|The Punishment of Loki, by Luis Huard, 1900|
Mark Kleiman quotes his colleague Ed Witney:
“Voters should think twice before delivering great political power into the hands of men who show a strong urge to punish. Those who neglect this principle will not remain free or safe for long."
Punishment definitely affects behavior - technically, by scientific definition it means that the behavior has reduced or stopped. But what we're really talking about is the application of aversive consequences after a behavior, and this definitely works.
That said, it's far more complex, obviously. I'm reminded of a classroom of teenagers I once worked with at a continuation (at-risk) school. I asked them to raise their hands if they had been spanked as children - almost every single hand went up. These kids were horrendously behaved, and yet came from homes in which corporeal punishment was the norm. There is also evidence that this type of punishment teaches physical aggression through modeling. Punishment tends to be more effective short term, as the individual learns avoidance strategies. It also requires consistency - if punishment is delivered inconsistently, it weakens dramatically.
Far better, is positive reinforcement: applying enjoyable consequences immediately following appropriate behaviors. This not only strengthens the behavior you want, but allows for targeting and shaping new behaviors that are more functional and will bring the individual into contact with natural contingencies. For example, punishing a child for not doing his homework doesn't specify what skill you want to increase. Better to reward specific study skills such as organization, following a schedule, attentiveness, self-regulation, etc.
All of this gets quite complex, as there are specific factors unique to every context. But as a rule, positive reinforcement is far more productive. You can do both however: inappropriate behaviors can be punished while appropriate behaviors are rewarded. But too often the latter are forgotten (it's natural to notice poor behavior more than good).
In my work with families the most difficult barrier to behavior change in children is often a culture of punitive discipline. There is a dynamic of anger, resentment and hostility. When delivered consistently and with love, this isn't too much of a problem. But more often than not the loving, compassionate side loses out to a constant refrain of disappointed criticism. My work is to support the parents in learning to deliver more positive reinforcement by focusing on the behaviors they want from their children.
This of course applies not only to children but to everyone: spouses, friends, co-workers. Focus on the positive and reward want you want with smiles, compliments, etc. For the behaviors you don't want, give clear, immediate and strong feedback, but don't dwell on it. How we all respond to others has a huge impact on their behavior.
I'm less comfortable extrapolating this to national politics and policy. But with specific context taken into account, the same principles will apply. Speeches I doubt have much behavioral impact. But policies and programs certainly do. Organizational behavioral management is a field in which policy-oriented topics are studied.
To note: everything I have said is based in behavioral science, and as such assumes a deterministic view of human behavior, in which our behavior is learned based on our genetic predispositions interacting with the environment. Free will is irrelevant, and as such so is blame. What matters is the system over time.