stimuli method
Implementation
String stimuli() {
String ret = '';
for (var i = 0; i < 5; i++) {
if (i == 2) {
ret += direction;
} else if (congruent) {
ret += direction;
} else {
if (direction == '→') {
ret += '←';
} else {
ret += '→';
}
}
}
return ret;
}