Learn how to avoid interview bias.

First impressions, according to a recent Psychology Today article, are correct only about 30 percent of the time.

They should never, of course, be the basis for a hiring decision; however, research has shown bias can — perhaps subconsciously — affect the process of interviewing candidates.

A study, for example, involving mock employers interviewing candidates who were introduced both with and without theatrical prostheses that made them appear to be obese identified an interview bias against overweight job candidates — particularly if they’re female.

Another study, published in the Journal of Applied Psychology, found taller job candidates may receive preferential treatment in the workplace. An inch of height can equate to nearly $800 in additional salary, according to the study’s results, netting employees who are 6 feet tall almost $166,000 more during their career than someone who is 5’5”.

Identifying a candidate as more qualified because he’s tall or thin isn’t always a deliberate decision; the assessment may occur due to the interviewer’s perception of various physical traits, which has likely been determined by decades of independent experiences and varying amounts of influence from outside sources.

However, even if interview bias isn’t a conscious effort, the result can be damaging.

A 2015 study conducted by researchers from Rutgers University in New Jersey, the Department of Organizational Behavior at the University of Lausanne in Switzerland and the Department of Psychology at Kennesaw State University in Georgia determined bias can have a detrimental effect on the overall process of interviewing candidates — and a job candidate’s performance.

In the study, interviews conducted by men with a strong implicit bias resulted in both lower interviewer evaluations and lower self-evaluations by the applicant.

To reduce the effect of interview bias, the study’s researchers suggested several strategies, including offering training to help remove implicit interview bias and examining ways interviewers can tweak their nonverbal behaviors when interviewing candidates.

Other strategies to prevent interview bias include:

Utilize teamwork. Having more than one or two company representatives involved in interviewing candidates can help provide a more balanced take on the applicants’ capabilities. Employers conduct, on average, three phone and three in-person interviews, according to a CareerBuilder survey; for 36 percent of U.S. job candidates, the process typically involves meeting with multiple people within a company.

Multiple-employee interviews are about as common in France, Canada and Germany, where 36 percent, 34 percent and 41 percent of interviewing candidates meet with more than one person.

Use behavioral interviewing techniques. Research — specifically, a 2002 study on reducing gender stereotypes’ effect on performance evaluations — has shown that using a structured system, based on observed behaviors, instead of judgments, to rate employees can result in more accurate assessments.

Designed to elicit responses that provide insight into a job candidate’s strengths and weaknesses, behavioral interview questions are a strong way to determine if a candidate is a good fit — and they can help interviewers avoid subtle interview bias influences.

Instead of asking the traditional questions, when interviewing candidates, focus on finding out about deliverables the person has produced, such as an example of how she dealt with a work challenge or designed a production schedule for a project. You’ll get more information from that type of response than you will from a question about what the person studied in school. If you’re not sure what to ask, peruse our blog post on the three behavioral questions you should consider asking job candidates.

Remember that job candidates who sell themselves well aren’t necessarily the best fit. Managers — of both genders — are twice as likely to hire a man as a woman for a mathematical position, according to a 2013 study, which also found men are more likely to tout their talents during interviews, while women generally downplay them.

Ask job candidates to provide statistics, sales numbers, references and any other data to support their statements. The study also found providing objective performance information to interviewers helped give female candidates a better chance to obtain a position.

Implementing steps and processes to prevent first impressions from causing a degree of unconscious bias when interviewing candidates, ultimately affecting hiring decisions, should be an ongoing, enterprise-wide effort.

To start an internal conversation about gender-related interview bias, consider encouraging HR professionals and company leadership to take the free Implicit Association Test, created by group of researchers from Harvard University, the University of Virginia and the University of Washington.

The online test can help determine if respondents mentally connect career- and family-related terms to a specific gender — and takes less than 10 minutes to complete.