As folks pointed out, the article doesn't actually list any sources (unless you count name-dropping the one scientist). Not to mention the OP (and the article's actual headline) misrepresented what the article actually says. The first impression is important, but it is not set in stone.
In the example given, a person has 'unfavorable impressions' of his co-worker. Maybe the co-worker seems grim, dour, overly serious, whatever. Then he meets this co-worker at a party, and the guy's loosened up, having fun, is a nice guy, etc. In this new context, the observer sees that his first impression was wrong - but in other contexts he'll assume the original impression was more accurate, which actually makes a fair bit of sense.
Eventually, despite that bad first impression, if people get to know you in a variety of different contexts, they'll have favorable impressions for those. I actually find that kind of heartening.
It's easy to think that our stupid monkey brains make us all jerks, and to a degree that's true. But as the article says, this is a 'gut response' - not a guarantee.