Love and the immune system

Valentine’s day is a day when we celebrate romantic love (well, some of us tend to) long before the famous greeting card company Hallmark was established. Fittingly, I found the perfect paper to cover for this occasion.

In the past couple of decades it became clear to scientists that there is no such thing as a mental experience that doesn’t have corresponding physical changes. Why should falling in love be any different? Several groups have already found that levels of some chemicals (oxytocin, cortisol, testosterone, nerve growth factor, etc.) change when we fall in love. There might be other changes as well. So Murray et al. (2019) decided to dive right into it and check how the immune system responds to love, if at all.

For two years, the researchers looked at certain markers in the immune system of 47 women aged 20 or so. They drew blood when the women reported to be “not in love (but in a new romantic relationship), newly in love, and out-of-love” (p. 6). Then they sent their samples to their university’s Core to toil over microarrays. Microarray techniques can be quickly summarized thusly: get a bunch of molecules of interest, in this case bits of single-stranded DNA, and stick them on a silicon plate or a glass slide in a specific order. Then you run your sample over it and what sticks, sticks, what not, not. Remember that DNA loves to be double stranded, so any single strand will stick to their counterpart, called complementary DNA. You put some fluorescent dye on your genes of interest and voilà, here you have an array of genes expressed in a certain type of tissue in a certain condition.

Talking about microarrays got me a bit on memory lane. When fMRI started to be a “must” in neuroscience, there followed a period when the science “market” was flooded by “salad” papers. We called them that because there were so many parts of the brain reported as “lit up” in a certain task that it made a veritable “salad of brain parts” out of which it was very difficult to figure out what’s going on. I swear that now that the fMRI field matured a bit and learned how to correct for multiple comparisons as well as to use some other fancy stats, the place of honor in the vegetable mix analogy has been relinquished to the ‘-omics’ studies. In other words, a big portion of the whole-genome or transcriptome studies became “salad” studies: too many things show up as statistically significant to make head or tail of it.

However, Murray et al. (2019) made a valiant – and successful – effort to figure out what those up- or down- regulated 61 gene transcripts in the immune system cells of 17 women falling in love actually mean. There’s quite a bit I am leaving out but, in a nutshell, love upregulated (that is “increased”) the expressions of genes involved in the innate immunity to viruses, presumably to facilitate sexual reproduction, the authors say.

The paper is well written and the authors graciously remind us that there are some limitations to the study. Nevertheless, this is another fine addition to the unbelievably fast growing body of knowledge regarding human body and behavior.

Shame that this research was done only with women. I would have loved to see how men’s immune systems respond to falling in love.

149-love antiviral - Copy.jpg

REFERENCE: Murray DR, Haselton MG, Fales M, & Cole SW. (Feb 2019, Epub 2 Oct 2018). Falling in love is associated with immune system gene regulation. Psychoneuroendocrinology, Vol. 100, Pg. 120-126. doi: 10.1016/j.psyneuen.2018.09.043. PMID: 30299259, PMCID: PMC6333523 [Available on 2020-02-01], DOI: 10.1016/j.psyneuen.2018.09.043 ARTICLE

FYI: PMC6333523 [Available on 2020-02-01] means that the fulltext will be available for free to the public one year after the publication on the US governmental website PubMed (https://www.ncbi.nlm.nih.gov/pubmed/), no matter how much Elsevier will charge for it. Always, always, check the PMC library (https://www.ncbi.nlm.nih.gov/pmc/) on PubMed to see if a paper you saw in Nature or Elsevier is for free there because more often than you’d think it is.

PubMed = the U.S. National Institutes of Health’s National Library of Medicine (NIH/NLM), comprising of “more than 29 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full-text content from PubMed Central and publisher web sites” .

PMC = “PubMed Central® (PMC) is a free fulltext archive of biomedical and life sciences journal literature at the U.S. National Institutes of Health’s National Library of Medicine (NIH/NLM)” with a whooping fulltext library of over 5 million papers and growing rapidly. Love PubMed!

By Neuronicus, 14 February 2019

Are you in love with an animal?

Sugar Candy Hearts by Petr Kratochvil. License: PD
Sugar Candy Hearts by Petr Kratochvil taken from publicdomainpictures. License: PD

Ren et al. (2015) gave sweet drink (Fanta), sweet food (Oreos), salty–vinegar food (Lays chips) or water to 422 people and then asked them about their romantic relationship; or, if they didn’t have one, about a hypothetical relationship. For hitched people, the foods or drinks had no effect on the evaluation of their relationship. In contrast, the singles who received sweets were more eager to initiate a relationship with a potential partner and evaluated more favorably a hypothetical relationship (how do you do that? I mean, if it’s hypothetical… why wouldn’t you evaluate it favorably from your singleton perspective?) Anyway, the singles who got sweets tend see things a little more on the rosy side, as opposed to the taken ones.

The rationale for doing this experiment is that metaphors alter our perceptions (fair enough). Given that many terms of endearment include reference to the taste of sweet, like “Honey”, “Sugar” or “Sweetie”, maybe this is not accidental or just a metaphor and, if we manipulate the taste, we manipulate the perception. Wait, what? Now re-read the finding above.

The authors take their results as supporting the view that “metaphorical thinking is one fundamental way of perceiving the world; metaphors facilitate social cognition by applying concrete concepts (e.g., sweet taste) to understand abstract concepts (e.g., love)” (p. 916).

So… I am left with many questions, the first being: if the sweet appelatives in a romantic relationship stem from an extrapolation of the concrete taste of sweet to an abstract concept like love, then, I wonder, what kind of concrete concept is being underlined in the prevalence of “baby” as a term of endearment? Do I dare speculate what the metaphor stands for? Should people who are referred to as “baby” by their partners alert the authorities for a possible pedophile ideation? And what do we do about the non-English cultures (apparently non-Germanic or non-Mandarin too) in which the lovey-dovey terms tend to cluster around various small objects (e.g. tassels), vegetables (e.g. pumpkin), cute onomatopoeics (I am at a loss for transcription here), or baby animals (e.g. chick, kitten, puppy). Believe me, such cultures do exist and are numerous. “Excuse me, officer, I suspect my partner is in love with an animal. Oh, wait, that didn’t come out right…”

Ok, maybe I missed something with this paper, as half-way through I failed to maintain proper focus due to an intruding – and disturbing! – image of a man, a chicken, and a tassel. So take the authors’ words when they say that their study “not only contributes to the literature on metaphorical thinking but also sheds light on an understudied factor that influences relationship initiation, that of taste” (p. 918). Oh, metaphors, how sweetly misleading you are…

Please use the “Comments” section below to share the strangest metaphor used as term of endearment you have ever heard in a romantic relationship.

Reference: Ren D, Tan K, Arriaga XB, & Chan KQ (Nov 2015). Sweet love: The effects of sweet taste experience on romantic perceptions. Journal of Social and Personal Relationships, 32(7): 905 – 921. DOI: 10.1177/0265407514554512. Article | FREE FULLTEXT PDF

By Neuronicus, 21 October 2015