Children's and Apes' Preparatory Responses to Two Mutually Exclusive Possibilities

Three-year-olds' ability to plan for mutually exclusive future possibilities is limited primarily by their representations of possible plans, not possible events

The ability to prepare for mutually exclusive possible events in the future is essential for everyday decision making. Previous studies have suggested that this ability develops between the ages of 3 and 5 years, and in young children is primarily limited by the ability to represent the set of possible outcomes of an event as "possible". We tested an alternative hypothesis that this ability may be limited by the ability to represent the set of possible actions that could be taken to prepare for those possible outcomes. We adapted the inverted y-shaped tube task of Redshaw and Suddendorf (2016), in which children are asked to catch a marble that is dropped into the top of the tube and can emerge from either the left or right branch of the tube. While 4-year-olds typically place their hands under both openings to catch the marble, preparing for both possible outcomes (optimal action), 3-year-olds often cover only one opening, preparing for only one possible outcome (suboptimal action). In three Experiments, we asked whether first showing children the set of possible actions that could be taken on the tube would enable them to recognize the optimal action that should be used to catch the marble (Experiments 1 and 3, total n = 99 US 3- and 4-year-olds) and enable them to use the optimal action themselves (Experiment 2, n = 96 US 3- and 4-year-olds). We found that 3- and 4-year-olds performed similarly when they were given the opportunity to observe the set of possible actions beforehand. These findings suggest that 3-year-olds' competence at representing mutually exclusive possibilities may be masked by their developing ability to represent and deploy plans to act on these possibilities.

Many preschoolers do not distinguish the possible from the impossible in a marble-catching task

Do preschoolers differentiate events that might and might not happen from events that cannot happen? The current study modified Redshaw & Suddendorf's "Y-shaped tube task" to test how the ability to distinguish mere possibilities from impossibilities emerges over ontogenesis. In the Y-shaped tube task, the experimenter holds a ball above a tube shaped like an upside-down "Y" and asks a participant to catch it. A participant who identifies the two possible paths the ball can take should cover both exits at the bottom of the Y. But children might cover both exits without identifying both possibilities. For example, there are two good places to put hands, so they might just put one hand in each place. This does not require checking whether there is a path from the entrance to each exit. If children cover both exits because they have identified two possible paths for the ball, then they should differentiate exits where it is possible for the ball to come out from impossible exits, where there is no path from the entrance to the exit. In total, 24 36-month-olds and 24 48-month-olds were tested. Less than 20% of 36-month-olds and only about half of 48-month-olds distinguished between possible and impossible exits. Children who do not distinguish the possible from the impossible might not be evaluating possibilities at all. Results converge with existing literature suggesting that action planning that is sensitive to incompatible possibilities often emerges after the fourth birthday.

Young children's conceptualization of empirical disagreement

Chinese and American children aged 5-11 years (total N = 144) heard two child informants make conflicting empirical claims about each of 4 scenarios. For example, one informant claimed that a ball would float when dropped in water whereas the other informant claimed that it would sink. Children were asked to judge whether each informant could be right, and to justify their overall judgment. In both samples, there was a change with age. Older children often said that each informant could be right whereas younger children, especially in China, were more likely to say that only one informant could be right. Nevertheless, in the wake of decisive empirical evidence (e.g., the ball was shown to sink when dropped in water), almost all children, irrespective of age, drew appropriate conclusions about which of the two informants had been right. Thus, with increasing age, children differ in their prospective - but not in their retrospective - appraisal of empirical disagreement. Absent decisive evidence, older children are more likely than younger children to suspend judgment by acknowledging that either of two conflicting claims could be right. We argue that children's tendency to suspend judgment is linked to their developing awareness of empirical uncertainty, as expressed both in the justifications they give when judging the disagreement and in their own beliefs about the scenarios. Implications for children's understanding of disagreement are discussed.

Don't you see the possibilities? Young preschoolers may lack possibility concepts

Preschoolers struggle to solve problems when they have to consider what might and might not happen. Instead of planning for all open possibilities, they simulate one possibility and treat it as the fact of the matter. Why? Are scientists asking them to solve problems that outstrip their executive capacity? Or do children lack the logical concepts needed to take multiple conflicting possibilities into account? To address this question, task demands were eliminated from an existing measure of children's ability to think about mere possibilities. One hundred nineteen 2.5- to 4.9-year-olds were tested. Participants were highly motivated but could not solve the problem. Bayesian analysis revealed strong evidence that reducing task demands while holding reasoning demands constant did not change performance. Children's struggles with the task cannot be explained by these task demands. Results are consistent with the hypothesis that children struggle because they cannot deploy possibility concepts that allow them to mark representations as merely possible. RESEARCH HIGHLIGHTS: Preschoolers are surprisingly irrational when faced with problems that ask them to consider what might and might not be the case. These irrationalities could arise from deficits in children's logical reasoning capacities or from extraneous task demands. This paper describes three plausible task demands. A new measure is introduced that preserves logical reasoning demands while eliminating all three extraneous task demands. Eliminating these task demands does not change performance. These task demands are not likely a cause of children's irrational behavior.

The scope and role of deduction in infant cognition

The origins of the human capacity for logically structured thought are still a mystery. Studies on young humans, which can be particularly informative, present conflicting results. Infants seem able to generate competing hypotheses1,2,3 and monitor the certainty or probability of one-shot outcomes,4,5,6,7,8 suggesting the existence of an articulated language of thought.9 However, sometimes toddlers10 and even children younger than 411,12,13,14 fail tasks seemingly requiring the same representational abilities. One fundamental test for the presence of logical abilities is the concept of disjunction as a way into the conception of alternative possibilities, and of disjunctive elimination as a way to prune them. Here, we document their widespread presence in 19-month-old infants. In a word-referent association task, both bilingual and monolingual infants display a pattern of oculomotor inspection previously found to be a hallmark of disjunctive reasoning in adults and children,15,16 showing that the onset of logical reasoning is not crucially dependent on language experience. The pattern appears when targets are novel, but also when both objects and words are known, though likely not yet sedimented into a mature lexicon. Disjunctive reasoning also surfaces in a non-linguistic location search task, not prompted by violated expectations, showing that infants reason by elimination spontaneously. Together, these results help answer long-standing empirical and philosophical puzzles about the role of logic in early knowledge development, suggesting that by increasing confidence in some options while eliminating alternatives, logic provides scaffolding for the organization of knowledge about the world, language, and language-world relations.

The Best-Case Heuristic: Relative Optimism in Relationships, Politics, and a Global Health Pandemic

In four experiments covering three different life domains, participants made future predictions in what they considered the most realistic scenario, an optimistic best-case scenario, or a pessimistic worst-case scenario (N = 2,900 Americans). Consistent with a best-case heuristic, participants made "realistic" predictions that were much closer to their best-case scenario than to their worst-case scenario. We found the same best-case asymmetry in health-related predictions during the COVID-19 pandemic, for romantic relationships, and a future presidential election. In a fully between-subject design (Experiment 4), realistic and best-case predictions were practically identical, and they were naturally made faster than the worst-case predictions. At least in the current study domains, the findings suggest that people generate "realistic" predictions by leaning toward their best-case scenario and largely ignoring their worst-case scenario. Although political conservatism was correlated with lower covid-related risk perception and lower support of early public-health interventions, the best-case prediction heuristic was ideologically symmetric.

Do chimpanzees reason logically?

Psychologists disagree about the development of logical concepts such as or and not. While some theorists argue that infants reason logically, others maintain that logical inference is contingent on linguistic abilities and emerges around age 4. In this Registered Report, we conducted five experiments on logical reasoning in chimpanzees. Subjects (N = 16; 10 females; M = 24 years) participated in the same setup that has been administered to children: the two-, three-, and four-cup-task. Chimpanzees performed above chance in the two-cup-, but not in the three-cup-task. Furthermore, chimpanzees selected the logically correct option more often in the test than the control condition of the four-cup-task. We discuss possible interpretations of these findings and conclude that our results are most consistent with non-deductive accounts.

The acquisition of English modal constructions: a corpus-based analysis

The English modal system is complex, exhibiting many-to-one, and one-to-many, form-function mappings. Usage-based approaches emphasise the role of the input in acquisition but rarely address the impact of form-function mappings on acquisition. To test whether consistent form-function mappings facilitate acquisition, we analysed two dense mother-child corpora at age 3 and 4. We examined the influence on acquisition of input features including form-function mapping frequency and the number of functions a modal signifies, using innovative methodological controls for other aspects of the input (e.g., form frequency) and child characteristics (e.g., age as a proxy for socio-cognitive development). The children were more likely to produce the frequent modals and form-function mappings of their input but modals with fewer functions in caregiver speech did not promote acquisition of these forms. Our findings support usage-based approaches to language acquisition and demonstrate the importance of applying appropriate controls when investigating relationships between input and development.

Thinking about possibilities: mechanisms, ontogeny, functions and phylogeny

Humans possess the remarkable capacity to imagine possible worlds and to demarcate possibilities and impossibilities in reasoning. We can think about what might happen in the future and consider what the present would look like had the past turned out differently. We reason about cause and effect, weigh up alternative courses of action and regret our mistakes. In this theme issue, leading experts from across the life sciences provide ground-breaking insights into the proximate questions of how thinking about possibilities works and develops, and the ultimate questions of its adaptive functions and evolutionary history. Together, the contributions delineate neurophysiological, cognitive and social mechanisms involved in mentally simulating possible states of reality; and point to conceptual changes in the understanding of singular and multiple possibilities during human development. The contributions also demonstrate how thinking about possibilities can augment learning, decision-making and judgement, and highlight aspects of the capacity that appear to be shared with non-human animals and aspects that may be uniquely human. Throughout the issue, it becomes clear that many developmental milestones achieved during childhood, and many of the most significant evolutionary and cultural triumphs of the human species, can only be understood with reference to increasingly complex reasoning about possibilities. This article is part of the theme issue 'Thinking about possibilities: mechanisms, ontogeny, functions and phylogeny'.

The importance of thinking about the future in culture and cumulative cultural evolution

Thinking about possibilities plays a critical role in the choices humans make throughout their lives. Despite this, the influence of individuals' ability to consider what is possible on culture has been largely overlooked. We propose that the ability to reason about future possibilities or prospective cognition, has consequences for cultural change, possibly facilitating the process of cumulative cultural evolution. In particular, by considering potential future costs and benefits of specific behaviours, prospective cognition may lead to a more flexible use of cultural behaviours. In species with limited planning abilities, this may lead to the development of cultures that promote behaviours with future benefits, circumventing this limitation. Here, we examine these ideas from a comparative perspective, considering the relationship between human and nonhuman assessments of future possibilities and their cultural capacity to invent new solutions and improve them over time. Given the methodological difficulties of assessing prospective cognition across species, we focus on planning, for which we have the most data in other species. Elucidating the role of prospective cognition in culture will help us understand the variability in when and how we see culture expressed, informing ongoing debates, such as that surrounding which social learning mechanisms underlie culture. This article is part of the theme issue 'Thinking about possibilities: mechanisms, ontogeny, functions and phylogeny'.

The pupillometry of the possible: an investigation of infants' representation of alternative possibilities

Contrasting possibilities has a fundamental adaptive value for prediction and learning. Developmental research, however, has yielded controversial findings. Some data suggest that preschoolers might have trouble in planning actions that take into account mutually exclusive possibilities, while other studies revealed an early understanding of alternative future outcomes based on infants' looking behaviour. To better understand the origin of such abilities, here we use pupil dilation as a potential indicator of infants' representation of possibilities. Ten- and 14-month-olds were engaged in an object-identification task by watching video animations where three different objects with identical top parts moved behind two screens. Importantly, a target object emerged from one of the screens but remained in partial occlusion, revealing only its top part, which was compatible with a varying number of possible identities. Just as adults' pupil diameter grows monotonically with the amount of information held in memory, we expected that infants' pupil size would increase with the number of alternatives sustained in memory as candidate identities for the partially occluded object. We found that pupil diameter increased with the object's potential identities in 14- but not in 10-month-olds. We discuss the implications of these results for the foundation of humans' capacities to represent alternatives. This article is part of the theme issue 'Thinking about possibilities: mechanisms, ontogeny, functions and phylogeny'.

Young children share imagined possibilities: evidence for an early-emerging human competence

Children's ability to reason about junctures leading to two different destinations emerges slowly, with convergent evidence for a conceptual watershed at approximately 4 years. Young children and great apes misrepresent such junctures, planning for only one expected outcome. However, singular possibilities, as opposed to two mutually exclusive possibilities, are readily imagined, shared and acted upon by 2- and 3-year-olds. Analysis of three domains supports this claim. First, 2- and 3-year-olds respond appropriately to pretend spatial displacements enacted for them by a play partner. Second, they not only respond accurately to claims regarding an alleged but unwitnessed spatial displacement, they also ask their interlocutors about the possible whereabouts of missing objects and absent persons. Third, in ordinary conversation, they appropriately mark some of their assertions as possibilities rather than actualities. In summary, although the ability to reason about mutually inconsistent possibilities develops slowly in the preschool years, the ability to imagine and share information about possibilities is evident among 2- and 3-year-olds. Nothing comparable has been observed in great apes. Young children's ability to entertain shared possibilities diverges from that of non-human primates well before any potential watershed at 4 years with respect to the understanding of mutually exclusive possibilities. This article is part of the theme issue 'Thinking about possibilities: mechanisms, ontogeny, functions and phylogeny'.

The best game in town: The reemergence of the language-of-thought hypothesis across the cognitive sciences

Mental representations remain the central posits of psychology after many decades of scrutiny. However, there is no consensus about the representational format(s) of biological cognition. This paper provides a survey of evidence from computational cognitive psychology, perceptual psychology, developmental psychology, comparative psychology, and social psychology, and concludes that one type of format that routinely crops up is the language-of-thought (LoT). We outline six core properties of LoTs: (i) discrete constituents; (ii) role-filler independence; (iii) predicate-argument structure; (iv) logical operators; (v) inferential promiscuity; and (vi) abstract content. These properties cluster together throughout cognitive science. Bayesian computational modeling, compositional features of object perception, complex infant and animal reasoning, and automatic, intuitive cognition in adults all implicate LoT-like structures. Instead of regarding LoT as a relic of the previous century, researchers in cognitive science and philosophy-of-mind must take seriously the explanatory breadth of LoT-based architectures. We grant that the mind may harbor many formats and architectures, including iconic and associative structures as well as deep-neural-network-like architectures. However, as computational/representational approaches to the mind continue to advance, classical compositional symbolic structures - that is, LoTs - only prove more flexible and well-supported over time.

You can't change the past: Children's recognition of the causal asymmetry between past and future events

This study explored children's causal reasoning about the past and future. U.S. adults (n = 60) and 3-to-6-year-olds (n = 228) from an urban, middle-class population (49% female; ~45% white) participated between 2017 and 2019. Participants were told three-step causal stories and asked about the effects of a change to the second event. Given direct interventions on the second event, children of all ages judged that the past event still occurred, suggesting even preschoolers understand time is irreversible. However, children reasoned differently when told that the second event did not occur, with no specific cause. In this case, 6-year-olds and adults inferred that the past event also did not occur. In both conditions, inferences that future events would change emerged gradually between 4 and 6.

Young children spontaneously devise an optimal external solution to a cognitive problem

Metacognition plays an essential role in adults' cognitive offloading decisions. Despite possessing basic metacognitive capacities, however, preschool-aged children often fail to offload effectively. Here, we introduced 3- to 5-year-olds to a novel search task in which they were unlikely to perform optimally across trials without setting external reminders about the location of a target. Children watched as an experimenter first hid a target in one of three identical opaque containers. The containers were then shuffled out of view before children had to guess where the target was hidden. In the test phase, children could perform perfectly by simply placing a marker in a transparent jar attached to the target container prior to shuffling, and then later selecting the marked container. Children of all ages used this external strategy above chance levels if they had seen it demonstrated to them, but only the 4- and 5-year-olds independently devised the strategy to improve their future performance. These results suggest that, when necessary for optimal performance, even 4- and 5-year-olds can use metacognitive knowledge about their own future uncertainty to deploy effective external solutions.

Do Monkeys and Young Children Understand Exclusive "Or" Relations? A Commentary on Ferrigno et al. (2021)

Ferrigno et al. (2021) claim to provide evidence that monkeys can reason through the disjunctive syllogism (given A or B, not A, therefore B) and conclude that monkeys therefore understand logical "or" relations. Yet their data fail to provide evidence that the baboons they tested understood the exclusive "or" relations in the experimental task. For two mutually exclusive possibilities-A or B-the monkeys appeared to infer that B was true when A was shown to be false, but they failed to infer that B was false when A was shown to be true. In our own research, we recently found an identical response pattern in 2.5- to 4-year-old children, whereas 5-year-olds demonstrated that they could make both inferences. The monkeys' and younger children's responses are instead consistent with an incorrect understanding of A and B as having an inclusive "or" relation. Only the older children provided compelling evidence of representing the exclusive "or" relation between A and B.

Chimpanzees consider alternative possibilities

Humans reason not only about actual events (what is), but also about possible events (what could be). Many key operations of human cognition involve the representation of possibilities, including moral judgment, future planning, and causal understanding¹. But little is known about the evolutionary roots of this kind of thought. Humans' closest relatives, chimpanzees, possess several cognitive abilities that are closely related to reasoning about alternatives: they plan for the future², evaluate other's actions³, and reason causally⁴. However, in the first direct test of the ability to consider alternatives, Redshaw and Suddendorf⁵ claim that chimpanzees are not able to represent alternative possibilities. Here, using a novel method, we challenge this conclusion: our results suggest that, like human cognition, chimpanzee thought is not limited to what is, but also involves reasoning about what could be the case.

Toddlers learn and flexibly apply multiple possibilities

The ability to consider multiple possibilities forms the basis for a wide variety of human-unique cognitive capacities. When does this skill develop? Previous studies have narrowly focused on children's ability to prepare for incompatible future outcomes. Here, we investigate this capacity in a causal learning context. Adults (N = 109) and 18- to 30-month olds (N = 104) observed evidence that was consistent with two hypotheses, each occupying a different level of abstraction (individual vs. relational causation). Results suggest that adults and toddlers identified multiple candidate causes for an effect, held these possibilities in mind, and flexibly applied the appropriate hypothesis to inform subsequent inferences. These findings challenge previous suggestions that the ability to consider multiple alternatives does not emerge until much later in development.

Ventral-Dorsal Subregions in the Posterior Cingulate Cortex Represent Pay and Interest, Two Key Attributes of Job Value

Career choices affect not only our financial status but also our future well-being. When making these choices, individuals evaluate their willingness to obtain a job (i.e., job values), primarily driven by simulation of future pay and interest. Despite the importance of these decisions, their underlying neural mechanisms remain unclear. In this study, we examined the neural representation of pay and interest. Forty students were presented with 80 job names and asked to evaluate their job values while undergoing functional magnetic resonance imaging (fMRI). Following fMRI, participants rated the jobs in terms of pay and interest. The fMRI data revealed that the ventromedial prefrontal cortex (vmPFC) was associated with job value representation, and the ventral and dorsal regions of the posterior cingulate cortex (PCC) were associated with pay and interest representations, respectively. These findings suggest that the neural computations underlying job valuation conform to a multi-attribute decision-making framework, with overall value signals represented in the vmPFC and the attribute values (i.e., pay and interest) represented in specific regions outside the vmPFC, in the PCC. Furthermore, anatomically distinct representations of pay and interest in the PCC may reflect the differing roles of the two subregions in future simulations.

Understanding Human Cognitive Uniqueness

Humanity has regarded itself as intellectually superior to other species for millennia, yet human cognitive uniqueness remains poorly understood. Here, we evaluate candidate traits plausibly underlying our distinctive cognition (including mental time travel, tool use, problem solving, social cognition, and communication) as well as domain generality, and we consider how human cognitive uniqueness may have evolved. We conclude that there are no traits present in humans and absent in other animals that in isolation explain our species' superior cognitive performance; rather, there are many cognitive domains in which humans possess unusually potent capabilities compared to those found in other species. Humans are flexible cognitive all-rounders, whose proficiency arises through interactions and reinforcement between cognitive domains at multiple scales.

What You Don't Know Can Hurt You: Uncertainty Impairs Executive Function

Three studies demonstrated that situational uncertainty impairs executive function on subsequent unrelated tasks. Participants were randomly assigned to either uncertain situations (not knowing whether they would have to give a speech later, Studies 1-2; uncertain about how to complete a task, Study 3) or control conditions. Uncertainty caused poor performance on tasks requiring executive function that were unrelated to the uncertainty manipulation. Uncertainty impaired performance even more than certainty of negative outcomes (might vs. definitely will have to make a speech). A meta-analysis of the experimental studies in this package found that the effect is small and reliable. One potential explanation for this effect of uncertainty on executive function is that uncertainty is a cue for conserving effort.

It's in the bag: mobile containers in human evolution and child development

Mobile containers are a keystone human innovation. Ethnographic data indicate that all human groups use containers such as bags, quivers and baskets, ensuring that individuals have important resources at the ready and are prepared for opportunities and threats before they materialize. Although there is speculation surrounding the invention of carrying devices, the current hard archaeological evidence only reaches back some 100,000 years. The dearth of ancient evidence may reflect not only taphonomic processes, but also a lack of attention to these devices. To begin investigating the origins of carrying devices we focus on exploring the basic cognitive processes involved in mobile container use and report an initial study on young children's understanding and deployment of such devices. We gave 3- to 7-year-old children (N = 106) the opportunity to spontaneously identify and use a basket to increase their own carrying capacity and thereby obtain more resources in the future. Performance improved linearly with age, as did the likelihood of recognizing that adults use mobile carrying devices to increase carrying capacity. We argue that the evolutionary and developmental origins of mobile containers reflect foundational cognitive processes that enable humans to think about their own limits and compensate for them.

Episodic memory in nonhuman animals?

Experimental psychologist Jonathan Crystal and evolutionary psychologist Thomas Suddendorf debate with nonhuman animals experience human-like episodic memory.

It is about time: Conceptual and experimental evaluation of the temporal cognitive mechanisms in mental time travel

Mental time travel (MTT) is the ability that allows humans to mentally project themselves backwards in time to remember past events (i.e., episodic memory) or forwards in time to imagine future events (i.e., future thinking). Despite empirical evidence showing that animals might possess MTT abilities, some still claim that this ability is uniquely human. Recent debates have suggested that it is the temporal cognitive mechanism (i.e., ability to represent the sense of past and future) that makes MTT uniquely human. Advances in the field have been constrained by a lack of comparative data, methodological shortcomings that prevent meaningful comparisons, and a lack of clear conceptualizations of the temporal cognitive mechanism. Here I will present a comprehensive review into MTT in humans and animals-with a particular focus on great apes. I will examine three of the most prominent and influential theoretical models of human MTT. Drawing on these accounts, I suggest that a basic way of understanding time might be shared across species, however culture and language will play a critical role at shaping the way we elaborate mental representations about past and future events. This article is categorized under: Cognitive Biology > Evolutionary Roots of Cognition Psychology > Comparative Psychology.

Children's future-oriented cognition

Children's future-oriented cognition has become a well-established area of research over the last decade. Future-oriented cognition encompasses a range of processes, including those involved in conceiving the future, imagining and preparing for future events, and making decisions that will affect how the future unfolds. We consider recent empirical advances in the study of such processes by outlining key findings that have yielded a clearer picture of how future thinking emerges and changes over childhood. Our interest in future thinking stems from a broader interest in temporal cognition, and we argue that a consideration of developmental changes in how children understand and represent time itself provides a valuable framework in which to study future-oriented cognition.

Temporal Junctures in the Mind

Humans can imagine what happened in the past and what will happen in the future, but also what did not happen and what might happen. We reflect on envisioned events from alternative timelines, while knowing that we only ever live on one timeline. Considering alternative timelines rests on representations of temporal junctures, or points in time at which possible versions of reality diverge. These representations become increasingly sophisticated over childhood, first enabling preparation for mutually exclusive future possibilities and later the experience of counterfactual emotions like regret. By contrast, it remains unclear whether non-human animals represent temporal junctures at all. The emergence of these representations may have been a prime mover in human evolution.

The Acquisition of Modal Concepts

Sometimes we accept propositions, sometimes we reject them, and sometimes we take propositions to be worth considering but not yet established, as merely possible. The result is a complex representation with logical structure. Is the ability to mark propositions as merely possible part of our innate representational toolbox or does it await development, perhaps relying on language acquisition? Several lines of inquiry show that preverbal infants manage possibilities in complex ways, while others find that preschoolers manage possibilities poorly. Here, we discuss how this apparent conflict can be resolved by distinguishing modal representations of possibility, which mark possibility symbolically, from minimal representations of possibility, which do not encode any modal status and need not have a logical structure.

Thinking about thinking about time

Hoerl & McCormack (H&M) discuss the possible function of meta-representations in temporal cognition but ultimately take an agnostic stance. Here we outline the fundamental role that we believe meta-representations play. Because humans know that their representations of future events are just representations, they are in a position to compensate for the shortcomings of their own foresight and to prepare for multiple contingencies.

Innovative problem solving in great apes: the role of visual feedback in the floating peanut task

Nonhuman great apes show remarkable behavioural flexibility. Some individuals are even able to use water as a tool: They spit water into a vertical tube to make a peanut float upwards until it comes into reach (floating peanut task; FPT). In the current study, we used the FPT to investigate how visual feedback, an end-state demonstration and a social demonstration affect task performance in nonhuman great apes in three experiments. Our results indicate that apes who had acquired the solution with a clear tube maintained it with an opaque one. However, apes starting with an opaque tube failed to solve the task. Additionally, facing the peanut floating on a water-filled tube (i.e., an end-state demonstration) promoted success independent on the availability of visual feedback. Moreover, experiencing how water was poured into the tube either by a human demonstrator or by a water tap that had been opened either by the ape or a human did not seem to be of further assistance. First, this study suggests that great apes require visual feedback for solving the FPT, which is no longer required after the initial acquisition. Second, some subjects benefit from encountering the end-state, a finding corroborating previous studies.

The Functions of Prospection - Variations in Health and Disease

Much of human life revolves around anticipating and planning for the future. It has become increasingly clear that this capacity for prospective cognition is a core adaptive function of the mind. Here, we review the role of prospection in two key functional domains: goal-directed behavior and flexible decision-making. We then survey and categorize variations in prospection, with a particular focus on functional impact in clinical psychological conditions and neurological disorders. Finally, we suggest avenues for future research into the functions of prospection and the manner in which these functions can shift toward maladaptive outcomes. In doing so, we consider the conceptualization and measurement of prospection, as well as novel approaches to its augmentation in healthy people and managing its alterations in a clinical context.

Comparing chimpanzees' preparatory responses to known and unknown future outcomes

When humans plan for the future, we recognize not only that one particular event may occur, but that the future can have different, mutually exclusive possible outcomes. A recent study by Suddendorf et al (Suddendorf 2017 Biol. Lett. 13, 20170170 (doi:10.1098/rsbl.2017.0170)) suggests that young children (less than 3 years) and apes lack this capacity, as demonstrated by their failure to cover each of two tube openings to ensure catching an object that would drop randomly from one of the tubes. Before drawing conclusions based on these negative results, however, it is important to assess subjects' failures and test the reliability of the task itself. To explore whether the apes' performance resulted from an inability to represent mutually exclusive futures or from extraneous factors related to the task, we replicated the methods of Suddendorf et al (Suddendorf 2017 Biol. Lett. 13, 20170170 (doi:10.1098/rsbl.2017.0170)) with a group of six chimpanzees but included a key control condition in which subjects were expected to cover both tubes on every trial (i.e. the rewards would consistently emerge from both tubes). We show that even in this straightforward condition in which the outcome of the trial was known, only four of the six subjects ever covered both tubes, typically doing so after a minimum of 17 trials, and often reverting back to covering one tube on later trials. We conclude that this task is not valid for testing the ability to represent mutually exclusive futures. We discuss what potential factors may explain the results and outline a new suggested method to continue testing for this capacity in the future.

Thinking in and about time: A dual systems perspective on temporal cognition

We outline a dual systems approach to temporal cognition, which distinguishes between two cognitive systems for dealing with how things unfold over time – a temporal updating system and a temporal reasoning system – of which the former is both phylogenetically and ontogenetically more primitive than the latter, and which are at work alongside each other in adult human cognition. We describe the main features of each of the two systems, the types of behavior the more primitive temporal updating system can support, and the respects in which it is more limited than the temporal reasoning system. We then use the distinction between the two systems to interpret findings in comparative and developmental psychology, arguing that animals operate only with a temporal updating system and that children start out doing so too, before gradually becoming capable of thinking and reasoning about time. After this, we turn to adult human cognition and suggest that our account can also shed light on a specific feature of humans’ everyday thinking about time that has been the subject of debate in the philosophy of time, which consists in a tendency to think about the nature of time itself in a way that appears ultimately self-contradictory. We conclude by considering the topic of intertemporal choice, and argue that drawing the distinction between temporal updating and temporal reasoning is also useful in the context of characterizing two distinct mechanisms for delaying gratification.

Young children's capacity to imagine and prepare for certain and uncertain future outcomes

The current study used a minimalist paradigm to examine young children's capacity to imagine and prepare for certain and uncertain immediate future outcomes. In a counterbalanced order, 2.5-year-old children (N = 32) completed twelve trials each of two tasks: (1) the forked tube task, which assessed their ability to cover two possible tube exits to ensure they would catch a single target with an uncertain future trajectory, and (2) the double tube task, which assessed their ability to cover two separate tube exits to ensure they would catch two targets with certain future trajectories. Even though the optimal preparatory action was the same across both tasks, children were much more likely to spontaneously and consistently demonstrate this action in the double tube task than the forked tube task. Children's responses were unaffected by the number of targets seen in the demonstration phase, and instead appeared to be based on the particular contingencies of each apparatus. These results are consistent with the possibility that young children specifically struggle to imagine and prepare for mutually exclusive versions of uncertain future events.

Development of Children's Use of External Reminders for Hard-to-Remember Intentions

This study explored under what conditions young children would set reminders to aid their memory for delayed intentions. A computerized task requiring participants to carry out delayed intentions under varying levels of cognitive load was presented to 63 children (aged between 6.9 and 13.0 years old). Children of all ages demonstrated metacognitive predictions of their performance that were congruent with task difficulty. Only older children, however, set more reminders when they expected their future memory performance to be poorer. These results suggest that most primary school-aged children possess metacognitive knowledge about their prospective memory limits, but that only older children may be able to exercise the metacognitive control required to translate this knowledge into strategic reminder setting.

Misconceptions about adaptive function

Mahr & Csibra (M&C) fail to make the important distinction between why a trait originally evolved, why it was maintained over time, and what its current utility is. Here we point out that episodic memory may have originally evolved as a by-product of a general metarepresentational capacity, and that it may have current functions beyond the communicative domain.

Preparatory responses to socially determined, mutually exclusive possibilities in chimpanzees and children

The capacity to imagine and prepare for alternative future possibilities is central to human cognition. Recent research suggests that between age 2 and 4 children gradually begin to demonstrate a capacity to prepare for two simple, mutually exclusive alternatives of an immediate future event. When children were given the opportunity to catch a target an experimenter dropped into an inverted Y-shaped tube, 2-year olds-as well as great apes-tended to cover only one of the exits, whereas 4-year-olds spontaneously and consistently prepared for both possible outcomes. Here we gave children, age 2 to 4 years, and chimpanzees a different opportunity to demonstrate potential competence. Given that social behaviour is particularly full of uncertainty, we developed a version of the task where the outcome was still unpredictable yet obviously controlled by an experimenter. Participants could ensure they would catch the target by simply covering two tube exits. While 4-year-olds demonstrated competence, chimpanzees and the younger children instead tended to cover only one exit. These results substantiate the conclusion that the capacity for simultaneous preparation for mutually exclusive event outcomes develops relatively late in children and they are also in line with the possibility that our close animal relatives lack this capacity.

Future Thinking: Children But Not Apes Consider Multiple Possibilities

When anticipating the future, we draw on our past experience but must take uncertainty into account; for example, while preparing for a trip, we might pack a raincoat and sunglasses because of unpredictable weather. New research shows that the ability to plan for multiple future possibilities may be present in human children from as early as 3-4 years of age, but appears to be lacking in non-human apes.