by Brooke Napier
A wrinkle in your finger
It never really made sense to me that you would get wrinkled fingers from being in water, even when people would say that it was just your skin taking up water from the environment and swelling… Which is why it was particularly interesting to find out that the wrinkles in our fingers come directly from an involuntary nerve response. Specifically a reaction by the body’s autonomic nervous system, the system that also takes care of heart rate, digestion, respiratory rate, salivation, perspiration, papillary dilation, urination, and sexual arousal (I’m sure there are other functions too).
Well, turns out we’ve known that information for over 80 years, apparently we knew all along that if the nerve to the finger has been cut wrinkles cannot occur. Mark Changizi and colleagues thought perhaps this was an evolutionary mechanism, which allows your figures to morph into water drainage systems. While the water drains out of the fingers, it allows grip of surfaces and objects more efficiently in wet situations (like a tire!).
In fact, this past week an article published by Kareklas, et al. expanded on this evolutionary mechanism. They found that submerged objects are handled more quickly with wrinkled fingers than with unwrinkled fingers… supporting the idea that water-induced wrinkling of fingers and toes may be an adaptation for handling objects in wet conditions.
For more information on this topic read:
…and the primary articles:
Changizi, M., Weber, R., Kotecha, R., & Palazzo, J. (2011). Are Wet-Induced Wrinkled Fingers Primate Rain Treads? Brain, Behavior and Evolution, 77 (4), 286-290 DOI: 10.1159/000328223 Kareklas, K., Nettle, D., & Smulders, T. (2013). Water-induced finger wrinkles improve handling of wet objects Biology Letters, 9 (2), 20120999-20120999 DOI: 10.1098/rsbl.2012.0999
Trust in age
While perusing through the new weekly additions of journal articles I found a very interesting title, “Neural and behavioral bases of age differences in perceptions of trust”.
This paper, written by Elizabeth Castle and friends, shows that older adults, who are notably vulnerable to fraud, have a diminished “gut” response to cues of untrustworthiness. They showed older and younger adults faces and asked them to rate them on a scale of “untrustworthiness”. What they found was that older adults significantly found more trustworthy and approachable faces, and these data mimicked in neural activation.
The area of the brain devoted to the sense of “trustworthiness” is the anterior insula, which is more active while judging “untrustworthiness”, and is said to be the area of the brain devoted to “gut feelings”, which represent expected risk and predict risk-avoidant behavior. Essentially, the younger adults showed more neural activation in the anterior insula more frequently than the older adults.
TL;DR – there is science behind your Grandfather believing everything he hears on Fox News.
Primary literature found here:
Castle E, Eisenberger NI, Seeman TE, Moons WG, Boggero IA, Grinblatt MS, & Taylor SE (2012). Neural and behavioral bases of age differences in perceptions of trust. Proceedings of the National Academy of Sciences of the United States of America, 109 (51), 20848-52 PMID: 23213232