Irregularities in LaCour (2014)

modified 2018-10-11

Irregularities in LaCour (2014)

In short

We report a number of irregularities in the replication dataset posted for LaCour and Green (Science, “When
contact changes minds: An experiment on transmission of support for gay equality,” 2014) that jointly suggest
the dataset (LaCour 2014) was not collected as described.


A straightforward procedure may generate these anomalies nearly exactly:
for both studies reported in the paper, a random sample of the 2012 Cooperative Campaign Analysis Project
(CCAP) form the baseline data and normally distributed noise are added to simulate follow-up waves.


LaCour and Green (2014, Science) report a remarkable result: a ~20-minute conversation with a gay canvasser
produces large positive shifts in feelings towards gay people that persist for over a year. The study’s design is
also notable: over 12% of voters invited to participate in the ostensibly unrelated survey that formed the
study’s measurement apparatus agreed to be surveyed; nearly 90% were successfully reinterviewed; and each
voter referred an average of 1.33 other voters to be part of the study who lived in the study area.

The changes in respondents’ feeling thermometer scores are perfectly normally distributed. Not one
respondent out of thousands provided a response that meaningfully deviated from this distribution

All the above patterns can be explained by an extremely simple data generating process with the 2012
Cooperative Campaign Analysis Project (CCAP) data as its starting point.