This experiment is part of the Sleep Challenge Grant. Browse more projects

Men, women, sex and sleep behaviour

Raised of $4,025 Goal
Ended on 7/15/16
Campaign Ended
  • $297
  • 8%
  • Finished
    on 7/15/16

About This Project

“Evening men”, who go to bed and get up late, have more sexual partners and more extra-pair matings than “morning men”, who get up early and go to bed early. Evening people are often nicknamed "Owls", and morning people "Larks".

This is related to testosterone: evening types have a higher testosterone level. Does evening type signal good genes? To test this, we want to assess immunocompetence and sperm quality as surrogates of good genes and compare evening with morning types.

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What is the context of this research?

Men with high testosterone levels and a “later” sleep behavior have a higher mating success. We want to know if this is is this related to the good genes hypothesis.

Studies show relations between morningness and higher business ( and school success but also between eveningness and higher mating success (our previous study). But why is mating success higher in evening types? Is there a biological explanation? Is it related to evolution. Is it the "good genes"?

We want to assess surrogates of good genes and compare them between evening types and morning types. This will be set in relation with salivary testosterone as well as sleep behavior and a battery of questionnaires about sexual behavior.

What is the significance of this project?

These questions have never been tested before. We apply evolutionary theory (the good genes hypothesis) to human behavior. We try to emulate animal studies that showed relationships between testosterone, mating success and "good genes", but transfer the question to humans.

Three of our previous studies showed that this eveningness behavior is indeed related to a different sexual behavior.

When evening people have a higher mating success, this should be related to biological findings. So, the good genes might be an explanation. How can we test this? Good genes cannot be easily measured, so we need surrogates. Therefore, we measure sperm quality, testosterone and a marker of health.

We test correlations between eveningness and these measures.

What are the goals of the project?

We hope to get insight into the human mating system with a focus on sleep behavior (in the sense of morningness-eveningness) and to assess, if the higher mating success of evening types is related to their quality (health, sperm quality).

This work is of great interest. If we can show this relationship, we get new insights. Usually, morning people "rule the world" (, but the "winners" in evolutionary terms might be the evening people with a higher mating success.

This would show that different types (morning versus evening) have different profiles that are related to success in its widest sense.


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The testosterone is measured in saliva. The testosterone level can be related to sexual behavior and to evening orientation. So evening types have higher testosterone, which could explain the result. Measuring in saliva is easier than in the blood for our participants. This helps us to find men that are interested in the work.

To test the good genes hypothesis, we assess immunocompetence in saliva and make a spermatogram, to see, if evening types have a better health and more viable sperm. Sperm quality is a measure of "fitness" and of good genes. So we check the sperm to see if the evening men have more volume or higher quality (motiliy).

Immunocompetence shows how good the immune system of a person is. For this, we need assays of some immune markers.

The research assistant is needed to inform the people of our research, to get samples (saliva etc.) from the participants. The assistant should be a student because he will be able to communicate better with our population.

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Perfect project. The proposal is very actual and research findings will be of interest of major journals in this field. Therefore, it sounds to be more than promising, good luck with this!
The team of Prof. Randler is one of the world's leading in research about relations between morningness-eveningness with biological and psychological aspects of individuals. This research aims to explore a topic of undoubted theoretical and applied interest. The results will have an impact both through scientific publications and media.
Dr. Randler has realized relevant findings in chronopsychology and chronobiology topics during the last decades. This new research integrate biology and psychology disciplines using multivariate methodology. The results will shed light on the interesting relationship between sex and individual differences in sleep behavior.
I am really excited for this project. Christoph Randler has proven to be most knowledgeable in the field of morningness-eveningness and biological correlates. His previous studies include research on several biological variables that may influence chronotype, for example, testosterone, light at night, food intake, sex, latitude, season of birth, sleep length, cortisol, and physical activity.
This is a very exciting project which may shed light on evolutionary processes resulting in the fact that some of us prefer later hours than others. The budged of the project is very reasonable and previous works of prof. Randler and his coworkers along with his experience in the field guarantee the success in accomplishing this research.
Dr. Randler and I met at a conference in St. Louis after an excellent presentation that he gave on the major differences between morning people and evening people. We have since been in collaboration on a project regarding the validation of an animal rights scale cross-culturally. He is an excellent research and a great colleague, and I have no doubt that he will meet the same standards with this project.

Meet the Team

Christoph Randler
Christoph Randler
Prof. Dr.


University of Tuebingen
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Arash Rahafar
Arash Rahafar


University of Tübingen
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Corina Faßl
Corina Faßl

Christoph Randler

born 1969

PhD in 2003

2005 junior professor (assistant) Univ Educ Ludwigsburg

2006-2007 W2 professor Univ Leipzig

2007-2015 W 3 professor (full) Univ Educ Heidelberg

2016-now W 3 professor Univ Tuebingen

After having done "mainstream" research for many years, I now want to do some work that is not "traditionally" funded by usual organizations, so I am happy to be part of the Experiment. You can help me doing my work, exploring the cutting edge science - in between fields of biology and psychology. I like switching between the fields - I have done work on "real" birds, also on biology education (with the hope to improve school teaching). Now I am interested how our "neglected third" of our life - the sleep and sleep behavior is related to personality, society and health.

Arash Rahafar

I was born in 1988 in Tehran. My bachelor study was in clinical psychology, my master in psychometrics, and since 2014 I've started my PhD at University of Education Heidelberg at first, and then continued at University of Tübingen. I do my research mainly in the domain of circadian rhythms however I'm also occupied with interpersonal relationships topics and social psychology studies.

Corina Faßl

born 1990

2011-2014 BSc. (psychology)

the health and life sciences Univ

2014-2016 MSc. (psychology)

the health and life sciences Univ

PhD since 2016 Univ Tuebingen

After I have already dealt with chronobiology in my bachelor- and master thesis, I’m happy to get the chance to deepen this area of research (sleep behavior, in sense of morningness- eveningness). The combination of chronobiology with personality and sexual behavior will be a promising research.

Additional Information

One of the challenges of the project will be to find participants that agree to deliver data and material - we hope to fix this with the help of male student researchers.

Project Backers

  • 8Backers
  • 8%Funded
  • $297Total Donations
  • $37.13Average Donation
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