The "Identified Victim" Effect.

Kogut & Ritov (2005)
Summary by 
Mark Egan

The authors looked at willingness to donate when victims were presented alone or in a group. Their study used a 2x2 design of (single victim vs group) x (identified provided victim vs unidentified) and examined peoples’ Willingness to Contribute, feelings of distress and empathy towards the victims.Results showed people donated more to the individual victim rather than the group of 8 when both were identified (i.e. name, age and picture provided) but donated more to the group when both were unidentified.This is with the proviso that standard deviations were quite large for monetary donations. Of the 4 conditions, participants felt the most distress and empathy for the identified single victim.