I have hooked up with other people when I was in a committed relationship.

These were the traits with the most significant correlations.

(*significance alpha = .05 > .07 correlation, sample size 1500)

Selfishness, physical attractiveness, substance abuse, lack of ethics, lack of impulse control, sexual addiction, among other traits all make it more likely that one has cheated.   Men are only slightly more likely to cheat than women (or admit to it on an anonymous test) based on this data.    Selfish men are more likely to self rate as cheaters than selfish women possibly because selfish women perceive that it might not be in their self interest to cheat.   Women are more likely than men to be financially dependent on their partner so relationship dissolution is a greater liability.

Unethical women are more likely to self rate as having cheated.  This gender divide may be explained by women being more picky in mates than men.  Men will hook up with unethical women, women may be less likely to hook up with unethical men.  The same phenomena may explain the gender difference in the Discreet trait scores.

Domineering, Materialistic, and Actor high scoring men also are more likely to cheat than similar high scoring women.  Need to Dominate and Materialism differences may be explained by those traits being more attractive to women than they are to men.

The big five/sloan profile is a little different for each gender.   Selfishness and lack of curiosity defines the male cheater.  Low curiosity makes sense from the standpoint that a non introspective person is less likely to consider / think about whether his behavior is harmful to others.   Socialness and Selfishness define the unfaithful female.  Social females are exposed to more opportunity to cheat than less social females and even social males (since women are pickier than men).

The second infidelity item was:

I have carried on romantic affairs while I was in a committed relationship.

One time cheating could be considered a smaller offense than partaking in an ongoing affair.  So I was curious to see whether the above item showed a different pattern than the first.   The average score was pretty much the same, slightly lower.

The correlations were pretty much the same suggesting that the personality of someone who cheats on occasion is not really that different from the personality of someone who would carry on an ongoing affair.   The small differences that exist appear to be related to impulse control.   Low Fiscal Acumen is related to having low impulse control, and it appears that one time cheating is more likely to happen in impulsive types than ongoing affairs.

The big five/sloan profile is also the same on this item.

Wrapping up, if you're partner is any of the following - physically attractive (Self Image), really likes to drink and/or smoke (Hedonism), cares a lot about looks (Vanity), can't manage money well (low Fiscal Acumen), is unethical, really likes sex, is selfish (low Accommodation), is not reliable (low Honor),  is argumentitive (Conflict Seeking), is untrustworthy (low Discreet), really cares about money (Materialism) - they are more likely to self rate as being unfaithful.

To add some more context, I took all users who scored very high on the Self Image trait (HSI) to see their average on the above two items.  (*scoring scale is 1-5 | very inaccurate - very accurate)

As you can see the difference is significant.  Here are the averages of users who scored very high on the Vanity trait (HVa).