After a thorough behaviorist undergrad education, I had to come to grips with determinism.
I decided that those types of altruistic behavior to the detriment of the organism demonstrate that all is not stim/response (SR) determinism.
Based on evidence CONTRARY to the 5 sense, the human ON FAITH sacrifices for the benefit of the other and not him/herself.
Some will say, "...but they did what they wanted..."
No, because they went contrary to what they preferred and what their 5 senses dictated.
They transcended SR determinism.
"Greater love has no man than this; that a man lay down his life for his friends...."
The SR model helps us to make better predictions - but it is not absolute. In the end, qualia (pain/pleasure, likes/dislikes) is a very personal matter and is not constant - today your dog might do his trick for a reward of Bacon Strips, but his tastes may change at any time [even during a dog show] and it might now require a Pupparoni to get him to run the course. Lion tamers have weapons for a reason.
Love is qualia also since it can only be experienced and cannot be fully described. Love means different things to different people and at different times. The expression of a man laying down his life for his friends speaks to the greatest love.
BTW, I saw a film once of a most amazing case of altruistic behavior in the wild. A mother moose was standing with her calf when an Alaskan Brown appeared in the distance. She nudged the calf down to the ground and ran straight to the bear. She made a choice to be eaten contrary to her self-interest - and acted on it. I haven’t seen this kind of behavior outside of herds. And in the herds, such as the Black African Buffalo, it is the male who goes back to confront the predator in a battle to the death (which he often wins) - not to offer himself as an alternative dinner.
And getting back to humans (v animals) I find it particularly interesting that most all animals are born with both the ability and the instinct to find their mother's milk - but a human baby must be literally brought to the stimulus. It is as if human mothers are forced to the decision and action with a deck stacked against the newborn – as the mother’s pain is so intense during childbirth she’s apt to want to die or kill the man who did it to her. The only advantage the newborn has is that the human mother forgets that pain almost instantly.
Even so, some humans and animals are known to abandon their young. They love less it would appear.