How Can You Tell If Your Lover Is Cheating?

In Carrie Underwood's song "Before He Cheats", she imagines her lover pursuing another woman in a bar and obviously trying to cheat on her. But often the evidence for cheating is less conclusive, and websites such as wikiHow provide lists of signs that your lover might be cheating. Unfaithful lovers might be overly protective of their phones or computers, diverge from their usual schedules, act more secretively, behave less affectionately, change their appearance, or accuse their partners of cheating. However, none of these is a sure sign of cheating, because they all have alternative explanations. For example, your lover might be protective of a phone because it was used to buy a secret gift for you. You need to be able to infer that your lover’s cheating is the best explanation of all the evidence.

This kind of inference to the best explanation is common in many other spheres of life.

• When a patient goes to a doctor and describe symptoms, the doctor forms a diagnosis concerning what disease or condition best explains the patient's symptoms. This diagnosis should fit with everything that the doctor knows about the patient's current condition and background history.
• When a car owner takes a vehicle in for repair because it is not working properly, the mechanic makes an inference that the car’s malfunction is the result of a particular breakdown in its parts.
• When a jury is presented with evidence in a criminal trial, the jury has the responsibility of deciding whether the accused is guilty or not, which requires evaluating all the evidence and figuring whether it is best explained by the hypothesis that the accused criminal really is guilty.
• When scientists are puzzled by experimental evidence, they try to find theories that provide the best explanation of the evidence, taking into account alternative explanations and overall compatibility with accepted scientific views.

In all of these cases, people make an inference to the best explanation of puzzling evidence, where the best explanation is evaluated by considering the overall fit of different hypotheses with all the evidence.

My theory of explanatory coherence was originally developed for thinking in science and law, but it applies equally well to everyday life. Here are the considerations that go into evaluating hypotheses such as that your lover is cheating.

1. How much evidence does the hypothesis explain? The case for cheating is stronger if there are many surprising behaviors that it might explain.

2. What are the other hypotheses that might explain this evidence? For example, your lover may be behaving differently because of pressures at work.

3. Does the hypothesis provide simple explanations that don't require a lot of extra assumptions? A complicated hypothesis that your lover is having an affair with a movie star and managing to cover up multiple trips to Hollywood would require more assumptions than just thinking that your lover is involved with a co-worker.

4. Is the hypothesis supported by analogies to previous explanations? If your lover is acting in ways similar to behaviors that marked a previous case of infidelity, then cheating becomes more plausible in the current case.

5. Is the hypothesis explained by deeper hypotheses that indicate why it might be true? For example, if you and your lover have been having emotional conflicts, then your lover might be motivated to mess around with someone else.

Making a good inference to the best explanation requires combining all of these considerations: evidence explained, alternative explanations, simplicity, analogy, and deeper explanations. A neural network program called ECHO shows how such a combination can work in domains such as epidemiology.

Scientists put all these factors together in deciding whether one theory is better than its alternatives, for example when Darwin argued that his theory of evolution by natural selection provides a better explanation of a wide array of evidence that the then-accepted view that species were separately created. Similarly, people can make good inferences about relationships by coming up with views that have a large amount of coherence with all of the available facts and alternative hypotheses. In both science and everyday life, we should be reluctant to reach surprising conclusions without careful consideration of all the factors that contribute to inference to the best explanation.