setupDots.m

% This code reproduces the analyses in the paper
% Urai AE, Braun A, Donner THD (2016) Pupil-linked arousal is driven 
% by decision uncertainty and alters serial choice bias. 
% 
% Permission is hereby granted, free of charge, to any person obtaining a 
% copy of this software and associated documentation files (the "Software"), 
% to deal in the Software without restriction, including without limitation 
% the rights to use, copy, modify, merge, publish, distribute, sublicense, 
% and/or sell copies of the Software, and to permit persons to whom the 
% Software is furnished to do so, subject to the following conditions:
% 
% The above copyright notice and this permission notice shall be included 
% in all copies or substantial portions of the Software.
% If you use the Software for your own research, cite the paper.
% 
% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 
% OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
% AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
% FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
% DEALINGS IN THE SOFTWARE.
%
% Anne Urai, 2016
% anne.urai@gmail.com

function [dots, fix] = setupDots(window)

% DOTS CHARACTERISTICS
dots                   = struct; %preallocate
% parameters that stay constant
dots.radius            = deg2pix(window, 12); %keep constant
dots.innerspace        = deg2pix(window, 2);
dots.lifetime          = 4; % in frames
dots.nvar              = 3; %interleave two variants of the stimulus
dots.color             = [255 255 255]; % always 100% dot contrast

% determine the appearance of the dots - as in Siegel, 2007
dots.speed             = deg2pix(window, 11.5); % speed of the dots in degrees/second
dots.size              = deg2pix(window, 0.2); %size of each dot in degrees
dots.density           = 1.7; % dot density in dots per degree^2
dots.nDots             = round(dots.density*pi*pix2deg(window, dots.radius)^2); %number of dots in the circle, calculated from density (can also just be a fixed nr, eg. 500

% FIXATION
% this is the fixation descibed in Thaler et al. 2013
fix.dotsize         = deg2pix(window,0.2); % fixation dot
fix.circlesize      = deg2pix(window,0.6); % circle around fixation dot
fix.color           = [255 0 0];

end