I wonder whether this study really shows what people are inferring from it. Aside from the somewhat unreliable metrics ("not happy" contains happy => positive!)

I wonder whether this study really shows what people are inferring from it. Aside from the somewhat unreliable metrics ("not happy" contains happy => positive!), an increase in negative posts when being shown negative posts could subconsciously promote Facebook as a place to vent, etc. I'm sure the study addresses these things, but as usual the summary is "Seeing unhappy things on Facebook makes people unhappy!"