While it’s not a scientific study, Jeaneane Fowler had some fairly good responses/thoughts to this question in her book “Humanism: Beliefs and Practices”. I’m looking for it right now.
Humanists believe in only one life and it is therefore important that it ends in the kind of dignity and quality with which that life was lived. In principle, this is compassionate, and Humanists claim that it is wrong to deny people such compassion out of fear of abuse of such principles by a small minority. This is unfair to the suffering.
The idea is to live life to the fullest and when death comes it can hopefully be faced head on with courage just as life was faced with courage.
The Value of life- page 37:
Humanism does not accept that there is life after death, and therefore one has to reassess life in relation to the present. Death is final, and that makes life more precious.
The Humanist begins his choice of life by choosing to live.
If fear of death and belief in God serve to make an individual put all his or her eggs into the afterlife basket instead of into this life, then that individual is only living half a life.
This could be the key- Humanist do charish life and try to live it to its fullest.
Death is a common denominator for all humanity, it cannot be ignored. But the best way to put it in perspective is to ensure that the life which precedes it is full, fruitful, dynamic, self-evolving and self-assertive in ways that not only enhance an individual life, but which also serve to enhance the society within which one is placed.
First, you can do as much good as you can, give as much love to your fellow human beings as you can, but you will never benefit from this until you die. This makes death optimistic, but it is wholly pessimistic about life. Second, while Christians are told that they ought to be humble, the idea of of personal reward in heaven promotes egoistic self-interest and elitism; the good one does is for one’s own rewards. This is seen both individually and collectively.
This world is more important than the next one, for if human beings do not know how to find value in life, then death will be feared.
This is where Humanists differ from Christians. We try to find meaning to life. We do things for others because we want to do them, we want to bring the “good life” to everyone we possibly can, unselfishly and without any expectation of a reward. We find pleasure in doing things for others and in enjoying this life, because we know this is it and we must charish the time we have here.
Secular Humanists reject this kind of negative view of the present existence, and the concept of life in a wonderful existence beyond the grave in some kind of resurrected and reconstituted physical body. The rejection of dualistic conceptions of the self, and the rejection of a theistic, anthropomorphized deity who rewards and punishes those who worship or reject him respectively, makes belief in an afterlife unnecessary. Secular and atheistic Humanism believes that this life is all that we have, and we should therefore be optimistic about what we wish to do in it and what we are able to do in it. It is a positive view of life, with high expectations for individuals within it. Rewards are not in heaven, they are on earth, and they are both necessary for the individual in his or her own realization of personal goals, and for broader, societal and global benefit. What greater reward can a person have in life, than to know that he or she leaves behind at death some contribution to a better world?
When the finitude of life cannot be faced with courage, then life is lived with a deep subconscious fear and profound dread of death. Part of the Humanist outlook is the fostering of a healthy attitude to death, and an openness in facing it as the total extinction of a life.
The optimism about life and the healthy attitude that is fostered is proably what prepares us better for death. Christians are so concerned about achieving an afterlife that they fear death more. They fear they did not do what they needed to do in order to get to Heaven. We Humanists don’t worry about that. We are more concerned with living this life, our only life, to it’s fullest, thus death is less feared.
I’m not sure if this helps to answer your questions, but I think it is something to ponder towards finding the answer to the question. I also think Paul Kurtz mentioned something about this in one of his CFI interviews too.