Effect of fMRI Scan Presentation on Perceptions of Homosexuality

Running head: EFFECT OF fMRI SCAN PRESENTATION 1
Effect of fMRI Scan Presentation on Perceptions of Homosexuality
Whitney Russell, Jacob Wilson, Walter Smith
Austin College
Author Note
Whitney Russell, Department of Psychology, Austin College; Jacob Wilson, Department
of Psychology, Austin College; Walter Smith, Department of Psychology, Austin College.
Correspondence concerning this article should be addressed to Whitney Russell, Jacob
Wilson, Walter Smith, Department of Psychology, Austin College, Sherman, TX 75090. Email:
wrussell11@austincollege.edu, jwilson10@austincollege.edu, wsmith09@austincollege.edu

EFFECT OF fMRI SCAN PRESENTATION 2
Abstract
The primary purpose of the present study was to see if exposure to more critical thinking classes
would affect how much influence an article about a controversial topic had when intertwined
with an fMRI scan. Recently fMRI scans have been a very popular topic in the media. McCabe
and Castel (2008) found that brain images can persuade individuals to accept information more
easily than articles that do not contain brain images. In our study, an article on the biological
basis of homosexuality was given to participants to read. In the first condition, participants only
read the article. In the second condition, participants read the article and were given a bar graph
that represented the data. In the third condition, participants read the article and were given an
fMRI scan and bar graph to represent the data. There was a significant difference in agreement
for the biological basis of homosexuality depending on the article condition the participants were
placed in, F(2,57) = 3.86, p < .05. Participants who received the bar graph and fMRI images with
the article rated homosexually as significantly more biological than the participants in the
graph/article condition, p < .05. We also found that participants with a Science major agreed that
homosexuality was biological more so than non-science majors [t(58) = 2.86, p < .05] and
reported a greater change in their opinion of homosexuality after reading the article [t(58) = 3.11,
p < .05]. When participants scored high on scientific reasoning, they were also more likely to be
influenced by the material in the article regardless of condition. Together, this research suggests
that opinions concerning the biological basis of homosexuality can be changed with exposure to
research, and in some case the use of fMRI images is more persuasive.
Keywords: homosexuality, biological, fMRI, critical thinking, perception, influence

Effect of fMRI Scan Presentation on Perceptions of Homosexuality
On a frequent basis, scientific information is displayed by means of visual aid in order to
facilitate the viewer’s understanding. The use of images, tables, and graphs all help to build
support and credibility in regard to scientific topics. This is usually dependent on the amount of
critical analysis that the viewer places on the information that they are being asked to believe.
This is becoming even more pertinent as advancements in neuro-imaging technology (viz.,
functional magnetic resonance imaging (fMRI)) are made. Due to the physical representation of
information that brain imaging features, some suggest that images of brain scans are typically
considered more credible than the less tangible information within text, tables, and graphs.
Researchers have found that people are more likely to believe what a research article says if there
is an fMRI scan backing up what the article is saying (McCabe & Castel, 2008). Can this,
however, alter the perceptions of people regarding issues as controversial as homosexuality?
Furthermore, what difference does an education in psychology make on these perceptions and
are they swayed as easily as a person with no background in the sciences? The purpose of the
current study is to examine the effect of fMRI scans on reasoning and impact that taking
psychology classes has and answer these questions. We will test this by using three different
versions of an article to act as the independent variables (one article with only words, one article
with a bar graph, and one article with a bar graph and an fMRI scan). The article will be
discussing the scientific basis of homosexuality.
According to research, the influence of fMRI scans can make such a substantial impact
that opinions on very controversial issues can be manipulated. Weisburg (2008) points out
certain drawbacks to people becoming more familiar and conditioned towards the use of fMRI
and PET scan images in the popular media. She implies that they could potentially convince
people of poor science having validity. An example could be misuse of neuro-imaging by a

careless science writer or neuro-image use as misleading evidence in courts. For example,
McCabe, Castel, and Rhodes (2011) presented participants acting as mock-jurors in a murder
case with one of six different evidence conditions (the control, polygraph, fMRI, thermal
imaging (TI), fMRI: validity questioned, TI: validity questioned). In all conditions, the evidence
was not necessarily strong enough to suggest that the defendant was guilty of murdering his wife,
but each participant was to state their personal verdict and which form of evidence was the most
influential in their decision. Results indicated that the fMRI lie detection readings were not only
the primary decision-making influence, but they also resulted in the largest number of guilty
verdicts compared to the five other evidence conditions. This finding supports the notion that
fMRI scans can occasionally be too persuasive in decision-making.
McCabe and colleagues’ (2011) study was challenged by Schweitzer et al. (2011). In
their study, four simulated trials were sent to participants via Internet. These included a summary
of the case at hand, the evidence, and the experimental manipulation (a collection of expert
evidence and neuro-images). The participants were to act as jurors and come to a verdict on the
case. If they decided “guilty”, they were to recommend a punishment for the convicted. The
participants then completed a survey assessing the trial and specific elements of their testing
experience. Each of the control conditions resulted in a failure to recognize a significant
difference between the neuro-images and any of the other neurological-based conditions. All
four experiments consistently failed to obtain any effects of neuro-imagery on the jurors’
decisions regarding their verdict and their sentence suggestion. This suggests that judgment on
controversial issues cannot be genuinely dominated by brain images and that fMRI scans may
not be making the immensely impactful persuasion that some have come to believe. In the
present study, the participants that we survey are our “jurors”, and we will present them with our
“evidence”: an article discussing the biology of homosexuality. According to McCabe et al.

(2011), the inclusion of brain images within the homosexuality article will make a significant
impact on our participants’ survey responses. Schweitzer et al. (2011) poses the competing
suggestion that our participants will not be significantly influenced by the images within the text.
Neuropsychological research fascinates much of today’s public. Many people tend to
accept statements and explanations that include a high level of psychological material without
actually taking the time to critically analyze what it is they are being asked to believe (Weisberg,
Keil, Goodstein, Rawson, & Gray, 2008), simply because it seems legitimate to a naïve audience.
Keil, Lockhart, and Esther (2010) ran a study looking at how the different fields of Psychology
are viewed. Neuroscience was seen as the hardest among all the age groups in the study. If there
is a particular reason that neuroscience is foreign to so many people, it might explain why they
grasp to an image that attempts to explain it. Time and time again, we as a society, accept
something we are told simply because it seems scholarly or highly intellectual. When people
read an article full of neuroscience and advanced psychological information, they assume that the
researcher knows what they are talking about and are completely valid in their statements.
Advanced terminology sounds impressive, complex figures and images are rousing, and it is
easier to trust this material than it is to cognitively break it down and reason with it.
Lindström (1996) says that there are two main ways to attempt to change someone’s
opinion: theory-related and data-related persuasion. Data-related persuasion deals with
presenting empirical evidence in an attempt to expose a cognitive incontinency with previous
beliefs. His study found that with empirical evidence, people would be more likely to consider
differing opinions, even if it does not change their own. Without this evidence, it would be very
unlikely another person would even consider the opposing opinion to be plausible. As one would
expect, a reader’s comprehension level of empirical evidence hinges heavily on their ability to
scientifically reason with it. According to studies on the Conceptual Change theory, the more

education in the sciences that a person receives, the more that those scientific reasoning abilities
will be ingrained within their mind (Amsel et al. 2008). Therefore, it would make sense that
psychology students who have learned to think critically and reason with a statement’s validity
would be more apt to sift through “smart-sounding” terminology and misleading images and
recognize poor articles with weak explanations.
Researchers have discovered that, surprisingly, the effect of the Conceptual Change
theory is not always present (Mill, Gray, & Mandel, 1994; Weisberg et al., 2008). Weisberg and
colleagues conducted an empirical study that consisted of three experiments (novice group,
psychology student group, and neuroscience expert group) based on a 3 2 2 (good vs. bad
explanation neuroscience present vs. absent) design to display the subjects’ ability to
differentiate between strong and poor explanations of phenomena, regardless of the presence of
neuro-scientific information. Results showed that only neuroscience experts were able to
consistently see through the allure of unessential information and critically distinguish which
explanations of phenomena were strong and which were not. Taking into consideration that most
people are not experts in the field of neuroscience, it is plausible that a statement built off of any
neuro-scientific explanation could potentially sway the perceptions of the general population.
This idea is applicable in the present study because we will be having our subjects read articles
that are infused with neuroscience and biological explanations of homosexuality. All of our test
subjects will be college students who have taken anywhere from a few to zero psychology
classes, and according to the study by Weisberg et al. (2008), the article should by and large
persuade them.
In recent times, the topic of homosexuality has come to a forefront. There are political,
legislative, ethical, religious, and emotional battles over how homosexuality should be viewed.

Lately, there have been great strides in the research and understanding of the homosexual mind.
Coghlan (2008) suggests that the brain activity of a homosexual male can sometimes mirror the
brain activity of a heterosexual female, and the activity of a homosexual female will sometimes
mirror the brain activity of a heterosexual male. Delving even deeper into this idea, it has a been
discovered that homosexual men and women respond to putative human pheromones (4,16-
androstadien-3-one and estra-1,3,5(10),16-tetraen-3-ol) in the same way that heterosexuals of
their opposite gender do (Savic, Berglund, & Lindström, 2004; Berglund, Lindström, & Savic,
2006). Brain scans can even observe the comparisons of brain activation between heterosexuals
and homosexuals. Savic and Lindström (2008) used PET and fMRI scans in a study to examine
exactly what occurs within the brain regarding sexual orientation. Their discovery that activation
of the amygdala within homosexual men resembles that of heterosexual women, and vice versa,
was so compelling that we merged it with Simon LeVay’s article, “The Paradox of Gay Genes,”
to create a stronger biological explanation of homosexuality. In our present study, this
compilation is what we will be using as our stimulus article. A major aim of our study is to
identify effective techniques of informing the general public of the biological origins of
homosexuality. This in turn could potentially help reduce homophobic prejudice throughout
society. The professional world and modernized pockets of society have begun to ensure a level
of equality between hetero- and homosexuals. With official attitudes of homosexuality having
shifted closer to a level of acceptance, Landén and Innala (2002) conducted a study to recognize
if the perceptions of the general public have changed as well. While 18 percent of their 668
respondents believed that homosexuality is a curable disease, about half of the respondents
believed that homosexuality has a biological explanation. Over half of the respondents felt that
gays and lesbians should have the rights of marriage and adoption. Landén and Innala’s study
suggests that over the past decade, due to a spread in knowledge and anti-discrimination laws,

the general outlook on homosexuality has grown more tolerant. Although this study took place in
Sweden, it is still comparable to the United States in regards to social ideas and general public
attitude. As Landén and Innala’s study suggests, males and older people tend to hold on to more
socially conservative values than younger people and females who are more tolerant. If our
research data coincides with what Landén and Innala’s article suggests, then I suspect that the
majority of the young participants in our study will come in with the preconception that
homosexuality is acceptable. The pivotal factor that our study will include that Landén and
Innala’s did not, however, is the neuro-scientific stimulus article and brain images that we will
be attaching. Perhaps this will create a considerable amount of persuasion towards the
acceptance of the biological explanation of homosexuality.
The article that we will have our test subjects read will have a strong explanation backed
with neurological support. Despite this, it is unknown if this information alone will be able to
outweigh and persuade any preconceived notions that our subjects have formed about
homosexuality. Therefore, we will test our subjects with various forms of support (i.e., text, bar
graph, and fMRI scan). Taking into account past research and the findings of McCabe & Castel
(2008), we hypothesize that the article with both the bar graph and fMRI will be the most
influential. In correspondence with the Conceptual Change theory and the research conducted by
Amsel et al. (2008), we hypothesize that underclassmen and/or non-science majors will be more
influenced by the neuro-images than students who are science-based majors.
Method
Participants
60 undergraduate college students of at least 18 years old were recruited through the
Austin College Psychology Department participant pool. Average participant age was 20.28
years. There were 33 males and 27 females. They were offered extra credit in compensation for

their participation. All participants were treated in compliance with American Psychological
Association and Austin College Institutional Review Board ethical standards.
Materials and Procedure
The subjects entered the lab and, after filling out the informed consent form, were given a
simple demographic survey asking for their age, school classification, gender, major, minor, and
history of psychology courses. After the survey, each participant was told that they are about to
be given an article about a controversial topic to read. They received one of three versions of
Simon LeVay’s article entitled, “The Paradox of Gay Genes,” to read. We selected this article
because it was compiled with neuro-scientific material and expert information on the biology of
homosexuality. These three article versions acted as our three different conditions. The first
condition was a version of the article that had no images (text only). The second condition was a
version of the article that includes a bar graph depicting the levels of left amygdala activation in
heterosexual men and women and homosexual men and women. The third condition was a
version of the article that featured both the bar graph and an fMRI scan. The fMRI scan depicted
the left and right amygdala activation in heterosexual men and women and homosexual men and
women (see Appendix). Once the participants were finished reading the article, they were given
another survey that had several questions about how the article was written, what they thought of
it, how well it was justified, and what their perspectives on homosexuality were. These questions
were asked using an interval scale from 1-6 (1 being “strongly disagree” and 6 being “strongly
agree”). We chose to use an even number scale in order to prevent the subjects from answering
directing in the middle. This whole process took each participant an average about 15 minutes to
complete.
Results

The effect of the article condition type (text, graph, and fMRI) and the classification year
of the participant (freshman, sophomore, junior, senior) was examined by calculating One-way
ANOVA. There was a significant difference between the article condition assigned and how they
answered the after article survey questions pertaining to the biological concepts of
homosexuality, F(2, 57) = 3.59. Post-hoc analysis indicated that fMRI condition participants
scored significantly higher at biological concepts of homosexuality than the graph-only condition
participants, p < .05 (see Figure 1). There was no other significant difference between article
type or classification year (freshman – senior) and how they answered any of the other questions,
all p > .05.
We ran multiple t-tests to examine the statistical significance between an independent
variable with two levels and many dependent variables. There was no significant difference
between the gender of the students and how they answered the questions, all p > .05. There were
27 participants who had majors within the sciences (Chemistry, Biology, Physics, Psychology)
and 33 who did not. Participants that were majoring within the science department had higher
scores on the biological concepts of homosexuality questions, t(58) = 2.86, p < .05, and the
influence that the article had on their opinions of homosexuality, t(58) = 3.11, p < .05 (see
Figure 2). Surprisingly, there was no difference across majors in the rating of the article’s level
of scientific reasoning. There were 17 participants who had taken Biological Psychology
(BioPsych) and 43 who had not taken it. Students who had taken BioPsych rated the scientific
reasoning of the article higher, t(56) = 2.09, p < .05, scored higher at the biological concepts of
homosexuality, t(56) = 2.71, p < .05, and their opinions of homosexuality were more influenced
by the article, t(56) = 1.97, p < .05 (see Figure 3). There were 19 participants who had taken
Research Methods and 41 who had not. There was no significant difference between participants
who had taken and had not taken Research Methods and how they answered the questions, all p

> .05. We grouped freshman and sophomores into one group (underclassmen, N = 23) and the
juniors and seniors into another group (upperclassmen, N = 37). Upperclassmen were
significantly more likely to state that homosexuality has a biological basis than underclassmen,
t(56) = 2.04, p < .05. This indicates that underclassmen are more likely to consider
homosexuality a choice.
We ran a correlation between the number of psychology classes taken by our participants
and the dependent variables from our post-article survey. We found that as participants agreed
that homosexuality is biological, their score on the questions concerning the biological basis of
homosexuality increased, r(59) = .80, p < .05. This relationship suggests participants were
attentive, genuine, and understanding of the questions, providing for reliable responses. As
participant understanding of the article increased, the score of the scientific reasoning questions
also increased, r(59) = .47, p < .05. When participants rated the article’s scientific reasoning
higher, they also stated that they had a greater change of opinion concerning homosexuality,
r(59) = .46, p < .05. The more psychology classes a participant had taken, the more the article
changed their opinions in regard to homosexuality, r(59) = .29, p < .05.
When asked the open-ended question, “which piece of information was most influential,”
nearly 50% of the participants provided responses pertaining to the fMRI and brain differences
(see Table 1 for complete qualitative results). Our qualitative data showed that participants who
were in the text-only condition were most likely to list brain differences as the most influential
piece of information. The bar graph-only condition listed brain scans most often. Surprisingly,
the fMRI condition listed the outside study citation as most influential more often than anything
associated with the brain.
Discussion

We attempted to examine the level of influence of different forms of information
representation on students’ perception of homosexuality. We did this by providing them with a
stimulus article based on the biological connections to homosexuality. To create more testing
conditions, we supplemented the article text with either a bar graph representing brain activation
within the amygdala or the bar graph and an fMRI brain scan depicting left and right amygdala
activation. Our findings suggest that viewing fMRI scans increases understanding and
acceptance of the biological basis of homosexuality. As we expected, the participants that were a
part of the fMRI condition agreed more with the biological perspective than the text-only and
graph conditions. On the other hand, it was interesting to see that the graph-only condition rated
lowest in the biological concept category. We expected for the graph-only condition to have a
biological concept score that falls between the text-only and fMRI condition scores, but that was
not the case.
As one would expect, we found that science majors tend to accept the biological basis of
homosexuality much more often than non-science majors. To our surprise, however, science-
majors did not score much higher at the scientific reasoning portion of the survey than non-
science majors. One of the most noteworthy variables in our study was the course, Biological
Psychology. Participants who had taken BioPsych had distinctively greater biological
perspectives of homosexuality, underwent more influence of opinion, and had higher levels of
scientific reasoning. The Research Methods course, on the other hand, yielded results that were
much less impressive. This could be due to Research Methods not teaching the functions of the
brain like BioPsych does. BioPsych goes into more depth about neuroscience than the majority
of courses offered at the undergraduate level. Therefore, students that have taken the class should
have a strong insight as to how the brain works. Students of Research Methods do not learn a
great deal about brain functions, but they do receive an ample amount of training in critical

thinking and scientific reasoning. Due to this training, it was unanticipated that these participants
did not score higher at the scientific reasoning portion of the survey. When the participants were
asked, “Do you think homosexuality is biological or a choice,” upperclassmen typically
responded with “biological” and underclassmen with “choice.” This trend is simply explained by
the fact that as students spend more time in college, they have more opportunity to take courses
within the science field. Also, upperclassmen have taken more advanced science, psychology,
and critical thinking classes. Hence, they have a greater scope of knowledge concerning the
human mind, thought processing, and functions of the brain. Experience in college also plays a
hand in whether or not a particular student has taken BioPsych or not. BioPsych is not a
beginner’s course so naturally most underclassmen have not yet taken it. Consequently, a
sizeable portion of our BioPsych participant group was upperclassmen.
As participants agreed more with the biological basis of homosexuality, their scores for
understanding the biological concepts of homosexuality increased. This is logical because the
better someone understands the biological explanation of homosexuality, the more likely they
will be to accept it as the truth. Those who cannot grasp the biological concepts of
homosexuality obviously have a higher probability of considering homosexuality a choice. The
correlation between how well the participants understood the article and the participants’ rating
of the article’s scientific reasoning indicated a positive relationship. Critically thinking
participants may have been more capable of breaking the down the text of the article, processing
the information effectively, and assessing the article’s scientific reasoning. Also, participants
who are more skilled at critiquing scientific reasoning may have had previous experience and
practice at analyzing scientific articles during their studies, resulting in a superior understanding
of “The Paradox of Gay Genes.” Our study also indicated that a higher rating of the article’s
scientific reasoning corresponded with a greater change in opinion of homosexuality. Hence, if

an explanation for phenomena is deemed legitimately reasonable, the reader will likely accept it.
It could also be that participants who possess a strong ability to reason were able to weigh out the
stimulus article’s neuro-scientific information, recognize new ideas, and willingly accept a new
perspective. This could even suggest that those who are more skilled at cognitive reasoning are
more open-minded people. We also observed a positive correlation between changes in opinion
of homosexuality and the number of psychology classes taken. In rejection of our initial premise,
the more psychology classes that participants had taken, the more their opinion changed. In
correspondence with the Conceptual Change theory and the research conducted by Amsel et al.
(2008), we hypothesized that the article would have more influence on underclassmen and
students with less science/psychology experience. To our surprise, we found that the more
history that students had within the science and psychology departments, the more the stimulus
article swayed their opinions. We suspected that the more class experience learning about the
brain would result in students already having a biological opinion of homosexuality solidified.
Perhaps the more experience in psychology classes allowed for a better understanding of what
the stimulus article was about, resulting in a more pertinent influence on the reader.
As previously stated, the fMRI condition yielded survey answers that tended to agree
with the biological perspective of homosexuality, and the fMRI condition subjects also reported
having the highest ability to understand the article. Despite these trends, the fMRI condition’s
level of influence was still lower than we expected. The majority of previous literature would
suggest that the fMRI condition group should have a higher level of scientific reasoning than
what we have found. In order to gauge the level of scientific reasoning, we asked the questions,
“How well written was the article,” “How well was this study carried out,” and “How well is the
conclusion justified.” Our findings echoed the results of Schweitzer et al. (2011). As outlined
previously, their study failed to recognize any noteworthy difference between the neuro-images

and any of the other neurological-based conditions in each of their control conditions. While our
study may concur with the findings of Schweitzer et al., it does not support the major breadth of
past literature suggestive of the large impact that neuro-imaging has on viewer perspective.
Therefore, we were surprised to not observe the same substantial results that were observed by
McCabe and Castel (2008) in regards to scientific reasoning.
While this area of study may require further exploration, our findings provoke several
thoughts. The present study only surveyed college students, and it would be ideal to expand this
study to a broader range of participant ages. Thus, we could observe the differences between
generations in perception of homosexuality and influence of neuro-imaging. Expanding the
participant group into various demographic, geographic, cultural, economic, and familial
backgrounds would also yield some interesting information that should eventually be looked
into. A weakness of our study is that we lacked the ability to collect completely genuine
responses from all of our participants. Some participants may not have fully read the stimulus
article, or they could have selected random survey answers in order to finish the experimentation
process quickly. We attempted to eliminate the “fence-sitter” participants by providing an even
amount of interval answers. Nonetheless, participants may still have answered “3” or “4” on the
scale from 1-6 in order to take the easy way out and give moderate responses. Also, some
participants may have given answers that were not completely genuine in attempt to appear
unprejudiced. Often times people, especially young men, struggle to balance their unprejudiced,
heterosexual appearance while coping with internal homophobia in social interactions (Korobov,
2004). In his study, Korobov observed 54 adolescent males for over 300 hours and found that
most subjects alter their actions and statements in order to appear more righteous. What Korobov
suggests is useful to the present study because it addresses the possibility that our test subjects
did not answer our homosexuality survey truthfully. It is a concern that the participants chose to

provide more homosexually tolerant responses than they typically would think to themselves
simply because they would not want to appear homophobic. The validity of our data could be
altered if our participants were not genuine in all of their survey responses. This is why is was
imperative that the test subjects were aware that their answers will be kept confidential and used
strictly for data analysis and research purposes only.
From what we have gathered in this study, the most effective techniques in
communicating the biological explanation of homosexuality is to provide neuro-scientific
material in a visual fashion like brain scans, enroll students in BioPsych, and providing students
with a science-major course-load. Since the last option is far from practical, the use of fMRI
scans should be more widely utilized when presenting information on homosexuality, and
students should strongly be encouraged to take BioPsych. Regardless of what major a particular
student is, most undergraduate programs require at least one science course, and BioPsych would
be an excellent option. The present study indicates that it makes a large impact on students’
scientific reasoning and their understanding of the biological concepts of the brain. If every
student took BioPsych at some point in his or her undergraduate career, society’s overall
perspective of homosexuality would potentially make an immense swing towards the biology-
based belief. When future studies over homosexuality are published, when advocacy posters are
made, and when other awareness efforts are carried out, fMRI scans should be included. Tacking
brain scans on adds another dimension to the message being conveyed and produces a concretely
visual dynamic for viewers to absorb. When taking the present study into consideration and
looking forward to future directions, we must remember that people comprehend concepts in
different ways, and the use of brain scans can only aid in the education of the masses.

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Appendix
“The Paradox of Gay Genes”
Brain scans reveal that in gay people, key structures of the
brain governing emotion, mood, anxiety and aggressiveness
resemble those in straight people of the opposite sex. The
differences are likely to have been forged in the womb or in early
infancy, says Ivanka Savic, who conducted the study at
the Karolinska Institute in Stockholm, Sweden.
Savic and her colleague, Per Lindström, chose to measure
brain parameters likely to have been fixed at birth. "That was the
whole point of the study, to show parameters that differ, but which
couldn't be altered by learning or cognitive processes," says Savic.
First they used MRI scans to find out the overall volume and
shapes of brains in a group of 90 volunteers consisting of 25
heterosexuals and 20 homosexuals of each gender. The results
showed that straight men had asymmetric brains, with the right
hemisphere slightly larger - and the gay women also had this
asymmetry. Gay men, meanwhile, had symmetrical brains like
those of straight women. The team next used PET scans to measure
blood flow to the amygdala, part of the brain that governs fear and
aggression. The images revealed how the amygdala connected to
other parts of the brain, giving clues to how this might influence
behavior.
They found that the patterns of connectivity in gay men
matched those of straight women, and vice versa. In straight
women and gay men, the connections were mainly into regions of
the brain that manifest fear as intense anxiety. In straight men and
lesbians, the amygdala fed its signals mainly into the sensorimotor
cortex and the striatum. If being gay is genetic, and gay sex doesn't
produce children, why don't those genes die out?
That's a sensible question, said Simon LeVay, Ph.D.,
the author of Gay, Straight, and the Reason Why: The Science of
Sexual Orientation, and one to which we don't yet have a crystal-
clear answer. In the case of homosexuality, most estimates
(derived from twin studies) are that genes account for no more than
about half of the total causation of this trait. The remaining causes
include hormonal factors operating during fetal life -- factors that
may not be under genetic control.
The key to understanding how gay genes survive is the
realization that such genes exist, not only in gay people
themselves, but also in some of their non-gay relatives. For
example, the sisters of a gay man might have inherited the same
gene that he did, but because different genes are thought to
promote homosexuality in men and in women, this 'gay male gene'
won't make them lesbian. If the gay man helps his sisters raise
more children than they would otherwise be capable of, then the
decreased reproductive success of the gay man might be more than
compensated by an increased reproductive success of his sisters,
and it would be they, not he, who pass the gene on to the next
generation. This is the so-called 'kin selection' hypothesis.
Some support for this hypothesis comes from studies
conducted in Italy and in Britain, which have found that women
with gay male relatives -- and who might therefore carry a gay
male gene, do have significantly more children than women with
no such relatives. This effect was seen even for women whose gay
male relatives cropped up in a later generation, so that the men
were not in a position to provide any material assistance to those
women when they were having children. Still, there are also
studies that fail to find this effect, so it's not yet clear whether it
could be a general mechanism for the persistence of gay genes.
Yet another idea is that it's the same-sex relatives of
gay men who enjoy a reproductive advantage. How would that
work? According to economist Ed Miller of the University of New
Orleans, several genes are floating around in the gene pool that
make men more feminine in a variety of respects. Men who happen
to inherit one or two of these genes are still heterosexual, Miller
suggests, but their mild femininity -- which shows itself in the
form of decreased aggressiveness, greater empathy, and the like --
makes them more attractive to women, and thus able to have more
children, as compared with straight men who lack such genes.
When more than two or three such genes happen to end up in the
same man, the process of feminization increases to the point that it
includes sexual attraction to males -- that is, it makes their owner
gay. Such a model is certainly consistent with the observation that
gay men are, on average, considerably more feminine that straight
men in a variety of psychological traits.
According to a research group led by Brendan Zietsch
of the Queensland Institute of Medical Research, feminine straight
men do have more female sex partners than more masculine men
do. Thus the positive effect of feminizing genes on the
reproductive success of straight men could outweigh their negative
effect on gay men. Similarly, Zietsch's group found that
masculinity in straight women is associated with a larger number
of male sex partners, suggesting that Miller's hypothesis could
explain the persistence of lesbian genes too.
Some physical attributes of the homosexual brain resemble
thosefoundin the opposite sex. This chart shows the left
amygdala activation in heterosexual men and women (labeled
HeM and HeW) and homosexual men and women (labeled HoM
and HoW).
Some physical attributes of the homosexual brain resemble
those found in the opposite sex. These images show the
amygdala in heterosexual men and women (labeled HeM and
HeW) and homosexual and women (labeled HoM and HoW).
(Image: National Academy of Sciences, PNAS)
HeM HeW HoM HoW
High
Low
L Amygdala Activation
L Amygdala
Activation

Figure 1. Shows the effect of article type on the score of biological concepts of homosexuality.
The higher the score, the more they agreed with homosexuality being biological. Oneway
ANOVA revealed a significant difference in opinions about homosexuality and article type.
Post-hoc analysis showed that the difference was between fMRI articles and bar graph-only
articles. Those who read the article with the fMRI were more likely to state that they viewed
homosexuality as biological than those who read the article with the graph, p < .05.
0
2
4
6
8
10
12
14
16
18
20
Text Graph fMRI
MeanBiologigalBasisofHomosexualityScore

Figure 2. Shows the effect of being a science or non-science major on the score of biological
concepts of homosexuality and degree of opinion change towards homosexuality. An
independent samples t-test indicated that science (Chemistry, Biology, Physics, Psychology)
majors were more likely than non-science majors to view homosexuality as biologically based
after reading the article, p < .05. Science majors were also more likely than non-science majors
to have their opinions influenced by the article, p < .05.
0
2
4
6
8
10
12
14
16
18
20
Biological Concepts Opinions
MeanScore
Science
Non-Science

Figure 3. Participants who had taken Biological Psychology (BioPsych) were more likely to
have their opinions influenced by the article than participants who had not taken BioPsych,
p < .05. Participants who had taken BioPsych also scored higher on the questions pertaining to
scientific reasoning and were more likely to agree with the biological basis of homosexuality,
p < .05.
0
2
4
6
8
10
12
14
16
18
20
22
Biological Concepts Opinions Scientific Reasoning
MeanScore BioPsych
No BioPsych

Table 1
Most Influential Piece of Information by Article Condition
Article
Type Brain Scans
Brain
Difference Studies Genes Graphs Other/Blank
Text-only 15.00% 40.00% 20.00% 10.00% 0.00% 15.00%
Graph 45.00% 15.00% 15.00% 0.00% 5.00% 20.00%
fMRI 10.00% 20.00% 25.00% 0.00% 25.00% 20.00%
Average 23.33% 25.00% 20.00% 3.33% 10.00% 18.33%
Note. The table displays the qualitative data from the question, “What piece of information was
most influential?” The percentages for each article condition and overall averages are shown.
The Brain Scans category is any response that specifically mentions the PET or fMRI scans. The
Brain Difference category is a participant that mentioned biological differences in the brain
without mentioning the brain scans. The Studies section is an answer that contained one of the
studies, or a theory presented by the study. The Genes section is whenever a participant
specifically mentioned a genetic basis. The Graphs section is whenever a response was about the
added graphs. The Other/Blank category consists of 1) Responses deemed incomplete or unable
to be represented, and 2) Seven participants who left the question unanswered.

Effect of fMRI Scan Presentation on Perceptions of Homosexuality

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