Studies have shown that interviewers subconsciously decide whether to hire you within seconds of meeting you, and will spend the rest of the interview justifying in their mind the decision that they've already made. A study by Princeton psychologists Janine Willis and Alexander Todorov found it takes a tenth of a second to form an impression of a stranger, and any time after doesn't significantly alter their impressions.
This means that when an interviewer first meets you, they will decide very fast whether to hire you from what they see. These first impressions include race, clothing, hygiene, your handshake, and your voice. They may use predetermined impressions and stereotypes to unconsciously make assumptions about who you are, and whether they like you.
I'm a first semester senior in college right now, meaning I'm in the midst of a ton of job interviews. Sitting in the waiting room for an interview, I will grow increasingly self-conscious as I size up the other candidates. Typically, I'm one of the minority races, a small Asian female. Looking around the waiting room, I'll see a lot of taller, bigger, and stronger-looking candidates. The thought always crosses that if I were the recruiter, even I would pick the other candidates who just look like a stronger image.
I didn't want to believe it at first, but the more jobs I have and job interviews I do, the more I believe the strong weight that race has on a job decision. I recently noticed that on my resume, I have eight jobs listed under my experiences, and all of them involved either an Asian boss, Asian location, or several Asian co-workers. However, the vast majority of jobs I apply for have none of the above. The chances of this happening point to race being a more-than-significant factor in whether I get a job offer.
For the most part, recruiters likely don't even notice they place that much weight on first impressions and appearances. It's something built into our brains that we don't even realize. Not much can change in this arena from the recruiter side - for me, noticing this has heightened my attention on a first impression. Groom as best as I can, sit as tall as I can, smile and make the most eye-contact I can.