Cognitive illusions are:(there are 4 types of cognitive illusions)
Cognitive illusions are assumed to be an interaction based on assumptions about the world, which lead to unconscious inferences an idea first suggested in the 19th century by Herman Helmholtz.
(http://www.unisaustralia.com/university-quizzes-problems-brain-teasers-and-experiments/psychological-illusions-and-puzzles/cognitive-psychological-optical-illusions/)
(http://www.unisaustralia.com/university-quizzes-problems-brain-teasers-and-experiments/psychological-illusions-and-puzzles/cognitive-psychological-optical-illusions/)