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Filling in the Gaps: Biases and Pareidolia

April 17, 2026

Our brains are amazing, allowing us to do so much. Even so, they aren’t perfect. Do you remember during COVID, you would meet people for the first time wearing masks? Then, when you finally saw their whole face, you were surprised. And it’s not like you had purposefully thought about what the bottom half of their face looked like, but it was still somehow different than expected.

Facial Recognition & Pareidolia

This may be due in part to the fact that humans are wired to recognize faces. This is such a strong skill that we even recognize “faces” in inanimate objects: the front of cars, electrical outlets, even clouds or rocks. This phenomenon is called pareidolia, a human tendency to recognize meaningful patterns, especially faces. This is thought to evolve from the need to quickly recognize facial expressions for threats or social cues. We even have an entire region of the brain responsible: the face fusiform area (FFA) (Zhou & Meng, 2020). Studies have shown that even infants can recognize face-like patterns as faces (Kato & Megitani, 2015). Infants as young as seven months were able to recognize faces in Arcimboldo’s paintings (Kobayashi et al., 2012). These paintings were of inanimate objects, such as vegetables, arranged to resemble a portrait of a human. They are honestly a bit creepy, but feel free to give it a google!

Obviously we can all recognize a face, even under a mask, but a study using an artificial face recognition system gave us some evidence for why. A system called deep convolutional neural networks, or DCNN, determined the most important facial feature for facial recognition to be the eyebrows. This was followed by the eyes, mouth, then nose (Zhang et al., 2024). This makes sense with facial recognition under a mask, as the two most important features are still visible. Why the eyebrows are the most important isn’t clear. It could be that eyebrows are important for facial expressions, or that they are important for individual recognition due to their large diversity in color, shape, and placement.

Cognitive Dissonance & Bias

I found the science behind facial recognition fascinating, but it still doesn’t quite explain why we subconsciously fill in the bottom half of someone’s face. As it turns out, recognizing parts of a meaningful pattern, such as the face, but missing key parts of it, creates cognitive dissonance. Cognitive dissonance is when there is discrepancy between what your brain expects or believes and the information it is gathering. In the case of a mask, your brain is expecting to see all the important components of a face, so when the mouth and nose are missing, it creates a sort of tension. To relieve this tension, your brain uses what it knows about the face to fill in the gaps. This way, the pattern fits in with the categories we already have.

Significance

Pattern recognition, especially facial recognition, is super important, allowing us to recognize slight changes in facial expression or obstructed faces, like under a mask. But this can also lead to something not so great. Amy E. Herman said in her book “Visual Intelligence” that humans see through the brain, not the eyes. All your sensory organs collect signals and send them to the brain for processing. The signals don’t mean anything on their own, whether that is light through the eyes or smell through the nose. It is the processing that allows us to process these signals into something meaningful. This information is then tried to fit in with our prior knowledge, reducing cognitive dissonance. But in the process of fitting in new information, it can get twisted. Filling in what a face looks like under a mask, for example, is the brain twisting information to fit it in with what it already knows. This phenomenon happens all the time and is the science behind confirmation bias.

Human brains are extremely susceptible to confirmation bias, even going so far as to discard or ignore information that contradicts our beliefs (The science of stereotyping, 2022). The Smithsonian has a super cool interactive article about the science of bias if you are interested in learning more!

All of this to be said, our brains are amazing things, but they are not perfect. It is important to know that sometimes they take the easy path, twisting information to fit what we already know, from what someone looks like under a mask, to knowing a face-shaped rock is not a person.

 

References

Zhou, L.-F., & Meng, M. (2020). Do you see the “face”? Individual differences in face pareidolia. Journal of Pacific Rim Psychology, 14, e2. https://doi.org/10.1017/prp.2019.27

Kato, M., & Mugitani, R. (2015). Pareidolia in infants. PLOS ONE, 10(2), e0118539. https://doi.org/10.1371/journal.pone.0118539 

Kobayashi, M. et al. (2012). Do infants recognize the Arcimboldo images as faces? Behavioral and near-infrared spectroscopic study. Journal of Experimental Child Psychology, 111(1), 22-36. https://doi.org/10.1016/j.jecp.2011.07.008. 

Zhang, Q. et al. (2024). Understanding of facial features in face perception: insights from deep convolutional neural networks. Frontiers in Computational Neuroscienc, 18 https://doi.org/10.3389/fncom.2024.1209082 

University of Wisconsin–Madison Department of Psychology. (2022). The science of stereotyping. https://psych.wisc.edu/news/the-science-of-stereotyping/

Smithsonian Institution. (2021). The science of bias. https://biasinsideus.si.edu/online-exhibition/the-science-of-bias

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I am a biochemistry major at Georgia Tech and love nerding out about science! My favorite thing is when I can apply what I've learned in class to other topics. Right now, I've been loving using my organic chemistry knowledge to understand enzyme reactions and I can't wait to share that with you all!

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.