From Halopedia, the Halo wiki
The Expectation Effect is a philosophical theory presented by Sangheili cosmo-philosophers, rooted in the premise that consciousness itself is a quantum phenomenon. The Expectation Effect assets that it is impossible to percieve an object without knowing either its location or its vector, and that by knowing either of these things it becomes impossible to not percieve the object; an observer percieves what they expect to see and does not percieve that which they do not expect to see.
The Expectation Effect is a core principle of the application of Precursor nanotechnology like that found inside the Inner Sanctum on Netherop. When the Sanctum's Hide armour created by the nanodust granted Nizat 'Kvarosee and his followers, none of the assaulting party led by Thel 'Vadam was able to see the defenders until Meduz 'Ra'ashai pointed out the presence of the blood trails from their injuries; after that point, 'Vadam expected to see the Defenders, and was thus able to see them. Later inside the Divine Hand chamber, the nanodust similarly reacted to Thel's musings on the United Nations Space Command stealth cruiser UNSC Hidden Point, and showed him the ship's location without him ever asking for it.
List of appearances
- Halo: Outcasts (First mentioned)
- Halo: Outcasts, chapter 20