Immunisation.....if you lived in an underdeveloped country where food resources and famine were scarce, then you would (your brain) become immune to the scenes that you see......dead bodies, dead cats, children dying etc.
It would be "business as usual", bur we in the Western world are still susceptible to such scenes and it affects our sense of dignity, up bringing, decency, whatever one would like to call it.
Our "immunity" to such things does improve due to age and repetition and i must admit, that seeing starving children., dead bodies, flooding rape and pestilence which at one time would disturb me, leaves my now......unmoved.
Immunisation.