In domestic chicks and other species of birds exhibiting USWS, one eye remained open contra-lateral to the "awake" hemisphere. The closed eye was shown to be contra-lateral to the hemisphere engaging in slow-wave sleep. Learning tasks, such as those including predator recognition, demonstrated the open eye could be preferential.[6] This has also been shown to be the favored behavior of belugas, although inconsistencies have arisen directly relating the sleeping hemisphere and open eye.[7] Keeping one eye open aids birds in engaging in USWS while mid-flight as well helping them observe predators in their vicinity.[8]