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 about anticipated pain and 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 rv 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

• Reduced anxiety in 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