In modern psychology, what is the evidence that a personality consists of nothing more than a set of learned responses?

This question assumes that we can find one main evidence that proves such complex idea and it doesn't work that way. Also, the term modern psychology is a bit problematic since it had started at ~1879. A lot has changed ever since. The original “behaviourist” approach (first half of the 20th century) was close to the belief that there is no mental life nor internal space for thoughts and other mechanisms. The basics for this approach were led by the “classical” and “operant conditioning” paradigms. We can look at the last as learned response – subjects actively responds to stimulus in ways that they have learned in the past that will reward them. Still, the way to look at all personality as nothing but learned responses is far. The behaviourist approach was later introduced in the language theory of “verbal behaviour” – people even learn to talk by “operant conditioning”. Yet, the rise of the cognitive theory that holds empirical findings on complex mechanisms that can’t be explained only by learned responses actually contradicted the notion that personality is just a set of them. For example, the “behaviourist theory”can’t explain all manifestations of depression from a learning perspective without relating to inner mechanisms of thought and beliefs.