Ryan Enos published a fascinating study both methodologically and substantively. The study estimates ``the causal effects of repeated intergroup contact, in which Spanish-speaking confederates were randomly assigned to be inserted, for a period of days, into the daily routines of unknowing Anglo-whites living in homogeneous communities in the United States, thus simulating the conditions of demographic change.’’
The top line in the figure above shows the ATE of people that had 3 days; the bottom line shows 10 days. Higher values indicate a a larger difference in exclusionary attitudes between treatment and control. The fact that the effects get smaller with more contact adds a wrinkle to the story. Maybe intergroup contact increases threat temporarily. Perhaps after a month or two, the effects may go the other way (more supportive of immigration), and, therefore, in line with Allport and intergroup contact.