Losing our minds in middle age

When negative stress affects our well-being, we sometimes feel like we are losing our minds...

But when in the lifespan does this really happen? When do we lose our brains?

Until age two we experience rapid growth of brain cells, or neurons. Around that age, rarely used neurons and unneeded connections between neurons (synapses) are reduced. Past research by Hedman, van Haren, Schnack, Kahn, and Hulshoff (2012) suggests that childhood is a time of brain growth, with more neurons being produced. Starting around age thirteen and continuing through adolescence we see brain volume loss as pruning reoccurs so that our brains can be more efficient. Most of young adulthood sees little change in brain volume, but starting at age 35, MRI scans demonstrate a yearly loss of about 0.2% of brain volume. This loss accelerates in older age: in our sixties this increases to a loss of about 0.5% of brain volume every year; this acceleration is often given as one of many explanations for other normal declines associated with aging.

To examine in detail the brain volume loss during the transition to midlife, Guo, Isohanni, Miettunen, Jääskeläinen, Kiviniemi, Nikklinen, Remes, Huhtaniska, Veijola, Jones, and Murray (2016) examined MRI scans of 43 men and 23 women as they aged from their 30s (33-35 years) to their 40s (42-44 years). The participants in this longitudinal study were part of the Northern Finland 1966 Birth Cohort so they should have had similar experiences in their lives as they grew up at the same time. The researchers' goals were to measure overall brain volume at both ages, to identify the locations of any loss as observed in the second MRI performed when the participants were in their 40s, and to clarify any sex differences that emerged.

Total brain volume decline was higher than predicted by past research: on average men lost 3.21% and women lost 4.03%. This sex difference was very small but it reached statistical significance, meaning that the difference was unlikely to be due to chance.

The location of loss also showed a sex difference. After taking into account percentage of total brain loss, Guo et al. found that men lost most of their neurons in the midline areas (specifically: bilateral precentral gyri; bilateral paracingulate gyri; and bilateral supplementary motor cortices). Most of these areas relate to motor skills and one may be involved in decoding certain emotions.

Women's loss was more spread out with most of it occurring in the outer brain (specifically: bilateral frontal parietal; temporal lobe; occipital cortex; cerebellum). These areas relate to language, motor skills, sensory interpretation, vision and visual memories, and emotion association.

Guo et al. did not make guesses beyond a quick mention of hormones as to what caused the sex differences in overall brain loss or the sex differences in loss locations. They also speculated that these differences may translate into differences in midlife men's and women's health or behavior, yet they did not offer any examples.

That leaves us all free to speculate. One bit of demographic information that caught my eye was that the researchers coded participants on "parental leave" as working full-time, because it meant that the participants usually worked full-time but were absent from that work to take care of a newborn child. This made me think about other research related to brain volume and parenting. For example, when women are pregnant their brain volumes can shrink an average 4% and not return to normal volume until about six months after birth. First, that makes the 4.03% decline found in Guo et al.'s female participants sound less ominous: this sort of decline is a normal experience for many women in young adulthood. Second, although most Finnish women in the 1980s usually started having babies at age 29, is it possible that some of the 23 women in this study gave birth just before the second MRI scan? Or is the location of brain loss during pregnancy similar to the location of women's brain loss in the transition to middle age?

Starting in the 80s, Finland offered parental leave to fathers as well as mothers. So it is possible that some of the male participants may have also identified themselves as being on parental leave. However, we know that fathers and mothers often take on different roles in parenting. For example, women are more likely to report that they get up to feed or care for babies in the middle of the night; mothers report more sleep loss than fathers even as children grow older. Poor sleep is associated with brain volume loss in the frontal, temporal, and parietal lobes. Different parental roles and related sleep loss may contribute to women's additional 1% of brain loss; brain volume loss related to poor sleep and brain volume loss related to women's transition to midlife are located in similar areas.

In the end we do not know what is causing these declines or sex differences, and even if we did, at this point we cannot know if these are related to any changes in men's and women's behavior or health as they age. The one thing you can know for sure is that if you are middle aged, pregnant, a new mother, or are sleep-deprived, you ARE losing your mind.

FURTHER READING:

The Guo et al. (2016) article can be accessed online or through your local college library.

Loss of brain cells does not always relate to loss of cognitive functioning. Read an APA Monitor on Psychology article by Melissa Phillips on the strengths of the middle-aged mind.

Childhood trauma can also reduce brain volume. Read a report on trauma's effects on brain development from the Child Welfare Information Gateway (U.S. Dept. of Health and Human Services).

BONUS:

Watch a video from Brown University on Synaptic Pruning:

Puberty: Getting more than you hoped

When I was growing up, all the girls read Are you There God? It's Me Margaret., by Judy Blume. Its main character, Margaret, looks forward to developing breasts and getting her first menstrual period. When these finally occur she feels triumphant! More recently, Hello Flo advertisements also portray puberty as something that girls desire: they are upset if menstruation doesn't start quickly enough. Of course, fiction writing and advertisements may not reflect the full story of girls' puberty as witnessed by these memes:



Keenan, Culbert, Grimm, Hipwell, and Stepp (2014) investigated the relationship between African-American and European-American girls' pubertal timing (what age things happen), pubertal tempo (how much time passes between stages of puberty; how long puberty lasts), and depression symptoms. Their sample was part of the longitudinal Pittsburgh Girls Study, so it was large (more than 2,000 girls of diverse backgrounds), data were collected at age 10 and then each year for up to a decade, and the participants were more likely to come from low-income homes.

Each year the girls completed a depression inventory; their caregivers (mostly mothers) completed the same depression inventory about their daughters. From this Keenan et al. could learn how many depression symptoms were common at each age and see how they related to the other variables of ethnicity and puberty. Overall, depression symptoms were highest at age 10 and declined at various rates after that. Even so, across the decade the girls reported that only one or two symptoms on average. The authors maintained that even "minor depression" like this can put individuals at risk for other problems.

The girls provided data on pubertal timing and tempo by matching themselves to standard pictures that portrayed different stages of breast and pubic hair development, and by indicating if they had gotten their first period. One of these scales was also completed by the caregivers in reference to their daughters' development.

The results replicated past research in that the earliest maturing girls (early pubertal timing for breast and pubic hair development) reported more depression symptoms at age 10 than later maturing girls (late pubertal timing). A new finding was that girls who were late to develop breasts (late pubertal timing) and also had a slow pubertal tempo (change progressed slowly) also reported more depression symptoms. There was no effect on depression related to the development of pubic hair and pubertal tempo.

Similar to past research, African-American girls reported slightly higher depression symptoms. For example, at age 10 African-American girls reported one extra depression symptom compared to European-American girls. Likewise, African-American girls demonstrated earlier pubertal timing: pubic hair development occurred almost nine months earlier and breast development began about eleven months earlier than what was reported by European-American girls. Keenan et al. added to the literature by suggesting a trend: African-American girls demonstrated a little slower pubertal tempo, meaning that they took just ever so slightly longer to pass through the stages of puberty compared to the European-American girls. This trend requires further investigation in future research.

New and most importantly, the relationship between depression, ethnicity, and pubertal timing was significant. The ethnic difference in depression symptoms at age 10 (their peak) was reduced up to 32% when pubertal timing was factored in. Pubertal tempo did not have a similar effect. Thus, a considerable portion of the ethnic difference in depression can be explained by African-American girls' earlier entry into puberty compared to European-American girls.

In explaining their findings Keenan et al. suggested that sex hormones might be to blame for at least some of the low level depression seen in preteen girls. Girls with an earlier pubertal timing have higher levels of sex hormones like estrogen compared to girls who have not yet begun pubertal development. This biological argument would, at least in part, explain African-American girls' slightly higher rates of depression.



On the other hand, the authors predicted that a slow pubertal tempo would also predict higher levels of depression because it would mean exposure to high levels of hormones for an extended period of time. In this study, only for girls with later breast development (which implies lower hormone levels) did slow pubertal tempo predict slightly higher depression symptoms. As well, slow pubertal tempo did not explain any of the differences in depression between African- and European-American girls. So hormones cannot be the only explanation for girls' depression symptoms during puberty.

One possibility is that girls receive feedback based on their development that makes them self-conscious. Increases in estrogen cause weight gain so an early maturing girl may feel overweight compared to other girls. Breast development, a sign of puberty that is visible to others, may be desired to attract dating partners - so later maturing girls (especially those with a slow tempo) might be embarrassed by smaller breasts (but not care about lacking pubic hair, a trait that is not socially visible). Conversely, early breast development may bring with it unwanted sexual attention and comments that are uncomfortable for a young girl to navigate. It is also possible that early development of breasts and early menarche may lead parents to treat girls differently: for example, fathers may be less affectionate with their daughters once puberty begins. Parents, fearing sexual experimentation, sexually transmitted infections, teen pregnancy, or sexual assault may also impose new limits on what an early maturing girl can wear, where she can go, and whom she can be with. These sorts of social factors could also explain some of the low level depression seen in preteen girls.

FURTHER READING:

The Keenan et al. (2014) article is available online and through your local college library.

Parents are not the only ones who may regulate girls bodies once puberty begins. Read an article in The Atlantic magazine by Li Zhou: "The Sexism of School Dress Codes."

Starting at puberty, girls and women are twice as likely as boys and men to suffer from depression. This also means that depression symptoms might be missed in males because we are not expecting them to be depressed. Counselor and writer, Michael Gurian, explains some possible symptoms to look for in boys:

What we fear is a mirror

Along with trick-or-treating and attending parties, some people celebrate Halloween by paying to get scared: they walk through the spooky scenes of a haunted house while actors jump from the shadows, scream, and taunt them.

Why do we like to get a little scared? The James-Lange theory of emotion would suggest that we experience our bodies' fear response, racing hearts and sweaty palms, but then mislabel that arousal as "fun" or "excitement." As well, haunted houses keep us in the present moment so we cannot worry about anything else at the same time. People who were stressed before going into a haunted house often report the highest amount of relaxation from the experience.

But do we all get scared by the same things? Muroff, Spencer, Ross, Williams, Neighbors, and Jackson (2014) wondered if White and African American men and women have different ideas of what causes fear. They used a cognitive interview technique by asking a convenience sample of almost 200 participants (ages 18-85) a single question, "What makes and object or a situation fearful?" (p. 156).

From their answers the researchers distilled five categories of what makes something scary:

External Locus of Control: feeling out of control; not knowing what is about to happen.

Harm/Danger: risk that something would hurt or threaten your health/life.

Phobias: an irrational, intense fear of something that provokes immediate anxiety and/or panic.

Past Experience: having had or knowing about someone else's past experience with something that was fear-inducing.

Self-Perception: your belief that you will find something scary or not be able to handle something.

Muroff et al. then reexamined the participants' responses to see how often all of the participants and participants from specific groups included these categories in their original explanations about what makes things scary. From these qualitative data, they found that (p. 157):

*The most common category for all participants was External Locus of Control: it was mentioned in 35% of all explanations. This was followed by Harm/Danger (29%) and Phobias (18%).

*White women were 1.5 times more likely than African-American women to include External Locus of Control as part of their answers.

*External Locus of Control appeared most in the explanations given by White women and the least in explanations given by White men. 

*Older participants' responses were more likely to include External Locus of Control.

*White men were 3.5 times more likely than African-American men to include Past Experience in their responses.

*Men were more likely than women to include references of Self-Perception.

*Phobia was most common in the answers given by participants who had not completed high school.

This would suggest that these same individuals would react differently to various aspects of a haunted house. The majority, but especially White female and older participants, would be scared by unpredictable situations: dark passageways; rooms filled with disorienting lighting and mirrors; going around blind corners; not being able to find the way out of a room.

White male participants would be scared of things that remind them of bad situations that they, or people they know, have experienced. For example, an actor throwing a fake punch toward them, or a torture scene that includes an actor being kicked in the genitals or having a thumb hit by a hammer.

Males, in general, would also be afraid if they were led to believe that they could not handle a situation. This could be induced by playing recorded messages like, "You are helpless," "Others have come here but nobody leaves alive," or, "You can fight but you are too weak to escape," as they walk through the haunted house.

Finally, participants who had not completed high school might be particularly afraid if the horrific scenes included common phobia triggers. For example, spiders, needles, blood, tight spaces, or high heights.

Muroff et al. were not interested in how to build the scariest haunted house. Instead they were curious if people from different groups may have different interpretations of an assessment question that is commonly used to diagnosis phobias. Their results suggest that age, education level, sex, and race can influence how people conceptualize fear, and this may affect the accuracy of that phobia assessment.

The authors emphasized that the results likely reflect truly scary aspects of American culture. For example, women tend to have less financial power related to men; money allows you to better control your experiences. I would also add that women are more often cautioned to control their environments to prevent dangerous situations (e.g.; never walk alone; don't leave your drink unattended; walk with purpose and stay in well-lit areas). This may be particularly true for White women as the media more often portrays them as victims of violence - even though it is African American women who actually experience more violence. Perhaps this is why White women were more likely to endorse External Locus of Control as something that induces fear.

More clearly, Muroff et al. wrote, "Research on coping mechanisms for discriminated and stigmatized groups suggests that African American men and women may depend on various mechanisms for coping such as external locus of control and social learning" (p. 158). In this case external locus of control means that discrimination is explained as being random or a product of the situation, and thereby not caused by the person experiencing this unfair treatment. The authors explained that this beneficial coping mechanism would be less likely to be part of African Americans' explanations of fear.

Additionally they wrote, "Our findings also suggest that White respondents in this sample mention past experiences in their conceptualizations of fear more frequently than their African American counterparts. African Americans' experiences may be influenced more by unpredictable events including acts of racism and discrimination." Because of this, "African Americans may focus on the present and future in order to cope with adverse life experiences" (p. 158). When your past is full of fear it might not help you distinguish if a new situation is scary or not.

We can all exit a haunted house, but we can rarely step outside of our own experience of biological sex, race, and culture. The first step is to realize that we are all different: the same environment may be fun for some and scary for others.

Further Reading:

The Muroff et al. (2014) article can be accessed through your local college library.

Listen to National Public Radio's "Hidden Brain" podcast on the Science of Fear.

Read about Neuroscientist Dr. Lisa Feldman Barrett who creates a yearly haunted house in her basement based on the neuroscience of fear. The proceeds of the event are donated to charity.

BONUS:

Watch when talk show host Ellen Degeneris sends her executive producer and "Modern Family" star, Eric Stonestreet, through a haunted house. These men are both White: does their behavior match the results of Muroff et al.?

Andy Goes to a Haunted House with Eric Stonestreet, Part 2 | EllenTV.com

How to make an introvert smile

On social media I have seen a lot of posts about introverts and extraverts (or extroverts): things they want us to know; their everyday struggles; things we can do for them. These traits have been around for a long time and comprise one of the Big Five aspects of personality. In short, introverts get energized by alone time whereas extraverts are energized by time with others. This difference is demonstrated by our meme featuring Introvert Cat:

This meme implies that introverts would prefer to eat alone rather than go out to eat with people they like. It also implies that introverts enjoy solitude more than socializing. However, past research suggests that both introverts and extraverts get more enjoyment from socializing than they do from being alone. If everyone has more fun acting extraverted, why might Introvert Cat shy away from such an opportunity?

One suggestion is highlighted in research done by Zelenski, Whelan, Nealis, Besner, Santoro, and Wynn (2013). In a preliminary study they asked introverts and extraverts to imagine themselves in different scenarios: some scenarios would require them to act introverted whereas the other scenarios would require them to act extraverted. For each scenario 97 undergraduate participants, who had been classified as introverted or as extraverted, rated themselves on a list of positive and negative adjectives based on how they thought they would feel: this was a measure of their affective forecasting. The results demonstrated that when introverts imagined themselves acting extraverted, they were more likely than extraverts to predict negative emotions and feeling self-conscious, and less likely than extraverts to predict positive emotions and enjoyment. However, these results cannot tell us what either group's emotional experiences would be in a real-world situation that calls for them to act one way or the other.

To get closer to that answer, Zelenski et al. conducted four follow-up experiments from which the results were combined. Thus 495 undergraduate students, who had been classified as introverted or extraverted, were randomly assigned to act either introverted or extraverted while interacting with others in a laboratory setting. In each experiment the participants were given instructions on how they should act, then asked to imagine how they will feel once the interaction begins - again, they rated themselves on adjectives to measure their affective forecasting. Next, they interacted with others in one of four ways: taking part in a group discussion with other participants; being interviewed by a confederate; planning a day's activities or building with blocks while partnered with a confederate; putting together a timed puzzle with other participants. At the end of each experiment, the participants rated how they had actually felt during the activity.

The measures of affective forecasting demonstrated that introverts were especially likely to have low predictions of positive emotions when preparing to act extraverted. In addition, introverts were especially likely to have high predictions of negative emotions and self-consciousness when preparing to act extraverted. However, there was little difference between introverts and extraverts on their predictions of how "pleasant" the experience of acting extraverted would be.

Measures of the participants' ratings of their actual experiences demonstrate that all participants who had been assigned to act extraverted experienced more positive emotion and less negative emotion than the participants who had been assigned to act introverted. Additionally, the level of positive emotions was higher and the level of negative emotion was lower than they had predicted beforehand. As well, all participants overestimated how self-conscious they would feel; this was especially true for the participants who were preparing to act extraverted. So we see that both introverts and extroverts had a more positive experience than they thought they would have and that this effect was most pronounced when their behavior was extraverted.

Zelenski et al. compared participants' predictions with their reports of the experience to estimate how accurate introverts and extraverts are in predicting their emotional experiences. They found that introverts were comparatively less accurate: introverts were more likely to overestimate negative emotional reactions and that this was especially true when introverts were planning on acting extraverted. Likewise, introverts were more likely than extraverts to inaccurately over-estimate their degree of self-consciousness when asked to act in an extraverted way.

These findings may have some limitations, as one's experience in a laboratory may be different than in real life. For example, in real life you are not instructed to act introverted or extraverted, although one could argue that acting extraverted may be rewarded in American culture. Another limitation that was not addressed by the authors is that 70% of the participant were women. Past research suggests that women are less likely than men to be introverted, so it is not clear if the introverted and extraverted participants were equally represented by male and female students. If they were, one could ask if the introverted females were somehow different than average females - a question that could influence how well the results would generalize to the population at large.

Nevertheless, Zelenski et al. conclude that part of what may drive Introvert Cat to decline a dinner invitation could be an error in his affective forecasting: he would have enjoyed himself more than he realized. If introverts underestimate the enjoyment and over-estimate the pain of social situations, they may mistakenly say, "no" to experiences that would increase their happiness. On the other hand, this is not to imply that all introverts should try to be extraverts! On the contrary, the authors write:

Despite our speculations about acting extraverted..., we feel compelled to explicitly state that we do not view introverts as inferior or in need of psychological change. (Many of us have pronounced introverted tendencies of our own!) Some introverts might desire the potential happiness boost that an acting extraverted exercise might provide. We believe that studying the potential of such a tool and providing accurate information about its effects may ultimately produce hedonic benefits for some, but we have no interest in forcing it on anyone" (p. 1105)."

Further Reading:

The Zelenski et al. (2013) article can be accessed through your local college library.

Find out if you are an introvert or an extravert by taking this Psychology Today quiz. If you end up scoring in the middle, you may be an ambivert - find out about yourself in this Wall Street Journal article.

Is Western culture biased against introverts? In this TED talk, writer and lawyer, Susan Cain, argues that introverts have overlooked positive qualities that should be valued.

Give In...to Gender Transcendence

If I could be Queen of the World one of my wishes would be for everyone to have the freedom of Gender Role Transcendence meaning that we would each do and like what we are good at and what interests us and not worry if people of our gender or sex are "supposed to" do or like those things in our culture.   One fellow who seems to have achieved this is featured in this week's meme:

This meme is a play on a quotation from "Star Wars:  Return of the Jedi" in which Darth Vader's BFF, The Emperor Palpatine, goads Luke Skywalker by saying, "Give in to your anger."  The humor comes from portraying the Dark Side's most famous General in a stereotypically feminine way:  we associate being emotional (but not being angry); knitting; the color pink; sitting in a closed position; crafting; and the word "pretty" with the feminine gender role.  Since Darth Vader does not seem to care if he is breaking gender stereotypes or not, he is just doing something that he enjoys, we can say that he is showing Gender Role Transcendence.

How would an average man, not a Sith Lord, develop Gender Role Transcendence?  Gender Role Journey Theory proposes that adults move from buying into our culture's gender roles, to having mixed feelings about them, this ambivalence gives way to anger about these roles which can spur actions to fights those roles, and finally transcendence, meaning that they can be whatever mix of those gender roles that suits who they really are (O'Neil & Carroll, 1988).

A recent article by McDermott and Schwartz (2013) used a measure based on this theory to categorize young adult men (ages 18-36) into four groups that represent four stages toward Gender Role Transcendence:  Not Questioning/Accepting of Traditional Gender Roles; Questioning With Strong Ambivalence (confusion and fear); Questioning With Weak Ambivalence (confusion and fear); and Pro-Feminist Activities.  The authors did not find evidence that any of their participants had moved into the final stage of transcendence, but they did discover that the men who were the closest to it - the participants in the Pro-Feminist Activities category - tended to be older.  This suggests that few men in their 20s or 30s are likely to be in Gender Role Transcendence - instead in this sample 70% of the men were Questioning With either Strong or Weak Ambivalence.  However with increasing age we would guess that more of those men would reach Gender Role Transcendence.  True to our meme, the wisdom of the Internet estimates Darth Vader's age at death to be 45; as a midlife man he would be more likely to have reached that state of mind.

The men in the Pro-Feminist subgroup were also more likely to be married or engaged (to women).  This is a classic example of a positive correlation because we do not know what is causing these two traits to hang together.  It could be, as McDermott and Schwartz suggest, that these men, "...may have learned to be flexible in their gender role ideology as part of navigating intimate relationships [with women]" (p. 208).  On the other hand, it may be that viewing women as equals (Pro-Feminist ideology) makes you an appealing partner to women for committed relationships.  It could also be a third variable: most heterosexual adults get married in their late 20s or 30s, so increased age might separately encourage men to view women as equals AND encourage them to get engaged/married.  So we cannot be sure if Darth Vader's marriage to Padmé Amidala was a cause of, a result of, or just a coincidence with his Gender Role Transcendence.

If you - male, female, or anyone in between - are looking to transcend the roles that our culture has assigned to your sex or gender you don't need to have mastered The Force.  My best advice is to just be yourself - which, by the way, does get easier as you get older.  If you need further encouragement, here are a young Michael Jackson and Roberta Flack singing on the 1970s children's television special, "Free to Be You and Me."

Further Reading:

You can access the McDermott and Schwartz (2013) article at your local college library.

A Master's Thesis in Cultural Psychology by John Pianka (2013):  "The Power of the Force: Race, Gender, and Colonialism in the Star Wars Universe."  Darth Vader may have transcended gender in our meme, but gender stereotypes are plentiful in the series.

The Huffington Post ran an article on men and knitting: "Bros and Rows."  This was also published in 2013!

Saying "I love you"...

For this post I have to revert to preschool scatological humor for just a moment...

so if a brief, funny reference to poop is offensive...

read no further.

I have often thought that diarrhea is really the perfect excuse if you want to leave a boring situation.  If anyone tries to stop your departure, whispering, "I have diarrhea," will be the instant get-out-of-jail-free card because everybody has been there and -- for goodness sake -- nobody wants you to stick around in that state.  

With this shared human experience we introduce this week's meme:

When I searched this meme on the Internet I found a curious thing:  like this version starring Optimistic O'Connell, the other versions display a male making this statement.  Ignore the diarrhea part for now - what interested me was that this is a meme of about a confession of love.  And some versions -- like this one -- convey that this confession is being expressed to a female.

Past research suggests that, in heterosexual dating relationships, men tend to tell their partners, "I love you," earlier women do.  A pair of studies by Ackerman, Griskevicis, and Li (2011) confirm that trend, and demonstrate that this reality is the opposite of our stereotype.  Sixty-four percent of college students (who were stopped on a street corner and offered, "candy and juice drinks" (p. 1082) for their insights - I guess that is all it takes...) actually believed that the reverse was true:  that women say "I love you" first.

Ackerman et al. (2011)  includes other laboratory studies about how people feel when their partners just can't hold it in and blurt out "I love you."  Not surprisingly:  they like it.  But does the timing matter and what do we interpret that "I love you" to mean?  Because the authors come from an Evolutionary Psychology point of view, they were particularly interested in the variable of sex.

The authors' final studies determined that men are happiest when their female partners say "I love you," before the relationship has become sexual; women are happiest when that confession of love occurs after sex has been initiated.  This gender difference meshed well with the participants' reported interpretations of "I love you" at different points in the relationship:  men interpreted women's pre-sex "I love you" to mean, "I will probably have sex with you in the future;" while women interpreted a pre-sex "I love you" to mean, "I am trying to convince you to have sex with me."  If instead men's first "I love you" occurs after sex is introduced into the relationship, women interpret that same phrase to mean, "I will stick around for you."

Ackerman et al. invoke Evolutionary theory to interpret these findings.  The basic idea, put forth by researchers such as Buss, is that men have evolved to look for baby-makers - so they would like it if they get the signal that sexual reproduction might be possible.  Women have evolved to look for a mate who will stick around when they are pregnant and nursing babies - so they would like it if they get the signal that a guy is in it for the long-haul and not just looking for one night of reproduction of the fittest.

Evolutionary theory is one way to look at gender differences.  An alternative point of view, Social Role Theory, comes from Eagly and Wood (1999).  They suggest that today's gender stereotypes may have their roots in the long history of men having more power than women.  This inequality came from some biological differences (men are stronger and faster; solely women contend with pregnancy and breast feeding) that gave way to common roles that men and women took on in society.  Seeing thousands of years with more men in leadership positions we still leap to conclusions that all men are better leaders than all women; seeing thousands of years with more women than men caring for children we still leap to conclusions that all women are more nurturing than all men.

So it may be that evolutionary reproductive urges are guiding the timing and interpretation of "I love you."  It could also be that Social Role Theory is guiding these behaviors.  In that case, men's history of greater power and our stereotype of them as being leaders allow them to take more risks in relationships by saying "I love you" first and not being scared off if women say it before sex has occurred.  Likewise, women's history of less power and our stereotype of them as caregivers might encourage them to hold back that "I love you" until they have evidence (like sex) that their partners will be glad to hear this.

At this point we cannot say which perspective is right.  But what you can know for certain is this:  if somebody tells you "I love you," and you don't feel the same way...just tell them you have diarrhea and they will get out of your way.

Further Reading:

A post on a related topic from the Science of Relationships blog:  "Who Falls in Love First"?  This study is also explained using Evolutionary theory; can you imagine how Social Role Theory might interpret the same findings? 

Click here for home remedies for diarrhea and for a broken heart.

You can find a version of this article on Joshua Ackerman's website and obtain the published article through your local university library:  Ackerman, J.M, Griskevicius, V., Li, N.P. (2011) Let's get serious: Communicating commitment in romantic relationships. Journal of Personality and Social Psychology, 100(6),1079-1094.