An area of longstanding interest in comparative cognition is time perception, i.e., the ability to detect the passage of time. In general, time perception has to do with the question of whether other animals live entirely in the present or can anticipate a future.

Basic time perception is considered by many scientists to be requisite for the more sophisticated process of mental time travel—the conscious ability to mentally represent the past and plan for the future. The ability to travel backwards in time and recollect specific past events is called episodic memory. It has been argued that episodic memory is tied to mental time travel (Dere et al. 2006). Arguably, therefore, when coupled with an episodic memory system, time perception becomes evidence for an autobiographical sense of self in the past, present, and future.

Perception of time intervals

Many animals have a sense of time duration, which helps them to know the time of day and predict when events will occur (Gallistel 1994; Richelle and Lejeune 1980). Domestic pigs (Sus scrofa domesticus) for instance, show a capacity for temporal response differentiation (Ferguson et al. 2009) and distinguishing between short versus long time intervals (Spinka et al. 1998). Furthermore, they are able to anticipate future negative or positive events (Imfeld-Mueller et al. 2011).

Chimpanzees (Pan troglodytes) and other great apes show sophisticated abilities in the time perception realm, as they are able to prepare themselves for future actions (e.g., tool use: Beran et al. 2004; Osvath and Osvath 2008) even as much as 14 h in advance (Mulcahy and Call 2006). They also demonstrate a capacity for episodic memory. They can remember highly specific contextual elements; that is, the what, where, and when of events when an hour or even two weeks have passed (Martin-Ordas et al. 2010, 2013). Bottlenose dolphins also show robust evidence of episodic memory in complex tasks requiring them to directly access memories of behaviors they have performed previously (Mercado et al. 1998).

At the simplest level, studies of time perception in birds have shown that a number of avian species, e.g., pigeons (Roberts et al. 1989) and black-capped chickadees (Parus atricapillus) (Brodbeck et al. 1998), are able to estimate short time intervals of up to 60 s. This has been demonstrated using operant conditioning techniques in which the pattern of peck responses indicates the bird’s ability to anticipate an upcoming food reward. However, these and other bird species have shown temporal abilities that go beyond these findings when given the opportunity. For instance, one study with pigeons showed they were capable of judging intervals of up to 8 min (Zeiler and Powell 1994). Western scrub jays (Aphelocoma californica) make provisions in advance for a future need, both by preferentially caching food in a place where they have learned that they will be hungry the next morning, and by differentially storing particular food items in a place in which that type of food will not be available the next morning (Raby et al. 2007).

In the only study directly testing time perception in chickens, five thirty-week old hens were able to predict, approximately, a 6-min interval when given a reliable predictive visual signal (Taylor et al. 2002). The hens were required to peck a computer-controlled touch screen that delivered a food reward upon the first peck after 6 min. The hens showed they were capable of estimating the time interval by showing a pattern of increased pecking frequency around the 6-min mark. As good as the chicken’s performance was, it should be noted that they were able to achieve this performance within a highly artificial setting. Almost certainly, a more naturalistic setting would allow the chickens’ temporal abilities to be more easily demonstrated, as all animals, including birds, depend upon the appropriate environmental context for the full expression of their behavior.

In another study which tapped into time perception through an anticipatory emotional response, laying hens were taught to discriminate three sounds which signaled either a positive outcome (food reward), a negative outcome (a squirt from a water gun) or a neutral outcome (nothing) after a 15-s delay. The hens showed differential emotional responses to the different sounds suggesting that they were able to anticipate a future outcome (Zimmerman et al. 2011). More details about the birds’ emotional responses can be found in the section on Emotions below.

Episodic memory

Studies of episodic memory provide a window into the question of whether other animals remember personal experiences, i.e., possess episodic memory. Episodic memory, a component of declarative memory, is tied to whether an individual experiences life autobiographically (autonoetic consciousness). Tulving (2005) defined episodic memory in terms of its subjective experience. Moreover, the demonstration of episodic memory in other animals has been argued to be probative of autonoetic conscious experience, as it relies upon distinctive personal memories (Dere et al. 2006; Eichenbaum et al. 2005; Martin-Ordas et al. 2013).

In addition to many mammals, including great apes (Martin-Ordas et al. 2013; Schwartz et al. 2005), a number of bird species demonstrate evidence for memory described as “episodic-like” (Clayton and Dickinson 1998). In a visual discrimination task which allowed for control over confounding variables, Zentall et al. (2001) found some evidence for episodic memory in White Carneaux pigeons. In this study, the pigeons were essentially asked the question: “Did you just peck or not?” and they remembered specific details which allowed them to “answer” this question with key pecks. In other studies, pigeons have demonstrated meta-knowledge about the behavior they just emitted, that is, knowledge about their own knowledge (Shimp 1982).

But in other studies, the evidence for metacognition is inconclusive (Iwasaki et al. 2013). Western scrub jays (Aphelocoma coerulescens) show evidence of episodic memory, i.e., the what, where, and when of food-caching episodes. Jays can remember when and where they cached a variety of foods that differ in the rate at which they decay, and retrieve those stored foods later in the appropriate order. They can update their memory of the contents of a cache depending upon whether they have previously visited the site. Furthermore, they can also remember where other birds cache their food, showing that they encode rich mental representations of caching events (Clayton et al. 2001, for a comprehensive review of these studies). Although there has been some debate about whether these findings represent episodic memory or other forms of associative learning (Suddendorf and Corballis 2007), these criticisms have been disputed (Raby et al. 2007). Clearly, some very interesting complex cognitive processes are coming into play in these food-caching behaviors.

In a more direct test of metacognition in scrub jays, the birds were required to allocate a proportion of time looking into two peepholes in order to see food being hidden in either of two compartments, one where observing the hiding location was necessary to later relocate the food, and another where food could easily be found without watching. The jays first separately experienced the consequences of possessing information in each compartment and subsequently, once given a choice, made more looks and spent more time looking into the compartment where information was necessary than into the compartment where it was unnecessary. Thus, the jays showed that they not only can differentiate sources of information according to their potential value but they can collect information needed to solve a future problem (Watanabe et al. 2013).

As mentioned above, the presence of episodic memory in chickens might be inferred from findings like the ones described above on time perception and anticipation, which probe capacities that are correlated with episodic memory. But there are other ways to more directly investigate the presence of episodic memory in chickens. Studies of memory using a matching-to-sample paradigm may reveal episodic-like memory components because they require the subject to “declare” the characteristics of a stimulus they have kept in memory. Hens can successfully complete these tasks, but the delays used are typically very short (on the order of seconds, see Foster et al. 1995). In studies of Stage 4 object permanence like those described above, episodic memory can be tested by imposing a delayed response procedure that requires maintaining a memory of a specific event over a longer period of time than just a few seconds. Chickens are able to remember the trajectory of a hidden ball for up to 180 s if they could see the ball moving and up to 1 min if the displacement of the ball was invisible to them (Vallortigara et al. 1998). In other words, they did as well as most primates (Wu et al. 1986) under similar conditions.

In other studies, five-day-old chicks were fed with two plates, each with a different kind of food. The food was devalued by pre-feeding with one of the food types, thus decreasing the novelty and incentive for that food type compared with the other. When tested later (on the order of a few minutes), the checks went to the location where they had previously found food (Cozzutti and Vallortigara, 2001). Similar results have been found for hens (Forkman 2000) showing that chicks and adult chickens are capable of remembering the “where” and “what” components of information about food.

Self-control

Self-control can be broadly defined as the ability to resist immediate gratification for a later benefit. It may be associated with planning for the future because foreplanning requires not only mental time travel, but the ability to inhibit or delay a response until later. However, the relationship between self-control and planning for the future is still in need of clarification in many studies.

Self-control may also be associated with the development of self-awareness (Genty et al. 2004) and autonomy—the ability to think about and choose future outcomes. Self-control is typically not reliably demonstrated in human children until they are at least 4 years of age (Mischel et al. 1989). Self-control is generally assessed in humans and other animals by determining whether they can delay obtaining a small reward for a larger reward later. Thus, these tests are prospective timing tasks requiring prediction of an outcome in the future based on experience in the past. Many mammals show self-control under these circumstances, including rats (Rattus norvegicus) (e.g., Chelonis et al. 1998; Flaherty and Checke 1982), and primates, such as lemurs (Eulemur fulvus and E. macaco) (Genty et al. 2004), rhesus monkeys (Macaca mulatta) (Beran et al. 2004), chimpanzees and orangutans (Pongo pygmaeus) (Beran 2002; Osvath and Osvath 2008).

A number of avian species demonstrate self-control in experimental situations, including pigeons (e.g., Logue et al. 1985; Mazur 2000), black-capped chickadees (Feeney et al. 2009, 2011), and, in a similar paradigm to that used with primates, the carrion crow (Corvus corone) and the common raven (Corvus corax) (Dufour et al. 2011).

Domestic chickens, too, show the capacity for self-control in an experimental setting. In a situation where they are given a choice between a 2-s delay followed by access to food for 3 s or a 6-s delay followed by access for 22 s (a veritable jackpot), hens held out for the larger reward, demonstrating rational discrimination between different future outcomes while employing self-control to optimize those outcomes (Abeyesinghe et al. 2005). Given the promising results of this study, more exploration of the cognitive basis of self-control in chickens is indicated.