Most people who grow up in industrialized environments will be at least a little bit tricked by this optical illusion, called the Müller-Lyer illusion. At first look, it may seem as if the line on the left is shorter than the line on the right. In fact, if you look closely and carefully, you can probably see that both lines are the same length.
Some psychologists theorize that susceptibility to this illusion is due to a strongly “carpentered” environment, one built by humans with the help of machines. Such environments are made mostly of straight lines and right angles. If this geometry is all around us all the time, our brains get very good at interpreting these environments.
That advantage, though, is a disadvantage when looking at the Müller-Lyer lines because our brain learns to associate angles like the one on the right with distance and ones like the one on the left with closeness. Then, it alters our perception of their height to adjust for perceived space.
Bear with me.
Consider my drawing of a room and hallway below. You can see that the corner closest to us (A) has lines like the point of an arrow on both ends (like the line on the left above), while the one further away (B) has lines like the rear of an arrow on both sides (like the line on the right). Our brain gets so used to inferring distance when it sees these angles, it assumes that any line with angles like B appears inaccurately short because it’s far away. That’s how the illusion tricks our brain.
People who don’t grow up in a carpentered environments, though—hunter gatherers and other groups who spend most of their time in nature and other uncarpentered environments—don’t have brains adjusted to understanding straight lines and angles, so the illusion doesn’t work on them.
The Müller-Lyer illusion, then, is a great example of how our brains get acculturated in ways that shape even simple and straightforward perception tasks.
I heard stories this week about dung beetles and cuttlefish. Both made me think about the typical stories we hear in the media about evolved human mating strategies. First, the stories:
Story #1 :The Dung Beetle
A story on Quirks and Quarks discussed the mating strategies of the dung beetle. The picture above is of a male beetle; only the males have those giant horns. He uses it to defend the entrance to a tiny burrow in which he keeps a female. He’ll violently fight off other dung beetles who try to get access to the burrow.
So far this sounds like the typical story of competitive mating that we hear all the time about all kinds of animals, right?
There’s a twist: while only male dung beetles have horns, not all males have horns. Some are completely hornless. But if horns help you win the fight, how is hornlessness being passed down genetically?
Well, it turns out that when a big ol’ horned male is fighting with some other big ol’ horned male, little hornless males sneak into burrows and mate with the females. They get discovered and booted out, of course, and the horned male will re-mate with the female with the hopes of displacing his sperm.
Those little hornless males have giant testicles, way gianter than the horned males. While the horned males are putting all of their energy into growing horns, the hornless males are making sperm. So, even though they have limited access to females, they get as much mileage out of their access as they can.
The result: two distinct types of male dung beetles with two distinct mating strategies.
Story #2: The Giant Australian Cuttlefish
The Naked Scientists podcast featured a story about Giant Australian Cuttlefish. During mating season the male cuttlefish, much larger than the females, collect “harems” and spend their time mating and defending access. Other males try to “muscle in,” but the bigger cuttlefish “throws his weight around” to scare him off. The biggest cuttlefish wins.
So far this sounds like the typical story of competitive mating that we hear all the time about all kinds of animals, right?
Well, according The Naked Scientists story, researchers have discovered an alternative mating strategy. Small males, who are far too small to compete with large males, will pretend to be female, sneak into the defended territory, mate, and leave.
How do they do this? They change their color pattern and rearrange their tentacles in a more typical female arrangement (they didn’t specify what this was) and, well, pass. The large male thinks he’s another female. In the video below, the cuttlefish uses his ability to change the pattern on his body. He simultaneously displays a male pattern to the female and a female pattern to the large male on the other side.
So, can the crossdressing cuttlefish and dodge-y dung beetle tell us anything about evolved human mating strategies?
But I do think it tells us something about how we should think about evolution and the reproduction of genes. If you listen to the media cover evolutionary psychological explanations of human mating, you only hear one story about the strategies that males use to try to get sex. That story sounds a lot like the one told about the horned beetle and the large male cuttlefish.
But these species have demonstrated that there need not be only one mating strategy. In these cases, there are at least two. So, why in Darwin’s name would we assume that human beings, in all of their beautiful and incredible complexity, would only have one? Perhaps we see a diversity in types of human males (different body shapes and sizes, different intellectual gifts, etc) because there are many different ways to attract females. Maybe females see something valuable in many different kinds of males! Maybe not all females are the same!
Let’s set aside the stereotypes about men and women that media reporting on evolutionary psychology tends to reproduce and, instead, consider the possibility that human mating is at least as complex as that of dung beetles and cuttlefish.
Monday marked the 50th anniversary of the intervention of the birth control pill. There is no doubt that the pill has had a huge influence on sexual attitudes, sexual activity, and how much control women had over their own fertility. The pill, although it may not be the right choice for everyone, should be celebrated for these reasons. But there is something else to consider here: how did the invention of the pill shape the way that women (and the medical community for that matter) view periods?
When you think of the pill, the first image that comes to mind is that iconic little container of pink and white pills that represents one menstrual “cycle.”
In Malcolm Gladwell’s fantastic article, John Rock’s Error, Gladwell explains how the invention of the pill was heavily influenced by the Catholic Church. One of the creators of the pill, a devout Catholic, wanted it to be viewed as “natural” since it used chemicals that naturally occur in the body to prevent pregnancy. It was necessary, then, for women to continue to have their period regularly to show that the pill did not interfere with a woman’s menstrual rhythm.
But, speaking from an evolutionary standpoint, there is nothing natural about having a menstrual period every month because it is not natural to limit fertility. Our female ancestors spent a good portion of their reproductive years pregnant and not having a period. And, in fact, having a period every month can be dangerous. Every time a woman has a period, tissue lining sheds and new cells must grow to replace it. And every time there is cell regrowth there is a new chance for mutations to occur. This leads to an increased risk of cancer and cysts.
It may be healthier (and more natural), then, for women to suppress menstruation (the way pregnancy used to). But because the idea of a natural rhythm is now synonymous with monthly periods, introducing pills with alternative cycles has proven difficult. Pills that allow for four periods a year (like Seasonale, Seasonique, and Yaz) have come on the market. But instead of discussing the medical benefits of fewer periods, they are marketed in a woman-on-the-go sort of way, as a way for women to “take back” their lives by avoiding an inconvenience.
Marketing the pill in this fashion has created push back by women who think this method this pill is all about suppressing “natural” womanhood, but it is a falsely constructed version of womanhood to begin with.
A study published in 2001, to which I was alerted by Family Inequality, asked undergraduate college students their favorite color and presented the results by sex. Men’s favorites are on the left, women’s on the right:
The article is a great example of the difference between research findings and the interpretation of those findings. For example, this is how I would interpret it:
Today in the US, but not elsewhere and not always, blue is gendered male and pink gendered female. We might expect, then, that men would internalize a preference for blue and women a preference for pink. We live, however, in an androcentric society that values masculinity over femininity. This rewards the embracing of masculinity by both men and women (making it essentially compulsory for men) and stigmatizes the embracing of femininity (especially for men).
We might expect, then, that men would comfortably embrace a love of blue (blue = masculinity = good), while many women will have a troubled relationship to pink (pink = femininity = devalued, but encouraged for women) and gravitate to blue and all of the good, masculine meaning it offers.
That’s how I’d interpret it.
Here’s how the authors of the study interpreted it:
…we are inclined to suspect the involvement of neurohormonal factors. Studies of rats have found average sex differences in the number of neurons comprising various parts of the visual cortex. Also, gender differences have been found in rat preferences for the amount of sweetness in drinking water. One experiment demonstrated that the sex differences in rat preferences for sweetness was eliminated by depriving males of male-typical testosterone levels in utero. Perhaps, prenatal exposure to testosterone and other sex hormones operates in a similar way to “bias” preferences for certain colors in humans.
Important lesson here: data never stands alone. It must always be interpreted.
“Future research is needed to identify the process,” write the authors, but it appears that pregnant women have some control over when they give birth. A study of birth incidence on Halloween and Valentine’s Day, by public health scholar Becca Levy and colleagues, showed that spontaneous births dipped on the former and rose on the latter.
The authors suggest that this contributes to growing evidence that culture influences birth timing. Women’s bodies resist giving birth on a day associated with fright and death, but give into birth on a day associated with love. The authors recommend extra staffing on obstetric wards on Valentine’s Day and sending a few more doctors and nurses into the streets on Halloween.
Back when I was in high school and college, I learned that one of the major things that separated humans from other species was culture. The ability to develop distinct ways of living that include an understanding of symbols, language, and customs unique to the group was a specifically human trait.
And, ok, so it turned out that other species had more complex communication systems than we thought they did, but still, other animals were assumed to behave according to instinct, not community-specific cultures.
But as with so many things humans have been convinced we alone possess, it’s turning out that other species have cultures, too. One of the clearest examples is the division of orcas into two groups with distinct customs and eating habits; one eats mammals while the other is pescetarian, eating only fish. Though the two groups regularly come in contact with each other in the wild, they do not choose to intermingle or mate with one another. Here’s a video:
Aside from the obvious implications for our understanding of culture, this brings up an issue in terms of conservation. Take the case of orcas. Some are suggesting that they should be on the endangered species list because the population has declined. What do we do if it turns out at some point that, while the overall orca population is not fully endangered, one of the distinct orca cultural groups is? Is it enough that killer whales still exist, or do we need to think of the cultures separately and try to preserve sufficient numbers of each? In addition to being culturally different, they are functionally non-interchangeable: each group has a different effect on food chains and ecosystems.
Should conservation efforts address not just keeping the overall population alive and functioning, but ensure that the range of cultural diversity within a species is protected? If this situation occurred, should we declare one orca culture as endangered but not the other? Are both ecological niches important?
I love these questions. If we recognize that creatures can have cultures, it challenges our sense of self, but also brings significantly more complexity to the idea of wildlife preservation.
Originally posted in 2010.
Gwen Sharp is an associate professor of sociology at Nevada State College. You can follow her on Twitter at @gwensharpnv.
A new study finds that people with high “justice sensitivity” are using logic, not emotions. Subjects were put in a fMRI machine, one that measures ongoing brain activity and shown videos of people acting kindly or cruelly toward a homeless person.
Some respondents reacted more strongly than others — hence the high versus low justice sensitivity — and an analysis of the high sensitivity individuals’ brain activity showed that they were processing the images in the parts of the brain where logic and rationality live. “Individuals who are sensitive to justice and fairness do not seem to be emotionally driven,” explained one of the scientists, “Rather, they are cognitively driven.”
Activists aren’t angry, they reasonably object to unjust circumstances that they understand all too well.
Image borrowed from Jamie Keiles at Teenagerie, who is a high sensitivity individual.
Forgive me, because this is probably better left to Cyborgology, but something amazing is happening here. In the video below, nesting swallows become trapped in a building when they add doors. The birds soon learn, though, that they can get the doors to automatically open by triggering the motion sensors. This is a story, obviously, of how smart birds are, but here’s what struck me: we often think about human technology as for humans. In this case, however, birds adapted the technology for their own very similar needs (to get in and out).
If the workers had installed an older human technology — plain old doors — the birds would have been out of luck because they don’t have thumbs and the strength to manipulate an environment built for humans. But motion activated doors make both thumbs and strength irrelevant, so now birds are our functional equals.
This is fascinating, yeah? Our technology has advanced to the point where we’re potentially undermining our own evolutionary advantages. I’m not putting a moral judgment on it. I think morality is firmly on the side of non-fitness based decisions (eh em, social Darwinism). If one wants to theorize the relationship between animals, technology, and what it means to be human, however, this looks like gold to me.