How Partners Know Whether They Can Trust Each Other

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In a solid relationship, both partners don't lie, cheat, or otherwise violate the underlying set of premises that allow them to trust each other. Like the bedrock on which a building sits, this foundation of trust makes it possible for you to share completely your worries, doubts, and fears as well as your hopes, dreams, and aspirations. You don’t have to worry that your partner will use this information against you in any sort of manipulative way.

What happens when your partner doesn’t share your deep sense of commitment to openness and honesty? Perhaps you’ve caught your partner engaging in a behavior that violates a longstanding agreement. Your partner told you that they needed to go for a walk to get some fresh air, but when they come back, you smell smoke on their clothes. Given that your partner told you some months ago that they had given up cigarettes, you start to wonder what else your partner might be hiding from you.

According to Texas A&M International University’s Mónica E. Muñoz and Sissy De Los Reyes (2021), the people most likely to engage in such acts of relationship dishonesty tend to be dishonest not just with their partners. These are the individuals also most likely to be characterized by the dark triad traits of Machiavellianism, psychopathy, and narcissism. Personality psychologists coined this term after discovering that these three undesirable attributes tend to cling together when researchers try to understand the organization of traits within people’s psyches.

Why Are Dark Triad Partners so Bad for You?

It’s bad enough to be high on Machiavellianism, the tendency to try to exploit and manipulate others. When you add psychopathy, the factor that incorporates lack of empathy, and narcissism, or extreme grandiosity, you can see that these qualities could contribute to a partner’s tendency to distort the truth. Presumably, you would have already detected something amiss in terms of your partner’s reliability by now, but because individuals high in these traits are so good at deception, the clues might never have manifested themselves.

Indeed, as Muñoz and De Los Reyes point out, people high in the dark triad traits engage not only in deception with their partners, including infidelity, but also try to coerce their partners, feel a lack of commitment, view “love as a game,” and have an avoidant attachment style meaning that they chronically resist closeness. You could fall in love with one of these individuals regardless of these potentially toxic qualities because they are so good at drawing you into their world, at least at first. However, “the strict honesty expectations of committed relationships may thwart them.” If that relationship does persist, those high in these qualities will “perceive an increased need for deception.”

How Relationship Rules Operate When Partners Are Honest with Each Other

The need to deceive their partners as time goes by completely goes against the ordinary “relationship rules” in which partners who are committed to each other agree to abide by the norms of honesty. These are the rules that Muñoz and De Los Reyes refer to as “obligatory.” In contrast, “discretionary” rules “allow flexibility to judge when deception is fitting.” People high in dark triad traits, the A&M authors propose, should be less likely to follow obligatory and more likely to follow discretionary rules when it comes to opening up to their partners.

Because both sets of rules can operate simultaneously, it’s even easier for a dark triad partner to get away with a prolonged pattern of deceptive behavior that you are unable to see through. Your partner could theoretically be honest enough of the time, following the discretionary rules, so that you don’t spot the lies when they occur. That cigarette situation fits into this category.

Most of the time your partner doesn’t violate the no-smoking policy in your relationship, or at least, most of the time it’s not that obvious to you. Similarly, your partner could be honest about a range of other behaviors when there’s no reason to lie. As a result, you’ve got no reason to be suspicious and assume both of you are operating by the same set of relationship rules.

Putting the Dark Triad and Relationship Rules to the Test

In keeping with this general framework, Muñoz and De Los Reyes hypothesized that people high in dark triad traits would show greater adherence to discretionary and less to obligatory relationship rules. The sample on which they tested this hypothesis included 257 undergraduates, primarily female, and ranging in age from 18 to 29; almost all described themselves as Hispanic.

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You can see how you would score on the dark triad measures the participants completed by rating yourself on these sample items:

Narcissism: “I insist on getting the respect I deserve.”

Machiavellianism: “Most people can be manipulated.”

Psychopathy: “I’ll say anything to get what I want.”

The authors measured adherence to relationship rules with items such as these:

Obligatory: “My partner should never lie to me under any circumstances.”

Discretionary: “My partner and I can keep secrets from each other.”

Turning now to the results, it appeared that breaking the dark triad into its component parts was important in understanding who would be most likely to deceive their partners. The narcissism scale used in this study showed no relationship to either set of rules; instead, psychopathy stood out as positively related to discretionary and negatively related to obligatory rules. People high in Machiavellianism were also likely to adopt discretionary rules of honesty.

The study’s findings support the hypothesis that there is a carryover of personality traits into relationship behaviors involving deception. Although narcissism didn’t prove to be a significant predictor of relationship rules, the authors noted that the scale itself had limitations from a statistical point of view.

You may be wondering whether the results would be different if the participants were older, included more males, and were involved in long-term relationships. The idea that discretionary rules start to evolve in dark triad individuals over time could therefore be more realistically tested. As a preliminary test of the hypothesis, though, the findings suggest that this area of research could prove useful in understanding what can go wrong when people get involved with partners who regard the “truth” as a negotiable entity.

What to Do If Your Partner Won’t Abide by the Rules of Honesty

You may already be quite convinced that your partner is following a set of rules different from your own. Perhaps it’s not just one instance, such as that cigarette situation, but many others that are almost so undetectable that they fall below your radar. When you stop and think, you realize that they all add up in a way that can seriously undermine your relationship.

All of this is premised on the assumption that you are committed to the relationship and want it to endure, despite your partner’s tendency to view truth as relative. You’re still attracted to your partner, feel that you are in it for the long haul, and share many other values and goals. If it's true, as the Texas A&M authors propose, that people high in dark triad traits are “thwarted” by demands for honesty in long-term relationships, this could mean that they themselves want to stay in the relationship but perhaps don’t actually know how to be honest.

If deception has become a way of life for your partner, perhaps they need to be shown that it’s okay to tell the truth, even if the truth is bad. The reason your partner snuck out to get a cigarette is due to fear of reprisals from you for breaking an agreement not to smoke. Showing that you understand your partner’s difficulty in giving up the habit can allow you and your partner to work through this together.

To sum up, if your partner’s dark triad traits seem to undercut the very basis for your relationship, by making the rules for honesty explicit, you may be able to open up new lines of communication that can ultimately build the trust needed as you navigate the years ahead.

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