.

We find patterns, we make those connections, whether it's Pavlov's dog here associating the sound of the bell with the food, and then he salivates to the sound of the bell, or whether it's a Skinnerian rat, in which he's having an association between his behavior and a reward for it, and therefore he repeats the behavior.