25 years ago? I'm in my 50's now and I remember this change happening when I was in my teens. 35-40 years ago maybe.
The WBTS insisted that the heart was where things like emotions come from, not the brain. Even as a teen, I assumed it was figurative, though one day I was assured the Society did in fact not take it figuratively. They thought it literal.
My brother and I, who had middle school and high school science thought this was utter BS. The heart is a muscle that pumps blood. It has no control over higher functions like emotions. And my brother and I kind of laughed that anybody would be stupid enough to take that literally.
Upon which, our parents got real serious quick. We were to shut up about what we thought and NOT to ever speak to anybody at the hall about it. As I recall, and I might be wrong, I think it was kind of to the effect of "you can think that if you want, but don't ever let anybody know you think that".
As I recall it, the first artificial heart was used in 1982. And shortly afterwards, the society changed it's mind and published that the heart was a figurative seed of emotions, not literal. I figured the society realized after the first person with an artificial heart still had emotions, they didn't originate in the heart, so they HAD TO change.
Though we still followed the religion, that was eye-opening. WE (my brother and I) were right all along. BEFORE the society. What's up with that? Shouldn't the holy spirit have guided them to the correct understanding in the first place? Obviously the GB was not ALWAYS right. And people could have the correct understanding when they did not. Kids in their early teens knew more about biology than they did.
AND, that the bible is not always correct. Now, that's probably an example that's open to interpretation. Obviously you could say the bible was figurative all along. But that whole thing probably planted seeds that were to grow later about both JWs and the bible itself.