Eye for an Eye: Psychology’s Sznycer and Wee publish work on laws about bodily damage

Friday, March 28, 2025

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Oklahoma State University Department of Psychology assistant professor Dr. Daniel Sznycer and experimental psychology Ph.D. student Yunsuh Nike Wee recently published research on the origin of laws about bodily damage.

Along with their colleague, Dr. Jaimie Arona Krems, associate professor of psychology at the University of California-Los Angeles, the researchers wrote the following article about their work. A version of this story was originally published on The Conversation in January 2025.  

Eye for Eye, Tooth for Tooth: What’s the Origin of Laws about Bodily Damage? 

The Bible’s lex talionis, “Eye for eye, tooth for tooth, hand for hand, foot for foot” (Exodus 21:24), has captured the human imagination for millennia. This idea served as a model for ensuring justice when bodily harm was inflicted. But where did such laws originate? A recent study by Yunsuh Nike Wee, Daniel Sznycer and Jaimie Arona Krems sheds light on this question, revealing links between laws about bodily damage and shared intuitions about the value of body parts.

Cultural Construction vs. Universal Valuation

According to a prominent theory, laws are cultural constructions. This “cultural construction” theory proposes that laws vary across cultures and historical periods, adapting to local customs and social practices. By this logic, laws about bodily damage would differ substantially between cultures.

However, Wee, Sznycer and Krems' study published in Science Advances journal — “Laws about bodily damage originate from shared intuitions about the value of body parts” — explores a different theory: that laws about bodily damage are rooted in universal human nature. On this view, different body parts are seen as having different values; people across cultures and throughout history agree on which body parts are more (or less) valuable; and these human intuitions about the value of body parts underpin laws about bodily damage.

This new theory begins with a simple observation: different body parts and functions have different effects on the odds that a human will survive and thrive. Life without a toe is a nuisance, but life without the head is impossible. This observation prompts a question: Might people intuitively understand that different body parts are differently valuable?

Knowing the value of body parts gives you an edge. For example, if you or a loved one has suffered multiple injuries, the most valuable body part could be treated first, or a greater share of (limited) resources could be allocated to its treatment. This same knowledge could also play a role in negotiations when one person has injured another. When person A injures person B, B (or B’s family) can, and often does, claim compensation from A (or A’s family). This practice appears around the world: among the Mesopotamians, the Chinese during the Tang dynasty, the Enga of Papua New Guinea, the Nuer of Sudan, the Montenegrins, and many others. It is known as wergild or “man price.”

But how much compensation is fair? Underclaiming leads to loss, while overclaiming risks retaliation. To walk the fine line between underclaiming and overclaiming, victims must claim compensation in Goldilocks fashion: just right — based on the consensus value that victims, offenders and third parties in the community attach to the body part in question.

This Goldilocks principle is readily apparent in the exact proportionality of the lex talionis, “eye for eye, tooth for tooth.” Other legal codes dictate precise values of different body parts but do so in money or other goods. For example, the Code of Ur-Nammu, written 4,100 years ago in ancient Nippur (present-day Iraq), states that a man must pay 40 shekels of silver if he cuts off another man’s nose, but only 2 shekels if he knocks out another man’s tooth.

Finally, we could ask: If people do acquire intuitive knowledge of the values of different body parts, might this knowledge underpin laws about bodily damage across cultures and historical eras?

Thanks to the work of linguists, historians, archaeologists, and anthropologists, we know a lot about how different body parts are appraised in societies both small and large, from ancient times to the present day. However, systematic tests of whether body parts are valued similarly across space, time, and levels of legal expertise (e.g., laypeople vs. lawmakers) hadn’t been conducted previously. This new research by Wee, Sznycer and Krem was designed to test that.

Testing the Hypothesis: A Cross-Cultural and Historical Examination

To test this hypothesis, Wee, Sznycer and Krems conducted a study involving 614 people from the United States and India. The participants read scenarios involving various body parts, such as “one arm,” “one foot,” “the nose,” “one eye,” and “one molar tooth.” The researchers chose these body parts because they were featured in legal codes from five different cultures and historical periods: the Law of Æthelberht (Kent, England, 600 CE), the Guta lag (Gotland, Sweden, 1220 CE), and modern workers’ compensation laws from the United States, South Korea, and the United Arab Emirates.

To determine whether natural, untrained intuitions underpin laws, participants who had college training in medicine or law were removed from analyses, as the researchers’ theory was that knowledge about the value of body parts is a feature of human nature, present in virtually every human. While the participants did not see the monetary amounts specified in the legal codes for the various body parts, the researchers analyzed whether the participants’ intuitions matched the compensations established by law.

The findings were striking: The values placed on body parts by both laypeople and lawmakers showed strong consistency. The more American laypeople tend to value a given body part, the more this body part seemed valuable also to Indian laypeople, to American, Korean, and Emirati lawmakers, to King Æthelberht, and to the authors of the Guta lag. For example, laypeople and lawmakers across cultures and over millennia generally agree that the index finger is more valuable than the ring finger and that one eye is more valuable than one ear.

But do people value body parts accurately, in a way that corresponds with the actual functionality of those body parts? Data about this are not available, but there are some hints that, yes, people do. For example, laypeople and lawmakers regard the loss of a single part as less severe than the loss of multiples of that part. In addition, laypeople and lawmakers regard the loss of parts as less severe than the loss of the whole, such that the loss of a thumb is less severe than the loss of a hand, and the latter is less severe than the loss of an arm.

Additional evidence of accuracy can be gleaned from ancient laws. For example, linguist Lisi Oliver noted that in Barbarian Europe “wounds that may cause permanent incapacitation or disability are fined higher than those which may eventually heal.”

Although people generally agree in valuing some body parts more than others, some sensible differences are also likely to arise. For instance, sight would be more important for someone making a living as a hunter than as a shaman. The local environment and culture might also make a difference. For example, upper body strength could be particularly important in violent areas, where individuals need to defend themselves against attacks. More research is needed to investigate these differences.

Cultural Similarities and Differences in Morality and Law

Much of what counts as moral or immoral, legal or illegal, varies from place to place. Drinking alcohol, mixing meat and milk, and cousin marriage have been variously condemned or favored in different times and places.

But recent research has also shown that, in some domains, there is much more moral and legal consensus about what is wrong — across cultures and even across the millennia. Laws about bodily damage seem to fit into this latter category of moral or legal universals. Wrongdoing such as arson, theft, fraud, trespassing and disorderly conduct, also appears to engender a morality and related laws that are similar across times and places.

In this realm, one could say that the blueprint for the moral-legal structure of humanity as a whole is contained within individual human brains. For bodily damage and other types of wrongdoing, the proverbial solitary castaway on an island could produce a decent draft of all legal codes past and present. Because he has a human brain.

Read more about Wee, Sznycer and Krems' work on The Conversation and in the journal Science Advances.