All Work and No Play

The cover image was sourced from https://doi.org/10.1016/j.cub.2014.09.020.

If you’ve ever fallen down the easily addictive, low-stress rabbit hole that is the world of wonderfully awesome animal videos, you might have come across this video of a crow in Russia, sliding down a snow-covered roof while perching on a jar lid.

While it’s easy to think that this crow went sledding purely for their own enjoyment, scientists aren’t content with that conclusion – thinking in such an anthropomorphic way projects our own human thoughts and feelings onto animals who, while exhibiting familiar behaviors, may not be doing it for the same reasons we do (Emery & Clayton, 2015).

But, regardless of what we may think, birds do play! What does that look like? Well, most forms of play are divided into one of several categories: the first broad category being locomotor play, which includes all kinds of flight-related play – hanging from surfaces, flying upside down (Emery & Clayton, 2015), and even sledding down a snowy roof in Russia!

Social play involves interactions between birds – there’s play chasing, where one bird follows another, whether on the ground or through the air. We also have play fighting, where two birds engage in actions adopted from antagonistic behaviors. There’s also play invitation, where two birds engage in actions that occur primarily before play. Finally, we have social object play, where two birds engage with one or more objects in their environment (Bond & Diamond, 2003).

While we briefly touched on it, object play itself can be considered another major category of play – involving exploration, curiosity, object manipulation, where birds learn about the structure of objects, if they’re edible or not, and how they might work (Emery & Clayton, 2015).

Figure 2 Source: https://corvidresearch.blog/wp-content/uploads/2015/03/northwestern-crow-youngsters-playing-tug-of-war_595.jpg

The problem with researching play is that birds don’t necessarily need a reason to play – even when considering the anthropomorphic projection we cast onto them from our human perspectives, it can be as simple as having fun!

“Fun”, at least, in the context of the brain, involves taking part in something rewarding that provides a sense of pleasure. You may have heard of the neurotransmitter dopamine… it plays an important role in the reward-seeking system, controlling the search for reward-inducing stimuli for almost all creatures (Emery & Clayton, 2015).

When people come across phenomena like this in the wild, the answer that tends to come to mind often lies on the justifying end of the spectrum; in our attempt to be objective, we may implicitly assign a “value” to that act of play. Perhaps birds play fight to practice hunting, perhaps birds engage in social play to form strong, interconnected networks, and perhaps that crow slid down that roof to learn how to use that lid!

Studies done on the potential concrete benefits of play – such as relative brain size, for instance – ultimately find that there is little to no predictive value between the complexity of play with those benefits. As such, it is hard to say whether or not the act of play is utilitarian in nature (Bond & Diamond, 2003).

Does that mean that play is inherently fun? Once again, it’s hard to say! Humans, after all, may be the only species that have the luxury of leisure time. The time we spend solely pursuing pleasure: games, hobbies, activities we may find fun, are all a product of modern developments. We no longer have to hunt or grow our own food, we no longer have to worry about predators, we no longer have to worry about forming civilized societies – but birds, and by extension, all other animals, do (Emery & Clayton, 2015)!

Perhaps that is the underlying reason why we believe play has to have a purpose. Wild animals have a limited time to find food, find water, avoid predators, find a mate, raise offspring, all in the name of the cycle of life. Why, then, would a bird waste its time playing for the sake of playing? Why, then, do we have examples of crows sledding through the snow?

All of these questions are interesting to ponder, and I personally don’t have all the answers. The realm of neuroscience is far out of my understanding, but I hope I’ve done a good job setting the stage for this interesting question.

I’ll leave things here with a plan of action to you, the reader – whenever you see a cute animal video in the future, think to yourself: why could this be happening? Is it play, or is it intentional? Most importantly, though… why is it so gosh darn adorable?!

Reference List

Bond, A., & Diamond, J. (2003). A Comparative Analysis of Social Play in Birds. Behaviour, 140(8-9), 1091–1115. https://doi.org/10.1163/156853903322589650

Emery, N., & Clayton, N. (2015). Do birds have the capacity for fun? Current Biology, 25(1), R16–R20. https://doi.org/10.1016/j.cub.2014.09.020

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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.