Studies of human beings by sociobiologists say that humans tell the truth mostly when it suits their interests. Most people tell several lies every day, whether you call that shading the truth, omitting it, or altering the facts to suit a more favorable outcome for the teller.

A recent study found teenagers, for example, routinely telling 10-20 lies a day.

Our biological makeup is designed to increase our survivability, meaning inclusive fitness with our group. Studies show people persistently find their group (meaning team, nation, company and so forth) to be the 'good' guys while the other group in competition to be the bad guys. The end result is that you don't even see violations or misdeeds by your group while calling foul on the other guy. You can see this process in national politics, in racial strife, team sports, just about anywhere there are two or more people interacting competitively.

We have objective means to measure the truth. If there's a red apple on my desk, and I call it an orange, then either I'm irrational, lying or maybe color blind with bad eyesight.

My take: it's in my self-interest to tell the truth consistently as it leads to better outcomes with my group and anyone I do business with, however, I am not above shading the truth or omitting or withholding the truth in my self-interest. I believe the same is true for everyone but the actual behavior may vary widely from person to person between very truthful to very deceiful.

I'm aware my biology will persistently bias my perceptions in my favor, and that this is the same for everyone. Also, that I have no way of detecting the 'truthfulness' of another person except through their consistent behavior over time. While I think of myself as a honest person, I'm not above lying if the stakes are high enough (personal survival for example). I also think that's true of everyone.