Which two cultures are most dissimilar?

49 characteristics describe our world

Whether fluffy, colorful or valuable: our brain needs surprisingly few features to clearly recognize a chair, a dog or any other object in our environment. Just 49 characteristics are enough to categorize almost anything, as a study has now revealed. The spectrum ranges from properties such as color, shape and size to attributes such as “can move” or “has something to do with fire”.

How do we recognize a pizza, a rocket or a bird? At first glance it seems simple, because all of these things have certain salient features: a bird has feathers and wings, a rocket is elongated and has fire-breathing nozzles, and a pizza is flat, round and topped. For categorization, our brain breaks down the objects into individual properties and uses this combination to compare them with mental categories.

Which object doesn’t fit?

But which and how many features are based on this internal inventory? Martin Hebart from the National Institute of Mental Health in Bethesda and his colleagues have now examined this in the most extensive study to date. To do this, they showed almost 5,500 test persons different combinations of three objects and asked them to name the object that was most dissimilar to the other two.

“From this it can be deduced what is perceived as particularly similar and what is particularly typical for a category,” explains Hebart. With a total of 1.5 million three-way combinations and the decisions made by their test subjects, the researchers were able to determine the characteristics according to which people categorize and group things.

The highlight: It is precisely the individual differences that best reveal which properties are relevant. In the case of koalas, pretzels and carpets, for example, one person can sort out the koala as the most dissimilar, because it is the only one that is an animal and thus animate. However, another person chooses the pretzel as dissimilar because carpet and koala are both fluffy. This shows that both “animal” and “fluffy” can be relevant characteristics.

49 characteristics - from round to "something with water"

The result: our brain only needs 49 features to recognize and categorize almost any object. “Our results show how few properties are actually needed to characterize all objects in our environment,” says Hebart. As the tests showed, only nine to 15 of these object dimensions are often sufficient for identifying “things that do not fit”.

The 49 relevant characteristics include descriptive properties such as round, colored, small or large, but also overarching categorizations such as function, belonging to a group of organisms or value. Also included is, for example, whether a thing consists of one large or many small, similar sub-objects - like a plate of spaghetti.

Insight into the basic principles of our thinking

"Basically, we are explaining the basic principles of our thinking when it comes to objects," says Hebart. But there are also many new questions that can now be investigated using similar approaches. For example, it is unclear whether the relevant object dimensions are the same for all people: “How are they influenced by gender, age, culture, education and other socio-demographic factors?” The researchers ask. And what role does the person's familiarity with the objects in question play?

At the same time, the results also shed light on certain neurological phenomena: it was previously believed, for example, that patients who were unable to identify certain animals because of brain damage did not recognize living beings as a whole. It is possible that the person concerned has a deficit in recognizing the “fluffy” quality that underlies the animals. Other forms of therapy may then be derived from this. (Nature Human Behavior, 2020; doi: 10.1038 / s41562-020-00951-3)

Source: Max Planck Institute for Human Cognitive and Brain Sciences

19th October 2020

- Nadja Podbregar