Related to psychic numbing, the singularity effect is the name to how we care disproportionately about an individual as compared to a group. Think, Saving Private Ryan, where an enormous effort is launched to save a single soldier in the second world war. It turns out that even as you add a second person there’s some justification for something known as compassion fade. The addition of more people doesn’t increase our willingness to help proportionally — our compassion fades as more people are involved.
Once again, see the work of Paul Slovic.