Tirokudda Kanda: Do the dead really benefit from the gift given by the living?

Tirokudda Kanda briefly out line the benefits the dead receive from the gifts given by the living.. and there are many more injection in the Pali Cannon with similar tone. My question is are we to read these as alogorical or literally? Do the dead benefit from the offering given by their relations? I have seen these practices in Cambodia, but never had a chance to ask why and how these are done. Many thanks.