% implementation of "parallel lines task" described by
% Herrnstein and Prelec (1991)

n=8; maxiter=1000; 
choices=zeros(1,maxiter); buffer=zeros(1,n);
buffer(1:2:end)=1; buffer(2:2:end)=2;
for iter=1:maxiter
  k=menu('Choose a color','Red','Green');
  freq=sum(buffer==1)/n;
  delay=2*k*(1-freq)+freq*(2*k+4);
  choices(iter)=k;
  buffer=[buffer(2:end) k];
  pause(delay)
end