This thread reminds me of a rumour I heard when I first did work for IBM. The story went that they often arranged interviews in the period running up to lunch, and if the candidate looked promising, offer to stand them lunch in the company resturant prior to continuing in the afternoon. When sitting down to lunch, the candidate was watched to see if they used additional salt and pepper. If they did so without having tasted the food first to see if it actually needed it, this was considered a black mark, indicative of an impetuous and/or imprudent (sp?) personality.

Following lunch, the candidate would be informed that the company policy was for no alcohol on the premises, but that there was a sport club bar in the grounds where this rule was relaxed and was taken along to "see the facilities". Once there, the interviewer would ask the candidate what he would like to drink!

The "correct answer" -- fruit juice, a small beer, coffee or "Nothing thanks." -- varied depending upon the teller, but all choices had some significance and it wasn't always a "bad thing" to opt for the beer, or the safe bet to go for coffee.

I can see how the "left over" white board code could be construed into some kind of "psych test". And any response, could be a double-edged sword. You say something and you could be perceived as arrogant. You don't, timid or lacking confidence. You do, "Why was he nosing around the room". You don't, "Did he miss it?"

If I noticed, I might say something like. "Interesting. That's not the way I would have done it!" as a parting shot.

That is, if the idea that it might be some kind of "secret test" didn't cross my mind, because if it did, I am quite likely to react quite differently.

If I could confirm the idea that I was being "secretly evaluated", I might seriously question myself if this was a place that I wanted to work!

It's a bit like the old standby. "Why do you want to come to work for us?". The best answer in my opinion, whether as an interviewer or an intervieweé, is: "I'm not sure that I do yet. That's why we are interviewing each other isn't it?". Too smug?