1. Its just a
little blood
Lyle, H. F., Smith, E. A., & Sullivan, R. J. (2009).
Blood donations as costly signals of donor quality.
Journal of Evolutionary Psychology, 7(4),
263-286.
Why do we give blood in the first
place?
• Blood donation is pure altruism, there is NO
direct benefit to the donor
• This may explain shortages in blood
supply
• The Costly Signalling Theory suggests
donors are honestly signalling cooperative
intent and good genetic health
!
• AIM:to see if -
• donors are seen as generous
(supported) and healthy (supported)
• the perceived costs reduce likelihood
of donating (supported)
• and differ between donors & non
donors (supported)
!
• so we can encourage others
MEthod:
• 346 college students
completed an online survey
assessing (using likert scales):
• Cost of donating (Anxiety, pain,
negative health consequences, inconvenience)
• Perceived generosity of
donors vs blood demand
• perceived health of
donors
• Likelihood to make a
future donation
• Compared donor and non
donor groups
Results:
• a s i g n i f i c a n t n e g at i v e
relationship was found between
likelihood of future donation
and both potential negative
health consequences and anxiety
• D o n o r s w e r e f o u n d t o b e
considerably less concerned
a b ou t a n t ic i pat e d pa i n a n d
anxiety than non donors
• Blood donors were perceived by
both groups to be healthy and
disease free, but being physically
fit was deemed unnecessary
Discussion:
• A costly signal only
s e r v e s a p o s i t i v e
f u n c t i o n i f t h e
receiver understands
its worth
• The results show that
people understood the
need for blood, and so
consider donation a
generous & altruistic
act
• R e du c e d a n x i e t y i n
donors may make them
more attractive as an
ally or potential mate
as they appear to cope
better under pressure
• f u t u r e
r e s e a r c h
should test
w e t h e r
generosity of
d o n o r s
generalises to
other circumstances
Luke Costley
White