If IQ testing is illegal in US job interviews, why do software companies get away with it?

Ahm, it's not illegal to give an IQ test in a job interview.

Simple answer is that intelligence is not considered a protected class: http://en.wikipedia.org/wiki/Protected_class Which, if you spend two seconds to think about, makes total sense: companies have followed the ideal of hiring talent for a long time now, and intelligence correlates with talent just as well as any other positive work-related metric. As to your complaint about why software companies seem to be testing for smart engineers (and I'll reiterate, these are not formal IQ tests) when most programming is routine, you'd be surprised at the range of programming talent and therefore why we need to hire the best people. I've seen people struggle at interviews defining basic concepts, parsing simple algorithms, coding a trivial solution in their language of choice, etc. - stuff that you would run into a few times a week in your routine programming job. In that light, the definition of "routine" depends largely on whoever's defining it.

It's not illegal, but you can get into trouble if the IQ test is not "professionally developed" or if the results are misinterpreted or applied in an illegally discriminatory way. See http://www.personalityplus.net/is-employment-testing-legal.htm for some links. While it is true that most programming activities don't require a lot of brainpower, most programmers do run into hard problems once in a while, and one could expect that smarter programmers get things done faster and produce fewer bugs, so it is not unreasonable for employers to prefer hiring smart people over not-so-smart people. Why do they get away with it? Because not enough people are suing them and winning. I personally think that interviewers who ask lots of puzzle questions are idiots, but I don't think it's illegal.

I am not a a lawyer. I am not your lawyer. So despite what the badly informed people are saying my research concludes that yes its illegal per Griggs v. Duke Power Co.: http://en.wikipedia.org/wiki/Griggs_v._Duke_Power_Co. They are illegal due to the bias generated from the results, and because the people who make the tests cannot help but put their own biases in the test. Thus, a test created by a white person may actively discriminant against blacks, etc, due to cultural differences.  This is not always the case of course, but the ruling I found states they the generally agreed on definition is true enough that due to that ruling and others its actively illegal at the federal level to put somebody through a IQ test on a job interview because they can easily go after your company at the federal level if you do so. To quote the law/ruling: "Good intent or absence of discriminatory intent does not redeem employment procedures or testing mechanisms that operate as 'built-in headwinds' for minority groups" - Warren Burger, Chief Justice. To get around this, most companies do what we calla "skill assessment" to get around the law.  Simply put. they ask you to do something that could hypothetically work related but statistically you would never have to actually do and then grade you on how you came to the answer, hopefully knowing the answer themselves far in advance so that they have this capacity and can do so with accuracy.

Besides what everyone else has said, I would say that it's because your ability to think logically and use logic in your work has a strong correlation with programming (because code is basically a lot of logically organized, coherent  instructions). Since IQ tests measure logic, then they would be useful indicators to predict programming skill.

One additional thing worth pointing out is that while the requirement of a test may be determined to be illegal however individual voluntarily taking a test does not violate the law.

It is not illegal to give an IQ test as part of a job interview in the U.S.; however, that test must be given by a licensed psychologist, and there are very few who would likely be willing to stake their licensure on using IQ tests in these ways. The publishers of IQ tests in the U.S. do not want their tests used that often, or for those purposes, however, so anyone caught doing that could have their privileges affected and a person could make a complaint to the licensing board in that state.Corporations typically never give IQ testing per se, but they may give tests of "achievement." They are not necessarily testing IQ (or, native intellectual abiliites), but they can test your basic knowledge in many areas, including tests of cognitive and problem solving skills.