Leadership

Why Man­hole Cov­ers Are Always Round 

Brain­teas­er in the Job Interview

26. August 2021
Why Manhole Covers Are Always Round

You are in a room with three light switches, each of which operates one of three light bulbs in the next room. You have to figure out which light switch operates which light bulb. At the beginning, all the lights are off and you can't see from one room to the other. You can inspect the next room only once. How do you find out which light switch belongs to which light bulb?

Well, good question. So, there you find yourself sitting in the job interview, supposed to shine with a clever answer. Knowing full well that you're being tested on whether you can keep a cool head in stressful situations and think creatively, logically and analytically all at the same time. In short, whether you have brains. But is that really a good question for a job interview? And is that how you find out?

Brainteaser in a job interview

This interview method uses so-called brainteasers. For example, another classic is "Why are all manhole covers round?" Solution: "It's the only shape that can't accidentally fall through the opening." Tricky questions like these are designed to draw applicants out of their shells and, more importantly, out of their comfort zones. They aim to reveal desired characteristics such as problem-solving skills or perceptiveness. These are much more difficult to teach than (company-) specific technical knowledge. Among other things, brainteasers have become known through their use by tech giants in Silicon Valley. For instance, the example above with the light switches is asked at LinkedIn.

Brainteasers are reminiscent of classic case studies, as they are often used in the selection process by management consultancies. However, they are much shorter. And above all: much more unrelated. While case studies outline scenarios that are likely to be encountered later in everyday working life, hardly any applicant will ever deal with the question of how to get the giraffe into the refrigerator.

But what do you do if you suddenly have to estimate how many golf balls fit into a Boeing 747? (These are called Fermi questions).
First of all, take a deep breath and stay calm. It's usually not about the perfect answer, but the way to get there – how a problem is solved, not if. Therefore, don't immediately throw in the towel and stammer "I don't know" with a shrug. And don't guess either. Better ask questions to generate more information and then hypothesize or break down the main problem into several subtasks. Think out loud to reveal your approach, which is what it's all about.

What's the use of brainteasers?

Brainteasers mainly cause stress, confusion and a negative attitude within the applicants. A genius like Elon Musk can be forgiven for wanting to find employees at eye level in this way. But generally, they have a bitter aftertaste. Researchers have also found that brainteasers are usually not a suitable tool for revealing job-relevant skills in applicants. Rather, they reflect the personality of the questioner – in particular, HR professionals with narcissistic as well as sadistic personality traits tend to use brainteasers.

Better than brainteasers: structured interviews

The bad news: There will always be recruiters who want to lead applicants up the garden path.
The good news: The trend is moving in a different direction. Even Google, for instance, has admitted that brainteasers are simply a waste of time. According to Global Staffing Lead and Senior Recruiter Lisa Haynes, Google is now using structured interviewing methods to recruit the best talent. This involves asking all applicants for a position the same questions, as well as scoring their answers in the same way. The questions should be equally behavioral and situational. Behavioral questions are based on experience in the applicant's previous career. The classic: "Describe a situation in which you faced a problem. How did you solve the problem?" They are good indicators of how a person will behave in a similar situation in the future. Situational questions are hypothetical in nature and outline various scenarios. For example, "Imagine XY happens. How do you handle it?" That way, you learn something about the applicant's perceptiveness as well as their approach. With a balanced mix of these question categories, you have a good interview base.

Conclusion: It's better to grill sausages than applicants

The increasing competition for talent on the labor market puts organizations under pressure to find the best talents. If you treat potential employees poorly during the selection process, you quickly alienate them. What's more, it's easy for applicants these days to publicize inappropriate interview tactics on forums like Glassdoor. Worst case, you lose not only individuals, but entire talent pools. Image damage included. Therefore, don't grill your applicants, but rather (tofu) sausages. It's better for everyone.

Do you have experience with brainteasers in job interviews? Tell us about it via email or on our social media channels FacebookLinkedInXing or Instagram. We look forward to it!

Your Coopers Team

 

Solution:
Let's name light switches 1, 2 and 3.

Light switch 1 stays off.
Light switch 2 stays on for 10 minutes, then turns off.
Light switch 3 is turned on.

Now go to the next room. The light bulb that is off but still warm is switch 2, the one that is on is switch 3, and the cold one that is off is switch 1.

That's where the light comes on!

 

Photo by Johannes Plenio via Unsplash