Common Sense May Not Be Commonly Shared, Sociologists Find

Common sense might not be so common after all, new research has found.

What one person might consider common sense might be very different to someone else, a new study in the journal Proceedings of the National Academy of Sciences reveals.

Common sense—classified by the researchers as things we know to be true without really knowing why—is much more unique to individuals than we first thought.

"First, we talk about commonsensicality, which we define in a specific mathematical way, but intuitively captures how much agreement there is between people on a topic, and the extent to which individuals know what others think about that topic. In this way, more commonsensical things are things we all agree on and we all know we all agree on them," study author Mark Whiting, a senior computational social scientist at the University of Pennsylvania, told Newsweek.

"Second, we talk about collective common sense, which we define as groups of shared belief between people and topics. The idea of this measure is that it gives us a sense of how many things you are likely to believe in common with a group of people," he said.

If a group is small, say only one other person, you can probably find many things you both agree on, but as the group gets larger, the number of things you all agree on is proportionally much smaller and quickly becomes almost zero as the number of people increases.

"The first definition is a bit like saying how likely a claim is to be common sense, or how likely someone is to know something. The second definition is like thinking about what, if anything, everyone in the community actually thinks of as common sense, i.e., what are the things that we all know in common," he said.

This paper attempts to resolve the ambiguity of traditional definitions of common sense using an analytical framework, and figure out how common certain common sense beliefs are.

"The notion of common sense is invoked so frequently in contexts as diverse as everyday conversation, political debates, and evaluations of artificial intelligence that its meaning might be surmised to be unproblematic," the authors wrote in the paper.

"Surprisingly, however, neither the intrinsic properties of common sense knowledge (what makes a claim common-sensical) nor the degree to which it is shared by people (its 'commonness') have been characterized empirically."

The researchers—from the University of Pennsylvania—used a case study of 4,407 claims of common sense from several sources, and asked more than 2,000 people to rate how common-sensical each claim was.

These claims included things like "perception is the only source of knowledge, what is not perceived does not exist;" "rudeness is the weak man's imitation of strength;" "triangles have three sides;" "numbers don't lie, we should always trust the math;" "all human beings are created equal;" and "avoid close contact with people who are ill."

They found that between individuals, things considered to be common sense varied significantly across a variety of claims, and at the collective level, few claims matched the definition of common sense as being obvious to everyone.

"For the most part, individual demographics don't seem to predict levels of common sense, i.e., being older, better educated, more or less political etc, all don't seem to give people more common sense. In our data, the one thing that did appear to show a relationship is social perceptiveness—the more people understand what others are thinking the more they seem to have common sense," Whiting explained.

"On another level, people didn't seem to have predictably consistent ideas of what is common sense. This is why we get the result I mentioned above, where although two people might agree on many items, the number of items that a larger group all agree on is vanishingly small. In this way, effectively each person's common sense is close to unique to them, so as a consequence, common sense is not all that common."

The researchers hope that their analytical framework may be helpful in future studies involving social science and artificial intelligence.

"We anticipate that this tool will be used in larger-scale studies in the future, furthering our collective understanding of common sense and its role in both human and artificial intelligence," they wrote.

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Update 1/16/24, 09:42 a.m. ET: This story was updated with comments from Mark Whiting.