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Exploring the Scientific Credibility of Personality Tests and Astrology

December 6, 2023

What Harry Potter house are you? What’s your mbti? What’s your zodiac? What kind of fruit are you? What are your big three? 

I’ve asked and been asked these questions time and time again. I’ve always enjoyed categorizing myself and compartmentalizing aspects of my personality to fit into aesthetic groups. I’m personally a Hufflepuff, an INFP, and a Taurus. I’ve never thought about whether or not there was any real science behind these types of classifications. Is there any scientific or data-driven backing for these? Why do we spend so much time thinking about what our MBTI is or what kind of personality type we have? 

Let’s first dive into the history and of some of these. 

History of MBTI or Myers-Briggs Type Indicator

Briggs and Myers, a mother-daughter team, aspired to delve into the intricacies of diverse personality types by integrating Carl Jung’s concepts into their own framework. Myers held the conviction that through their assessment, individuals could enhance their comprehension of one another’s personalities, fostering improved collaboration and minimizing conflicts.

What stands out prominently is that neither Briggs nor Myers possessed formal training in psychology. Briggs, with a keen interest in children’s psychology, aimed to develop a tool for early childhood education and specialization. Her daughter, Myers, adopted this perspective and envisioned using the indicator as a means to assist individuals in finding happiness.

History of Astrology

Prior to astrology, divination held sway, involving the interpretation of the influence exerted by stars and planets on earthly matters and human destinies. The roots of astrology can be traced back to Mesopotamia, traversing through India, Greece, China, Islamic culture, and Arabic learning.

According to Greek tradition, the heavens are delineated by the 12 constellations of the zodiac, each believed to possess a spiritual influence on human affairs. Astrology has permeated various cultures, and many contemporary individuals adhere to the notion that horoscopes wield control or significant influence over our lives.

Now, we confront a pivotal question: is there any scientific substantiation for these beliefs? Can they be deemed reliable in any capacity?

Fact or Fiction: MBTI

As previously noted, the foundation of MBTI is rooted in Carl Jung’s theoretical exploration of psychological types, focusing on different states of consciousness rather than distinctly defined personality types. 

For a personality assessment to be considered a meaningful measurement tool, it must exhibit both reliability and validity—qualities notably absent in MBTI. Many individuals experience inconsistent outcomes when taking the test multiple times, raising questions about the assessment’s significance. Clearly, the answer is in the negative.

Despite its lack of credibility, MBTI remains widely embraced, primarily due to the Barnum or Forer effect. This phenomenon reflects people’s tendency to readily accept vague and generic personality descriptions as personally insightful. While the scientific evidence supporting this personality test is limited, it may still be enjoyed for amusement purposes.

Fact or Fiction: Astrology

Starting with the foundation, astrology relies on celestial bodies such as the sun, moon, planets, and constellations. It utilizes the positions and movements of these heavenly bodies to formulate predictions and explanations for various aspects of human life, events, and personality traits.

Similar to the MBTI, astrology encounters comparable challenges, notably in the tendency to generate overly broad expectations, allowing interpretations that can apply to almost any outcome. Consequently, astrology lacks testability, and the available evidence fails to substantiate the validity of its concepts. In the scientific realm, ideas undergo modification based on compelling evidence, a principle not embraced by astrology, which remains unchanged despite contradictory evidence.

Furthermore, astrology faces criticism within the scientific community regarding the dissemination of research. Typically, published astrological articles lack the scrutiny of peer review, a fundamental practice in scientific inquiry. Additionally, there is an absence of documented instances where astrology has contributed to significant scientific discoveries.

Final Thoughts

In conclusion, while personality frameworks like MBTI and astrological concepts such as horoscopes and zodiacs have garnered widespread popularity and cultural significance, their scientific foundations remain highly debated and often contested. The lack of empirical evidence, inconsistent test-retest reliability, and the tendency for generalized statements to resonate with a broad audience raise skepticism about the validity of these systems from a scientific standpoint. While these frameworks may provide personal insights or entertainment for some, it’s essential to approach them with a critical mindset and acknowledge their limitations in terms of scientific rigor and empirical support. As our understanding of psychology and the universe continues to evolve, a cautious and discerning approach is advisable when considering the scientific legitimacy of such personality assessments and astrological beliefs.

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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.