Although I was unable to access the full article, the framing from the abstract seems to be: "Which is less human?" Followed be two pictures of cyclists. The question frames dehumanization as a given. I do not specialize in crafting these kinds of surveys, but it seems like "people dehumanize cyclists" is a weird conclusion to draw. I don't know what the pictures were or if they were in color or silhouette, but I can imagine people are not used to seeing cyclists in safety vests and therefore it's rated as least human, because it's the least often seen kind of person riding a bike (at least in my experience). Just a friendly reminder to always look at the source, especially if it's so easily accessed, since the commenter above was kind enough to link directly.