“Darwinian continuity need not demand greater mental powers in nonhuman animals than is currently evident” (target article, sect. 6, para. 10). With this closing sentence, Suddendorf & Corballis (S&C) seem to dismiss the possibility that nonhuman species may mentally travel in time or possess any of its components. However, their approach to mental time travel (MTT), distinguishing different cognitive components, that is, the “play” (or theater) metaphor, actually allows for a Darwinian continuity without MTT in animals. Moreover, the conditions for MTT in animals are laid out, so the capacity of MTT itself can be investigated. Our research on future-oriented behaviour in chimpanzees (Dufour & Sterck, submitted; Dufour et al. Reference Dufour, Pelé, Sterck and Thierry2007), and recent studies on other apes (Mulcahy & Call Reference Mulcahy and Call2006) and birds (Raby et al. Reference Raby, Alexis, Dickinson and Clayton2007), indicate that these animals can plan for future needs and have some of the mental capacities required for MTT.

New research indicates that flexible future-oriented behaviour in animals exists. Animals show future-oriented behaviour when they act in the present on the basis of an anticipated future need in contrast to a current one. The results of the sole study on apes showing such planning behaviour in tool use tasks (Mulcahy & Call Reference Mulcahy and Call2006) are not considered convincing by S&C. They argue that the apes “only” needed to learn to always return with the same tool. Moreover, the set-up allowed for tool collection based on a current need since the apparatus was visible. Our results on chimpanzees, however, counter this interpretation. We replicated the Mulcahy and Call study with additional methodological controls: Chimpanzees had to collect the appropriate tools and bring them back while the apparatus and experimenter remained out of sight. Some individuals transported the appropriate tools (Dufour & Sterck, submitted). Moreover, the animals had not previously succeeded in a planning-like task that required them bring in a tool, and also never had to bring the tool during training, so a previously learned rule cannot account for their behaviour. Therefore, our study indicates that chimpanzees can collect tools without direct indications of future use (Dufour & Sterck, submitted).

Similarly, scrub jays can store their breakfast in the evening at a location where they occasionally are forced to spend the night, but are never provided with breakfast, suggesting future-oriented behaviour not driven by current need (Raby et al. Reference Raby, Alexis, Dickinson and Clayton2007). Although more controls are needed, these results are first indications that animals, too, may possess capacities related to MTT. In addition, planning for the future and recollection of past experiences are probably linked (e.g., Suddendorf Reference Suddendorf2006). An increasing body of research concerns recollection of past events, or episodic-like memory, in animals, reviewed by S&C (sect. 3.1). Although they conclude that animals lack MTT, their review shows that rodents, monkeys, great apes, and scrub jays can associate two or more elements (what, where, when, who) from a past experience and combine them to direct current behaviour. Altogether, these results indicate that not all animals are strictly bound to the present.

S&C list in the “play” metaphor a challenging range of mental capacities that are components of MTT. From the capacities mentioned, the ”broadcaster” is probably not required for MTT, although it may enhance joint action. In addition, not all capacities may be required to the degree proposed by S&C.

S&C suggest that animals must possess some “appreciation of the time dimension itself” (sect. 4.4), that is, “the set.” Most tests of time understanding in animals show the limited capacities of monkeys, rats, and pigeons in choosing a delayed large reward over a directly available small one. However, we showed that chimpanzees may appreciate exactly this time dimension. In a ”waiting to exchange task,” we determined the capacity of capuchin monkeys and apes to wait (Dufour et al. Reference Dufour, Pelé, Sterck and Thierry2007; Ramseyer et al. Reference Ramseyer, Pelé, Dufour, Chauvin and Thierry2006). Animals were given an initial item of a desired food (a cookie) that they had to keep for some time and exchange later for a larger-sized cookie. While capuchins did not wait for more than 20 to 40 seconds, chimpanzees kept the initial cookie for at least 8 minutes. Interestingly, chimpanzees gave up waiting earlier than predicted by their general ability to wait. This suggests some appreciation of the duration of the delay, and a flexible capacity of weighing different options based on time to and size of what is to come relative to what is currently available. Chimpanzees appreciate the time dimension for a time period exceeding that of other tested animals, and their performance resembles that of children (Mischel et al. Reference Mischel, Shoda and Rodriguez1989).

The results of the “waiting to exchange task” are also relevant for the “executive producer” capacity. They indicate that chimpanzees can “[inhibit] a simple response in order to increase” their “total future reward” (sect. 4.6). In addition, chimpanzees had voluntary control over this inhibition, since, with the longer waiting times, they either decided to control themselves or chose not to.

In “the actors” part, the ability to project self into the past or the future, MTT requires self-awareness. S&C imply that theory of mind (ToM) is a prerequisite to MTT. However, ToM is also considered an advanced cognitive capacity often attributed to humans only. Similar to what S&C propose, ToM has also been proposed to require a number of components, among them the capacity to appreciate the future (Barrett et al. Reference Barrett, Henzi and Dunbar2003, p. 496). This suggests that one is not part of the other, since they are two different capacities, but that both MTT and ToM depend partly on the same components.

In conclusion, our results on future-oriented behaviour in chimpanzees indicate that they possibly show future planning and have some of the mental capacities required for MTT. The search will be on for the others. As S&C also acknowledge, before accepting the conclusion that “Darwinian continuity need not demand greater mental powers in nonhuman animals than is currently evident,” we have to test animals before dismissing their MTT-related capacities.