Testosterone increases the urge to sing yet decreases the quality of birdsong, according to research at John Hopkins University.
Increasing testosterone levels in the brain demonstrated an increase in the desire to sing and volume of song, yet reduced the size of a separate area in the brain that regulates song quality.
The findings on testosterone and its affect on the brain are hoped to further understanding of how the hormone testosterone acts in the human brain to regulate speech, and how anabolic steroids (prescription drugs used to increase testosterone levels) affect human behaviour.
The ability of a male canary to sing a pitch-perfect song is essential in wooing a female canary. The quality and frequency of song changes through the seasons and it is the hormone testosterone which plays a major role in changing song behaviour.
To determine how testosterone influences birdsong, researchers divided 20 canaries into two groups to receive a hormone implant:
- group one received testosterone in the medial preoptic nucleus, or POM (an area in the hypothalamus responsible for sexual motivation in animals and humans)
- group two received testosterone that acted throughout the whole of the brain
- group three was a control group and received no hormone treatment at all
Both of the groups that received testosterone treatment (group one and two) sang. However researchers noticed that in some cases in group two the canaries’ songs were sung poorly. The birds that only received testosterone to the POM area (group two) sang at high rates, but could not produce high quality song that is most attractive to females. Lead researcher, Dr. Alward, commented:
Our data suggests that testosterone needs to act in different areas of the brain to regulate the specific components of this complex social phenomenon. It appears that, like in so many other species, testosterone in the POM can regulate an animal’s motivation, in this case, the motivation to sing.
However, singing and courting a female is more than just motivation. There is the quality of the song that is required to successfully attract a mate and then the process of attending to the female, or singing to her, when she is there which requires the coordination of multiple brain regions.”
The canaries that received testosterone throughout the brain displayed high-quality typical canary vocalization behaviour – consistent with the idea that testosterone acts on several different brain areas to regulate how much as well as how well the birds can sing.
The researchers say these results have broad implications for research concerning how steroid use in humans affects sexual behaviours and how hormones regulate the difference components of speech in humans. Dr Alward added:
The hormones in these birds are identical to those in humans and they can regulate brain changes in a similar manner.”
John Hopkins University Press Release: Testosterone in male songbirds may enhance desire to sing but not song quality
PNAS: Differential effects of global versus local testosterone on singing behaviour and its underlying neural substrate
Image: thanks to Flickr