There is an effect, which I will call “quantitative numbing,” that results in greater quantities of things that concern us producing less rather than more concern. This is an expression of “psychic numbing,” which is well documented. This phenomenon is chillingly described in a quote that is probably misattributed to Joseph Stalin, “A single death is a tragedy; a million deaths is a statistic.” According to Paul Slovic and Daniel Västfjäll, in a chapter titled “The More Who Die, the Less We Care” that appears in the book Numbers and Nerves:
There is considerable evidence that our affective responses and the resulting value we place on saving human lives follow the same sort of psychophysical function that characterizes our diminished sensitivity to changes in a wide range of perceptual and cognitive entities—brightness, loudness, heaviness, and wealth—as their underlying magnitudes increase. As psychological research indicates, constant increases in the magnitude of a stimulus typically evoke smaller and smaller changes in response. Applying this principle to the valuing of human life suggests that a form of psychophysical numbing may result from our inability to appreciate losses of life as they become larger. (Numbers and Nerves: Information, Emotion, and Meaning in a World of Data, Scott Slovic and Paul Slovic, editors, 2015, page 31)
This effect exhibits a logarithmic pattern, with larger numbers resulting in a diminishing response. Slovic and Västfjäll go on to point out, however, that feelings of compassion suffer an even greater loss as quantities increase. In fact, increases in the growth of compassion are not merely reduced as quantities increase, but compassion actually decreases and does so quite dramatically.
For example, studies have shown that charitable contributions in response to appeals are greatest when intended to help a single individual, are reduced somewhat when helping two, and decrease at a greater and greater rate as the numbers grow. Beyond a certain threshold, we stop giving altogether, even to save lives.