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Why do we forget our dreams?

April 19, 2018

dreams

You are halfway through saving a doomsday world from extraterrestrials or spending a night with a lost lover, when suddenly the sound of your alarm enters these storylines and comes to spoil the party. We’ve all been there, the feeling of waking up from a vivid dream that had us thinking we were among the likes of Quentin Tarantino or Christopher Nolan, but why then almost uncontrollably do we seem to forget these dreams as the day goes by. While scientific knowledge of dreams is still very undeveloped, there are two interesting evolutionary theories for why this happens.

Both theories stem from the fact that remembering these dreams, regardless of how cool they may be, are nonessential and sometimes even harmful to humans.

The first theory explains that our forgetfulness occurs as a natural response to continue learning and survival: for instance, in early cavemen, dreams of escaping lions by leaping off a cliff would not bode well when chased by a real lion.

The second evolutionary theory for dream forgetfulness was developed by Francis Crick, the co-discoverer of DNA. Crick believed that the function of dreams is to weed out unneeded thoughts and memories that accumulate over time in the brain, and dream recall defeats this primary evolutionary goal of dreaming. Our forgetfulness is generally attributed to neurochemical conditions in the brain that occur during REM sleep, a phase of sleep characterized by rapid eye movements and dreaming (1). It is interesting to note that after five minutes of a dream ending, we forget 50 percent of its content, and 90 percent of our dream’s detail is lost only 10 minutes later. Since most people wake up and immediately start thinking about how to start their day or other significant thoughts, these end up being the ones that get remembered. According to Crick, remembering dreams can leave the brain cluttered with useless information.

But what is it about dreams that make them so easy to forget, even when they can be so fascinating and graphic? It turns out it has to do with the nature of dreams, compared to reality. We are accustomed to remembering the past chronologically, linearly, and in terms of cause and effect. Dreams, however, are not always neatly arranged in time and effect — they meander and drift through different memory and emotional connections (2). Also, since dreams occur in deep sleep when a person is at rest, moving too much upon waking up can disrupt the memory of the dream much quicker.

After reading this, it may seem like grasping on to those vivid details of your precious dreams are not possible. While this is partially true, there are clearly methods to help with dream recall if one really cares to do so. Having to face and realize the construct of dreams (nonlinear, non sequential, etc), thinking about the dreams and only the dreams upon waking up, and limiting movement upon waking up can help someone remember more and more of those meaningful details of a lifelike dream. Also, writing down one’s memories of a dream upon waking up helps to recall more of the specific details. Using these methods can help to find those dreams our subconscious slept on.

 

References:

Hartmann, E. (2011, May 01). Why Do Memories of Vivid Dreams Disappear Soon After              Waking Up? Scientific American. Retrieved February 20, 2018, from                                    https://www.scientificamerican.com/article/why-do-memories-of-vivid-dreams/

Oldis, D. (2015, August 27). Why Do We Have Trouble Remembering Our Dreams?               Retrieved February 20, 2018, from                                                                                     https://www.huffingtonpost.com/dreamscloud/remembering-                                           dreams_b_8009552.html

 

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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.