Determining trademark infringement can often be challenging and fraught with controversy. The reason is that, at its core, a verdict for infringement requires proof that the two brands are confusingly similar. And yet the existing approach primarily relies on self-report, which is known to be vulnerable to biases and manipulation.

But this challenge also provides an interesting lens into the complex yet fascinating relationship between scientific evidence and legal practices. I am a marketing professor with a background in cognitive neuroscience, and one of my research interests is in using neuroscientific tools to study consumer behavior. In our recently published study, my colleagues and I demonstrated how looking directly into the brain may help solve the conundrum of how to measure similarity between trademarks.

Determining trademark infringement is messy

In most legal systems, trademark infringement decisions revolve around whether a “reasonable person” would find two trademarks similar enough to cause confusion. While this may sound straightforward and intuitive, judges have found it incredibly difficult to translate such a criterion into concrete guidance for legal decision-making. Many legal scholars have lamented the lack of a clear definition of a “reasonable person,” or what factors contribute to “similarity” and their relative importance.

This ambiguity is further compounded by the adversarial legal system in the U.S. and many other countries. In such a system, two opposing parties each hire their own attorneys and expert witnesses who present their own evidence. Often that evidence takes the form of consumer surveys conducted by an expert witness hired by a party, which can be susceptible to manipulation—for example, through the use of leading questions. Not surprisingly, plaintiffs are known to present surveys finding that two trademarks are similar, while defendants present competing surveys showing they are different.

This unfortunate situation arises largely because there is no legal gold standard about what types of background information survey respondents should receive, how the questions should be phrased and what criteria of “similarity” should be followed—all factors that can change the results substantially. For example, parties could include instructions on how respondents should evaluate similarity.

As a result, judges have developed some degree of cynicism. It is not uncommon that some simply discard the evidence from both sides and go with their own judgment—which could risk replacing one set of biases with another, despite their best intentions.

Asking the brain, not the person

Neuroscience may provide a way out of the dilemma: What if courts measured perceived similarity directly from the brain, instead of asking people to describe what they think?

To test this, we leveraged a well-known phenomenon of the brain called repetition suppression. When the brain sees or hears the same thing over and over again, its response to the repeated stimulus becomes weaker each time, as if it’s losing interest or doesn’t find the information as important.

Imagine you hear a really loud noise and your brain responds by triggering a fear response. But if you hear that same loud noise over and over again, your brain will start to get used to it and you won’t feel as scared anymore. This repetition suppression is thought to help the brain focus better on new or important information. Scientists have seen this happening in different parts of the brain, including those that process sight, sound, attention, and memory.

In our experiment, we rapidly showed participants pairs of images consisting of a target brand (such as “Reese’s”) and a supposed copycat (such as “Reese’s Sticks”) and used MRI scanners to examine activity in the part of the brain that processes visual objects.

Given repetition suppression, we would expect a maximum amount of response reduction if the second brand is exactly the same as the first one, minimum reduction if the two are completely different, and somewhere in between if they are somewhat similar. By measuring the degree of response reduction, we could then determine how similar, in the brain’s perspective, the two brands are.

This approach provides the important benefit of bypassing the need to ask people to judge how similar they find two brands, or defining what it means to be similar, which can be highly contentious in trademark lawsuits. A person might not even be conscious of the brain’s repetition suppression response.

Across the whole set of brands we tested, we compared the neuroimaging results against the results of surveys designed to favor the plaintiff, to favor the defendant, or to be more neutral. We found that the brain-based measure can reliably pick out the more neutral survey results, supporting the idea that brain scans could improve the quality of legal evidence in these cases.

Applying neuroscience to legal problems

It is crucial to note that looking into the brain doesn’t mean a legal decision automatically results from such data. Our method provides a better ruler to measure similarity, but it still falls on the judge to determine where to draw the line for infringement. Neuroimaging is also costlier than consumer surveys and can’t easily be done on as large a sample of people.

Interdisciplinary discussions and a better understanding of neuroimaging techniques are necessary before broader uses can be integrated into the legal system. The courts play a crucial role in deciding when new insights from neuroimaging should be considered in a case and how they should influence its outcome. Therefore, it is becoming increasingly important for judges and lawyers to have a working knowledge of neuroscientific techniques.

Our approach also opens the door to the possibility of applying neuroscience to a variety of legal cases centering on the “reasonable person,” such as copyright infringement, obscenity, and negligence. More broadly, it offers a novel perspective on the burgeoning field of neurolaw, which seeks to refine and reform legal thinking using insights from neuroscience.

Most existing work in law and neuroscience focuses on criminal culpability, or evaluating someone’s mental state while making a certain action. But little attention has been paid to seemingly more mundane questions in civil law that could arguably have an even broader impact on people’s everyday lives. We believe that broadening the ways neuroscience can contribute to the law could help improve legal decision-making.