Essential or Incidental?

I have a friend who decided a while ago that she doesn't want kids. She's got pretty sound reasons for not wanting to procreate, and she's always seemed happy with that decision. But recently she told me that she felt a pang of doubt when she saw a family sitting out on their patio, barbecuing and looking really cozy and happy together.

She confessed to me, "Now I'm starting to worry that I could be making the wrong choice, because I found the idea of being in that scene so appealing." My response: "Okay, imagine that same scene again, but instead of being there surrounded by your hypothetical children and husband, you're surrounded by your close friends. Now how do you feel about it?" She replied, "Oh. Actually, that feels just as good."

The thought experiment had revealed that she was reacting positively to the "Idyllic afternoon in the company of people you love" aspect of the scene, not specifically to the "Idyllic afternoon in the company of family" aspect. The latter is a subset of the former, of course, but she had erroneously assumed that the "family" component was a necessary condition of the scene's appeal to her, when in fact it was incidental. And it only became clear which components were necessary, and which incidental, by isolating them via thought experiment.

What I thought was interesting about this case is that it was a real-life occurrence of a problem researchers face all the time: you observe a phenomenon with a bunch of attributes -- say, A, B, and C -- and it's not clear which attributes are essential to the phenomenon, and which are irrelevant. Is A necessary and sufficient to produce the phenomenon, with B and C being totally irrelevant? Is the interaction between A and B the necessary cause? Would any one of the three attributes on its own be sufficient?

For example, if you observe that vegans tend to live longer than average, is that effect due to the lack of meat in their diets? The lack of all animal products? The higher amounts of plants in their diets? Is their veganism in itself completely irrelevant and merely correlated with some other feature that's responsible for the benefit, like higher levels of exercise? Or maybe the increased lifespan is caused by the combination of more plants and more exercise, and neither factor would be sufficient on its own?

If you're attuned to this problem of ambiguous causality, as good researchers usually are, you can try to isolate potential causes and study how the outcome changes when you change one factor at a time. But in your daily life, it's much easier to jump to conclusions without even realizing you're doing so, like my friend did.

The happy-family case study deserves particular mention, I think, because it's a special case of ambiguous causality, in which you form an overly-specific hypothesis instead of the correct, more general one. I touched on this phenomenon in an earlier post, in which I described a study where people were given the series of numbers "2, 4, 6" and asked to guess the rule that those numbers were following. Most people hypothesized something like "increasing even numbers" or "increasing by intervals of two", when in fact the correct rule was simply "increasing numbers." The evenness, and the intervals of two, were both incidental, the same way the family-ness of the scene my friend observed was incidental to the feelings it induced in her.

For a less contrived example, consider acupuncture. People found that sticking needles in specific "pressure points" prescribed by traditional Chinese medicinal theory helped alleviate pain, and they took that as validation of the pressure point theory. But when researchers tried sticking needles in other locations on subjects' bodies, they got the same effect. As far as science has been able to tell so far, the "pressure points" were incidental to the pain relief; the "sticking with needles" was the only essential component.

I have a suspicion that this fallacy might also come into play when people consider the effect of religion in their life. I've heard people describe how belonging to their church makes them happier, or makes them better people. But is the religiousness of the community essential to its beneficial effect? Or would any tight-knit community produce the same result? It's not necessarily obvious until you experiment with removing the component you thought was crucial -- although fortunately, as in the case with my friend, sometimes a thought experiment does the trick, and you can disentangle essential from incidental from the comfort of your armchair.

I got all excited when I couldn't find this phenomenon described on Fallacy Files, because one of my life goals is to discover a new fallacy or bias and get the privilege of picking its official name. But after I'd already daydreamed about what I was going to call it, I did a little more googling and discovered it might actually fall under the heading of an obscure fallacy that's already been coined: "Confusion of Essence and Accident," in which you "assume that some accidental feature or property of something essentially belongs to it." Alas, it looks like the world might have to wait a little longer before "Julia Galef's Totally Brilliant New Fallacy" is added to to the logic textbooks.