Within the broad framework of evolutionary theory it is possible to develop a
sustainable foundation for social dominance-hormone relationships in women.
However, whilst providing an important contribution towards understanding the role of
biology in social dominance, hormone-competition interactions have received
considerably less attention in females than in males. Consequently, the thesis explores
the relationship between salivary testosterone (T), Cortisol (F), and non-physical
competition in women.
petition in women.
In order to address widely acknowledged difficulties with determining levels of
female T, particularly the biologically active 'free' fraction as measured in saliva, a
highly sensitive 'in-house' enzyme-linked immunosorbant assay (ELISA) was
optimised and validated. Assay sensitivity was 0.5pg/mL; intra and inter-assay
coefficients were 2.1% and 6.7% respectively; recovery ranges were between 96-105%;
cross reactivity with related compounds was minimal - i.e. androstendione <8%. A
modest correlation with a commercially available T assay kit is discussed in relation to
the limitations inherent in direct enzyme assays. The ability to measure salivary free T
at levels below those easily available to users of commercial kits is fundamental to the
work in this thesis.
In the absence of reliable information on the daily profile of female free T, biobehavioural studies have tended to formulate salivary sampling strategies taken directly
from research involving male subjects. However, this approach may be inappropriate.
Accordingly, by determining a comprehensive picture of the circadian activity of
salivary T in 36 healthy female subjects, it was possible to demonstrate that T follows a
circadian rhythm, the relative levels of which differ over two non-consecutive days.
Moreover, throughout the course of the day T levels were highly variable, with episodic
fluctuation of individual data points exceeding 83% of 9am levels. These findings
highlight the necessity of collecting multiple samples in bio-behavioural research
involving T and women.
Incorporating methodological refinements in both the measurement of T and
sampling protocol, an experimental study sought to examine the dynamic relationship
between T, F, and non-physical dyadic competition. Twenty-two females (ages 19-24
years) competed in a knockout tournament involving the wood-block game 'Jenga'.
They collected comprehensive salivary samples for baseline, pre- and post-competition
phases. Subjects additionally reported mood states and answered questions concerning
their participation in the competition. Whilst the comprehensive hormonal data resist
easy interpretation, compared against baseline levels, pre-comp T and F appeared un¬
responsive in anticipation of competition. However, at 3 hrs post-competition, T levels
rose 35% in winners and fell 4% in losers. F levels, conversely, fell in both losers and
winners, although in winners this drop was much more pronounced. These results
suggest that, similar to males, women experience a dynamic endocrine response
following competition. However, the extent to which T is implicated in female social
dominance is likely to be extremely small. The findings further illustrate how choice of
competitive task and hormonal sampling regimens used in previous studies may, to a
large extent, account for the equivocal findings in the literature. Additional research is
required to ascertain ifthis pattern of endocrine response holds under a wider variety of
competitive situations and also to explore more fully the psychological processes
mediating hormonal responses to competition.