The cages consisted of interconnected indoor and outdoor enclosures. Cognition, Tactical deception, Sneaky mating, Hiding, Macaque, Old world monkey Introduction Social complexity is considered an important selective force driving animal intelligence, as proposed in the social intelligence hypothesis Jolly ; Humphrey ; Byrne and Whiten ; Dunbar Gygax ; Kummer et al. All individuals had several potential non-kin i. Tactical deception level 2. Non-alpha males and females can copulate sneakily to counter the monopolization of females by dominant males hamadryas baboon, Papio hamadryas: Strategies 2—4 may be learned by operant conditioning. However, water was available ad libitum in the outdoor enclosure. In any event, in both species non-alpha males and females have incentives to hide sexual behaviour. TD in corvids Bugnyar and Heinrich and apes is found up to level 2 Hare et al. Abstract Although tactical deception TD may be employed to hide sexual behaviour, there is as yet no firm evidence for it. TD level 1 may be achieved by learning a specific behaviour that often results in deception with a benefit for the deceiver i. Moreover, it is not clear what property of the screens elicited this preference: The fourth strategy will be more effective, but requires learning a slightly more complex rule than the first three strategies. Ruiz de Elvira and Herndon ; Overduin - de Vries et al. If we were to find this, this would warrant a follow-up study to discriminate between strategies 4, 5 and 6. This article has been cited by other articles in PMC.