Can We Really Give Altruistically?

Question: 1. Rebbe, is there really such  a thing of loving someone or doing something for someone else just because you want to give to them in the purest sense? I know that Ahava comes from the word Hav, which is give, but I think that according to psychology the only reason why we would give is because we get something back in return.  2. Isn’t it the same in a marriage. It’s not just giving because if you would only give and your spouse does not give back then you would not want to stay with them. So then wouldn’t it be a codependent relationship in terms of giving and taking, and therefore one can say that the motives behind the giving are ultimately how your spouse treats you after you have put in the effort by giving to your spouse and making them happy? Obviously you want your spouse to be happy but is it just because you enjoy it when they are happy? Even if someone gives their life for someone else can’t you say it’s because they wouldn’t want to live without them. I know there is something more to love and giving but I according to psychology there might not be. Why wouldn’t psychology be correct?