Available online at:
https://cc.arcabc.ca/islandora/object/cc%3Apsycjournal

J Camosun Psyc Res. (2021). Vol. 3(1), pp. 49-60.
Submitted Fall 2020; accepted July 2021.

What Are the Biopsychological Mechanisms of Human
Sexuality?
Authors: JayCee Constantine*
Supervising Instructor: Michael Pollock, Psyc 215 (“Biological Psychology”)
Department of Psychology, Camosun College, 3100 Foul Bay Road, Victoria, BC, Canada V8P 5J2
*Corresponding author email: jayceejoyce@hotmail.com

ABSTRACT
In this paper I explored the biological basis of human sexuality including sex drive and sexual
orientation in order to assist people with learning about their own sexuality, and how sexual
identity and preference is linked to biological mechanisms. Studies have found that hormone
levels, such as testosterone, influence our sexuality, that physical sexual arousal can affect our
subjective sexuality and cause us to make sexual behavioural choices we wouldn’t make when
unaroused, and that there are physical differences in the brain’s amygdala between homosexual
and heterosexual brains. In my first (correlational) study, I tested the strength of these
relationships by examining naturalistic daily changes in their variables longitudinally over a twoweek period. I measured the level of testosterone using a period tracking app, physical arousal
using a set scale, amygdala activity through the heartbeat, and the amount of sexual activity with
journal entries. Data in this correlational study showed significant correlations of sexual activity
with testosterone level, physical arousal, and amygdala activity. Based on the strength of
correlation found between physical arousal and sexual activity, I then conducted a second
(experimental) study to test for specifically a causal relationship between these two variables.
Over a two-week period, on alternating days the participant was assigned to either a high
physical arousal day (watching pornographic videos) condition or a low physical arousal (no
pornographic videos) condition and the effect this had upon sexual activity that day was
measured. The results from the experimental study failed to find a causal role of physical arousal
on sexual activity. A possible practical application of the current findings are the ability to know
best when to engage in sexual activity to get pregnant, though the true cause of human sexuality
still remains to be discovered.
1. Introduction

1.1 Research Problem
Human sexuality has become a central
topic in the last decade, yet we still have an
insignificant amount of information about it.
We need to learn where our sexuality comes

from and what influences it, whether
genetics or otherwise. Our sex drive
influences our everyday decisions and
actions; we need to be aware of how our
animalistic drive governs our lives. Sexual
preference, and orientation, is progressing in
today’s society and it is finally giving us a
chance to study why our sexual preferences
are what they are. Sexuality is something an
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abundant proportion of the world’s
population will struggle with at one point or
another in their lives, and the more we know
about sexuality the better we can assist the
people in our society.
1.2 Literature Review
Hormones, testosterone and others, have
been shown to affect our sexuality and how
strong it is. Van Goozen, et al. (1997)
studied how different hormones in the
female menstrual cycle effect how strong
you react to males and their sexuality. They
followed a number of women across one of
their menstrual cycles, testing their hormone
levels regularly and keeping track of their
sexual contact. Higher levels of both
intercourse and masturbation were recorded
across the ovulatory phase. The women were
also shown to take charge in their sexual
encounters more often in the ovulatory
phase as well. The study concludes with data
from the hormone tests, which shows higher
hormone levels, testosterone, progesterone,
cortisol and more, in the ovulatory phase
especially in those who did not have any
premenstrual complaints or issues. This
study shows that women’s hormones are
responsible for their sexuality and sexual
interest.
Sexuality has to start somewhere, and it
could start in the prenatal environment.
There could be many things that influence it,
but a study done by Reinisch, et al. (2017)
suggests that one of the many things that
influences our sexuality is the prenatal
environment. Children who had
progesterone, a drug that has been regularly
given to expectant mothers to prevent
miscarriages (pp.1241), given to them in the
prenatal phase were less likely to self
identify as heterosexual and more likely to
be involved in non-heterosexual behaviours
(pp.1245). This study shows how important

environmental influences are to the
development of our sexualities even as early
as the first trimester of our prenatal lives.
Our genetics also play a roll in our
sexuality. Sanders et al. (2015) conducted a
massive study looking for a genetic link to
homosexuality in males. The study looked at
DNA samples from 908 family members,
793 homosexual brothers, 33 heterosexual
brothers, 49 mothers and 33 fathers (pp.
1381). The DNA results showed a strong
linkage from male sexual orientation to
chromosome 8 and a few other spots in our
DNA (pp.1384). These results point
significantly to a genetic connection to
sexual orientation. We might not know yet
what exactly contributes towards sexual
orientation, but we are getting closer with
every study of genetics.
Our physical sexual arousal can affect our
subjective sexuality. A study done by Ariely
& Loewenstein (2006) involving 35 male
university students found that men reported
things to be attractive while in a state of
arousal that they would not have reported in
a state of non-arousal (pp. 93). When
aroused, the males in the study reported they
were more likely to engage in date-rape
behavior including encouraging a woman to
drink more or even drugging her if it meant
the outcome was sex (pp. 94). While this
study had its limitations, it shows a clear
biopsychological connection between our
physical sexual arousal and our sexual
behavioural choices.
Sexual preference can be seen in the
brain. Savic & Lindström (2008) performed
a study that looked at the brain’s responses
to sex pheromones in homosexual and
heterosexual subjects. PET scans and MR
images were used to compare the asymmetry
in the participants’ brains. Similarities in the
amygdala, the part of our brain that deals
with emotions, were found in homosexual
men and heterosexual women as well as
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heterosexual men and homosexual women.
This study shows us that there is a link
between the part of our brains that is
genetically different due to our sexual
characteristics and our sexual orientation.
This study and its findings will hopefully
encourage a closer look into the
biopsychological mechanism of human
sexuality.
1.3 Hypotheses
Based on the above literature review, we
predicted the following hypotheses:
 Hypothesis #1: If testosterone levels
increases then sexuality increases.
 Hypothesis #2: If physical sexual arousal
increases then your subjective sexuality
increases.
 Hypothesis #3: If brain activity increases
in the amygdala then sexuality increases.
2. Methods
2.1 Participant
The author of this paper served as the
participant in its studies. The participant is a
23 year old cis gendered female. The
participant was an undergraduate student at
Camosun College who completed the
current studies as an assignment for Psyc
215 (“Biological Psychology”).
2.2 Materials and Procedure

2.2.1 Correlational Study Methods
I first performed a correlational study to
test concurrently all three of the hypotheses
by examining naturalistic daily changes in
their variables longitudinally. The
participant kept a study journal with her at
all times over this study’s two-week period

in order to record self-observations of the
following three variables: (1) testosterone
level, (2) physical arousal, (3) amygdala
activity, and (4) sexual activity.
To measure the level of testosterone, the
participant kept track of her menstrual cycle.
The ovulatory phase, about the 14th day of
the cycle, is where testosterone is the
highest. The participant used a period
tracking app, called Clue, on a cell phone
which calculated approximate ovulatory
phase after the input of 1 cycle (see
Appendix A). The first day of the menstrual
cycle was counted as testosterone level 1
and then count up to the ovulation day,
testosterone level 14, and then counted back
down to the last day of the menstrual cycle,
testosterone level 1. Appropriate
testosterone levels were recorded in a
journal which were then used in the final
data.
To measure physical arousal the
participant documented it in a journal
everyday on an arousal scale from 0-5, with
0 being not aroused at all during the day and
5 being aroused all day (see Appendix B).
This arousal scale was based off someone
who is awake for a period of 15 hours a day,
the amount of physical arousal does not
include hours during sexual activity. The
journal documentations were done
immediately before going to sleep at the
same time every evening so that physical
arousal could be used in the final data.
Amygdala activity was scored using
a measurement of heart rate. Heart rate,
measured in BPMs, was taken and recorded
in a journal first thing in the morning upon
waking up to provide a baseline. Every day a
YouTube clip was found with a jump scare
located in it. Heart rate, measured in BPMs,
was taken again immediately after jump
scare and recorded in the same journal to
track amygdala activity. The two heart rate
measurements were subtracted from each
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other and the difference of the two was used
in the final data.
Sexual activity was kept track of
using a journal. The participant kept track of
sexual contact including intercourse, oral
stimulation, as well as masturbation. The
person who initiated the sexual contact was
noted as ‘participant’ or ‘other’. Each
contact initiated by the participant was
counted as 2 (initiated and participated in
sexual activity) and each contact not
initiated by the participant as 1 (participated
in sexual activity). If the participant
attempted to initiate sexual activity and their
partner refused, a mark of 1 was also added
(attempted to initiate sexual contact). A total
for the end of each day was noted and used
in the final data.
To assess the strength and statistical
significance of associations between
variables predicted by our three hypotheses,
I performed Pearson product moment
correlations of their predictor variables
(testosterone, physical arousal, and
amygdala activity) with their outcome
variable (sexual activity). For testing
Hypothesis #1, I correlated testosterone
level, using the menstrual cycle, during the
day with the amount of sexual activity
during the day. For testing Hypothesis #2, I
correlated the participants physical arousal,
using an arousal scale of 0-5, during the day
with the amount of sexual activity during the
day. For testing Hypothesis #3, I correlated
the amygdala activity, using a difference of
heart rate in BPM, for each day with the
amount of sexual activity during the day. A
correlation coefficient was considered
statistically significant if the probability of
its random occurrence (p) was < .05 (i.e.,
less than 5% of the time expected by chance
alone).
2.2.2 Experimental Study Methods

Based on the strength of the correlation
between physical arousal and sexual activity
found in our correlational study, I then chose
to conduct an experimental study to test for
a causal relationship between these two
variables from Hypothesis #2.
I manipulated the independent variable,
physical arousal, over a two-week period by
randomly assigning participant each day to
either a high physical arousal day condition
or a low physical arousal condition. This
experiment was unable to use a double-blind
procedure. Experimental days involved
watching one pornographic video between
2-5 minutes long, in the morning to increase
physical arousal over the whole day. On
control days no pornographic video was
viewed. Sexual activity was kept track as
previously described in the correlational
study. This behavioural measurement helped
keep the study as objectives possible.
The experiment was done in an A/B
scenario. ‘A’ was the experimental days and
‘B’ was the control days. The experimental
and control days alternated every day.
To assess the statistical significance of
differences seen in sexual activity on high
physical arousal experimental days vs. low
physical arousal control days, t-tests were
performed. An average difference between
conditions was considered statistically
significant if, using a two-tailed distribution
(i.e., allowing this difference to be positive
or negative), the probability of its random
occurrence (p) was < .05 (i.e., less than 5%
of the time expected by chance alone).
3. Results
3.1 Correlational Study Results
Table 1 shows significant correlation
between all 3 predictor variables,
testosterone level, physical arousal and
amygdala activity, with the outcome
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variable, sexual activity. Testosterone level
was significantly correlated with sexual
activity (r = 0.56, p = 0.034936; see Figure
1). Physical arousal was significantly
correlated with sexual activity (r = 0.83 , p =
8.39E-05; see Figure 2). Amygdala activity
was significantly correlated with sexual
activity (r = 0.56, p = 0.035518; see Figure
3). The strongest correlation was found
between physical arousal and sexual
activity.
3.2 Experimental Study Results
No significant difference was found
between the high physical arousal condition
(pornographic video) and low physical
arousal condition (no pornographic video) as
shown in Table 2 (p = 0.54; see Figure 4).
4. Discussion
4.1 Summary of Results
For this project I hypothesised that sexual
activity would be positively correlated with
testosterone level (Hypothesis #1), physical
arousal (Hypothesis #2) and amygdala
activity (Hypothesis #3). The data from all
three correlational studies, testosterone
level, physical activity and amygdala
activity (Hypothesis #1,#2, and #3)
supported a significant positive correlation
with sexual activity. Unfortunately, the
results of the experimental study did not
support a causal role of physical arousal and
sexual activity.
4.2 Relation of Results to Past Research
The significant positive correlation
between testosterone level and sexual
activity was inline with research done
previously. Van Goozen, et al. (1997) found
that female sexuality is positively correlated

with higher levels of testosterone during
their menstrual cycle. Unfortunately, I was
not able to use the same number of women
in this research project or test as many
hormones with blood draws as Van Goozen,
et al. (1997). Despite this, the conclusions
remain similar suggesting a strong
relationship between testosterone levels and
sexual activity.
Previous research aligned with my
hypothesis of physical arousal positively
correlates with sexual activity. Ariely &
Loewenstein (2006) found that physical
arousal was correlated with engagement in
sexual activity among college men.
Although the participant in this study was a
woman a significant positive correlation was
still found. This suggests a strong
relationship between physical arousal and
sexual activity. However, after preforming
an experimental study I was unable to find a
significant causal relationship between
physical arousal and sexual activity.
Limitations for this experimental study
included not being able to perform a doubleblind procedure, only having one participant,
and being in school full time therefore not
having the time or energy to engage in
sexual activity even if there was a desire.
The previous study done by Ariely &
Loewenstein (2006) was an experimental
study but focused only on men, therefore a
similar study done on women could see
drastically different results.
My correlational study again aligned
with previous research suggesting a positive
correlational relationship between amygdala
activity and sexual activity. Savic &
Lindström (2008) had much more advanced
screening techniques for the brain and was
able to assess brains of people with different
sexualities. I was only able to assess my own
brain, without the advanced technology that
was available to Savic & Lindström (2008),
but still managed to find a positive
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correlation using the less advanced
technique of a heartbeat. The fact that I was
still able to collect data that ended in a
positive correlation between amygdala
activity and sexual activity suggests that
there is a strong relationship between these
two variables.
4.3 Implications of Results
Possible practical applications of the
current findings are the ability to feel less
ashamed about our sexuality because it is a
natural process that is influenced by many
different parts of our body. Odd’s suggest
that the time a female is the most sexually
active is when her testosterone level is
highest around the time of ovulation, which
means if you are trying to get pregnant your
body is trying to help you know when it is
the best time to engage in sexual activity.
The original studies were conducted
to learn as much as possible about the
different influences of human sexuality. The
findings, while not causal, still supported a
correlational relationship between
testosterone level, physical arousal and
amygdala activity with sexual activity. The
true cause of human sexuality still remains
to be discovered.

References
Ariely, D., & Loewenstein, G. (2006). The
heat of the moment: The effect of sexual

arousal on sexual decision making.
Journal of Behavioral Decision Making,
19(2), 87-98.
https://doi.org/10.1002/bdm.501
https://onlinelibrary.wiley.com/doi/epdf/1
0.1002/bdm.501
Reinisch, J. M., Mortensen, E. L., &
Sanders, S. A. (2017). Prenatal exposure
to progesterone affects sexual orientation
in humans. Archives of Sexual Behavior,
46(5), 1239–1249. https://doiorg.libsecure.camosun.bc.ca:2443/10.100
7/s10508-016-0923-z
Sanders, A. R., Martin, E. R., Beecham, G.
W., Guo, S., Dawood, K., Rieger, G., &
Duan, J. (2015). Genome-wide scan
demonstrates significant linkage for male
sexual orientation. Psychological
medicine, 45(7), 1379-1388.
https://doi.org/10.1017/S0033291714002
451
Savic, I., & Lindström, P. (2008). PET and
MRI show differences in cerebral
asymmetry and functional connectivity
between homo-and heterosexual subjects.
Proceedings of the National Academy of
Sciences, 105(27), 9403-9408.
https://doi.org/10.1073/pnas.0801566105
Van Goozen, S. H. M., Wiegant, V. M.,
Endert, E., Helmond, F. A., & Van de
Poll, N. E. (1997).
Psychoendocrinological assessment of
the menstrual cycle: The relationship
between hormones, sexuality, and mood.
Archives of Sexual Behavior, 26(4), 359–
382. https://doiorg.libsecure.camosun.bc.ca:2443/10.102
3/A:1024587217927

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Table 1
Correlation coefficient (r) values, with number of daily trials (n) per correlation in brackets.
Variables correlated
Testosterone level & Sexual activity

r(n)
0.56(14)*

Physical Arousal & Sexual activity

0.83(14)*

Amygdala Activity & Sexual activity

0.56(14)*

* p < .05.

Table 2
Descriptive statistics on sexual activity for a high physical arousal condition and a low physical
arousal condition.
Condition
High Physical Arousal
(Pornographic Video)

Statistic
Mean
S.D.
n

Sexual activity
0.86
0.90
7

Low Physical Arousal
(No Pornographic Video)

Mean
0.57
S.D.
0.79
n
7
Sexual Activity was measured on a 0-10 Scale, where 0=No Sexual Activity and 10=10 Sexual
Activities

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Figure 1

Sexual Activity (0-10 Scale, 0=No Sexual
Activity, 10=10 Sexual Activities)

Scatterplot of testosterone level and sexual activity.
4.5
4
3.5
3
2.5
2
1.5
1

0.5
0
0

2
4
6
8
10
Testosterone Level (1-14 Scale, 1=First Day Of Cycle, 14=Ovulation Day)

Figure 2

Sexual Activity (0-10 Scale, 0=No Sexual
Activity, 10=10 Sexual Activities)

Scatterplot of physical arousal and sexual activity.
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
0

0.5
1
1.5
2
2.5
3
Phsycial Arousal (Physical Arousal Through the Day 0-5 Scale, 0=No
Physical Arousal, 5=Arousal All Day)

3.5

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Figure 3

Sexual Activity (0-10 Scale, 0=No Sexual
Activity, 10=10 Sexual Activities)

Scatterplot of amygdala activity and sexual activity.
4.5
4

3.5
3
2.5
2
1.5

1
0.5
0
0

5
10
15
20
Amygdala Activity (Difference in Heart Rate (BPM) Before vs After a
Scary Video)

25

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Figure 4
Bar graph of average sexual activity across high physical arousal condition and low physical
arousal condition, with error bars showing ± 95% confidence levels.

Sexual Activity (0-10 Scale, 0=No Sexual
Activity, 10=10 Sexual Activities)

Raw Data
2.5
2
1.5
1
0.5
0
-0.5

High Physical Arousal (Pornographic
Low Physical Arousal (No
Video)
Pornographic Video)
Physcial Arousal

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Appendix A
Menstrual Calendar
October 2020
Sunday

Monday

Nov 20

Tuesday

Nov 21

Wednesday

Nov 22

Thursday

Nov 23

Friday

Nov 24

Saturday

Nov 25

Nov 26
Period Day 1
Testosterone
1

Nov 27

Nov 28

Nov 29

Nov 30

1

2

3

Testosterone

Testosterone

Testosterone

Testosterone

Testosterone

Testosterone

Testosterone

2

3

4

5

6

7

8

4

5

6

7

8

9

10

Testosterone

Testosterone

Testosterone

Testosterone

Testosterone

Approximate

Testosterone

9

10

11

12

13

Ovulation

13

Day
Testosterone
14
11

12

13

14

15

16

17

Testosterone

Testosterone

Testosterone

Testosterone

Testosterone

Testosterone

Testosterone

12

11

10

9

8

7

6

18

19

20

21

22

23

24

Testosterone

Testosterone

Testosterone

Testosterone

Testosterone

Approximate

Testosterone

5

4

3

2

1

Period Day 1

2

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25

26

27

28

29

30

31

Testosterone

Testosterone

Testosterone

Testosterone

Testosterone

Testosterone

Testosterone

3

4

5

6

7

8

9

Based on “Clue” the period tracking app. Period days are filled with red. Fertile days are filled
with pink. Ovulation day is filled with yellow. Approximate next period is filled with rose.

Appendix B
Arousal Scale

0

1

2

3

4

5

0: No arousal during the course of the day (0 hours a day)
1: Little arousal during the course of the day (1-3 hours a day)
2: Some arousal during the course of the day (4-6 hours a day)
3: Aroused quite a few times during the course of the day (7-9 hours a day)
4: Arousal a lot of the time during the course of the day (10-12 hours a day)
5: Aroused most of the course of the day (13-15 hours a day)

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