Thomas Suddendorf

The evolution of foresight: What is mental time travel and is it unique to humans?

In a dynamic world, mechanisms allowing prediction of future situations can provide a selective advantage. We suggest that memory systems differ in the degree of flexibility they offer for anticipatory behavior and put forward a corresponding taxonomy of prospection. The adaptive advantage of any memory system can only lie in what it contributes for future survival. The most flexible is episodic memory, which we suggest is part of a more general faculty of mental time travel that allows us not only to go back in time, but also to foresee, plan, and shape virtually any specific future event. We review comparative studies and find that, in spite of increased research in the area, there is as yet no convincing evidence for mental time travel in nonhuman animals. We submit that mental time travel is not an encapsulated cognitive system, but instead comprises several subsidiary mechanisms. A theater metaphor serves as an analogy for the kind of mechanisms required for effective mental time travel. We propose that future research should consider these mechanisms in addition to direct evidence of future-directed action. We maintain that the emergence of mental time travel in evolution was a crucial step towards our current success.

Mental time travel in animals

Are humans alone in their ability to reminisce about the past and imagine the future? Recent evidence suggests that food-storing birds (scrub jays) have access to information about what they have stored where and when. This has raised the possibility of mental time travel (MTT) in animals and sparked similar research with other species. Here we caution that such data do not provide convincing evidence for MTT. Examination of characteristics of human MTT (e.g. non-verbal declaration, generativity, developmental prerequisites) points to other avenues as to how a case for animal MTT could be made. In light of the current lack of evidence, however, we maintain that MTT is a uniquely human characteristic.

Mental time travel and the shaping of the human mind

Episodic memory, enabling conscious recollection of past episodes, can be distinguished from semantic memory, which stores enduring facts about the world. Episodic memory shares a core neural network with the simulation of future episodes, enabling mental time travel into both the past and the future. The notion that there might be something distinctly human about mental time travel has provoked ingenious attempts to demonstrate episodic memory or future simulation in non-human animals, but we argue that they have not yet established a capacity comparable to the human faculty. The evolution of the capacity to simulate possible future events, based on episodic memory, enhanced fitness by enabling action in preparation of different possible scenarios that increased present or future survival and reproduction chances. Human language may have evolved in the first instance for the sharing of past and planned future events, and, indeed, fictional ones, further enhancing fitness in social settings.

Behavioural evidence for mental time travel in nonhuman animals

If episodic memory is an adaptation, it must have evolved to benefit present or future survival and reproduction, rather than to provide an accurate record of the past per se. Recent research has documented various links between the ability to construct episodes of the past and imagine potential future episodes, and it has been argued that the former may be a design feature of the latter. Thus, claims about the existence of episodic memory in non-verbal organisms may be evaluated by examining behavioural evidence for foresight. Here we review recent data on foresight in animals and conclude that the evidence to suggest episodic memory so far is equivocal. We suggest specific experimental criteria that could provide stronger evidence. We maintain that there must be uniquely human traits for which there are no animal models and it remains possible that mental time travel depends on several such traits. Identification of what precisely is unique about the human capacity and what is not, can inform us about the nature and evolution of the human capacities.

Early Representational Insight: Twenty-Four-Month-Olds Can Use a Photo to Find an Object in the World

The research reported here shows that under certain circumstances even 24-month-old children can display representational insight. Seventy-nine children participated in 3 studies in which a photo or video presentation could be used to guide their search for a hidden object. Studies 1 and 2 replicated earlier findings of chance performance levels across 4 trials. However, on their first trial, 24-month-olds performed above chance in 3 of 4 conditions in these experiments. Study 3 therefore presented children not with the typical 4 trials in 1 room, but with 1 trial each in 4 different rooms. This manipulation ruled out perseveration errors and resulted in above-chance performance in average mean retrieval rates. These results call for first-trial reanalyses of earlier studies.

Do dogs (Canis familiaris) understand invisible displacement

Domestic dogs (Canis familiaris) perform above chance on invisible displacement tasks despite showing few other signs of possessing the necessary representational abilities. Four experiments investigated how dogs find an object that has been hidden in 1 of 3 opaque boxes. Dogs passed the task under a variety of control conditions, but only if the device used to displace the object ended up adjacent to the target box after the displacement. These results suggest that the search behavior of dogs was guided by simple associative rules rather than mental representation of the objects past trajectory. In contrast, Experiment 5 found that on the same task, 18- and 24-month-old children showed no disparity between trials in which the displacement device was adjacent or nonadjacent to the target box.

Episodic memory versus episodic foresight: similarities and differences

There are logical and empirical grounds that link episodic memory and the ability to imagine future events. In some sense, both episodic memory and episodic foresight may be regarded as two sides of the same capacity to travel mentally in time. After reviewing some of the recent evidence for commonalities, I discuss limits of these parallels. There are fundamental differences between thinking about past and future events that need to be kept in clear view if we are to make progress in understanding the nature of mental time travel. The reviewed evidence suggests that mental time travel is based on a complex system selected not for accuracy about past and future per se, but for fitness benefits. Functional analyses promise to lead to fruitful avenues for future research. Copyright

New evidence for animal foresight

M ental time travel, the ability to project oneself forwards or backwards in time, has recently become a focus of work in comparative psychology (Suddendorf & Busby 2003; Clayton et al. 2003a), neuropsychology (Addis et al. 2007; Szpunar et al. 2007), cognitive psychology (Buckner & Carroll 2007; Hassabis & Maquire 2007; Suddendorf & Corballis 2007a), social psychology (Gilbert & Wilson 2007) and developmental psychology (Atance & O’Neill 2001; Suddendorf & Busby 2005). A controversial aspect of this work is the claim that mental time travel is uniquely human (Suddendorf & Corballis 1997; Suddendorf & Busby 2003; Tulving 2005). A particular suggestion as to what might limit nonhuman animals’ mental time travel into the future is the so-called Bischof-Köhler hypothesis, which states that only humans can flexibly anticipate their own future mental states of need and act now to secure them (Bischof 1978; Bischof-Köhler 1985; Suddendorf & Corballis 1997). Correia et al. (2007) claimed to have refuted, for the first time, the Bischof-Köhler hypothesis in western scrubjays, Aphelocoma californica. In an accompanying article, Roberts (2007), once sceptical of evidence for mental time travel in animals (Roberts 2002), concluded that these results, together with other recent findings (Babb & Crystal 2006; Mulcahy & Call 2006; Naqshbandi & Roberts 2006; Raby et al. 2007), show that some animals can travel mentally in time. Here we warn that each of these studies has attracted critiques identifying methodological and interpretational flaws, and that this new study fares no better. Correia et al. (2007) fed scrub-jays with one type of food for 3 h and then allowed them to cache this and an alternative food. The birds were subsequently prefed with the

The nature of visual self-recognition

Visual self-recognition is often controversially cited as an indicator of self-awareness and assessed with the mirror-mark test. Great apes and humans, unlike small apes and monkeys, have repeatedly passed mirror tests, suggesting that the underlying brain processes are homologous and evolved 14-18 million years ago. However, neuroscientific, developmental, and clinical dissociations show that the medium used for self-recognition (mirror vs photograph vs video) significantly alters behavioral and brain responses, likely due to perceptual differences among the different media and prior experience. On the basis of this evidence and evolutionary considerations, we argue that the visual self-recognition skills evident in humans and great apes are a byproduct of a general capacity to collate representations, and need not index other aspects of self-awareness.

AN EVALUATION OF A SUBURBAN RAILWAY PEDESTRIAN CROSSING SAFETY PROGRAMME

This study evaluated a programme of educational and environmental (access prevention) interventions designed to reduce the incidence of illegal and unsafe crossing of the rail corridor at a suburban station in Auckland, New Zealand. Immediately after the programme of interventions, the proportion of those crossing the rail corridor by walking across the tracks directly rather than using the nearby overbridge had decreased substantially. Three months later, the decrease was even greater. However, the educational and environmental interventions were introduced simultaneously so that the effects of each could not be separated; nor could other unmeasured factors be ruled out. Anonymous surveys administered immediately before and 3 months after the interventions indicated that while awareness of the illegality of walking across the tracks had increased slightly, perception of risk had not changed. This suggests that the educational interventions may have had less effect than the access prevention measures.