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Being able to abstract relations of similarity is considered one of the hallmarks of human cognition. While previous research has shown that other animals (e.g. primates) can attend to relational similarity, they struggle to focus on object similarity. This is in contrast with humans. And it is precisely the ability to attend to objects that it is argued to make relational reasoning uniquely human. What about invertebrates? Despite earlier studies indicating that bees are capable of learning abstract relationships (e.g. ‘same’ and ‘different’), no research has investigated whether bees can spontaneously attend to relational similarity and whether they can do so when relational matches compete with object matches. To test this, a spatial matching task (with and without competing object matches) previously used with children and great apes was adapted for use with wild-caught bumblebees. When object matches were not present, bumblebees spontaneously used relational similarity. Importantly, when competing object matches were present, bumblebees still focused on relations over objects. These findings indicate that the absence of object bias is also present in invertebrates and suggest that the relational gap between humans and other animals is due to their preference for relations over objects.

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.

Humans are constantly acquiring new information and skills. However, forgetting is also a common phenomenon in our lives. Understanding the lability of memories is critical to appreciate how they are formed as well as forgotten. Here we investigate the lability of chimpanzees' short-term memories and assess what factors cause forgetting in our closest relatives. In two experiments, chimpanzees were presented with a target task, which involved remembering a reward location, followed by the presentation of an interference task-requiring the recollection of a different reward location. The interference task could take place soon after the presentation of the target task or soon before the retrieval of the food locations. The results show that chimpanzees' memories for the location of a reward in a target task were compromised by the presentation of a different food location in an interference task. Critically, the temporal location of the interference task did not significantly affect chimpanzees' performance. These pattern of results were found for both Experiment 1-when the retention interval between the encoding and retrieval of the target task was 60 seconds- and Experiment 2-when the retention interval between the encoding and retrieval of the target task was 30 seconds. We argue that the temporal proximity of the to-be-remembered information and the interference item during encoding is the factor driving chimpanzees' performance in the present studies.

Previous methodologies used to investigate future thinking (i.e., one-step “spoon test”) do not directly assess temporal reasoning. Consequently, the extent to which foresight is required to solve these tasks has been questioned. In the current study, 3-, 4- and 5-year-olds were presented with a two-step “spoon test”: to secure a future need (e.g., play with a marble run game), children first had to obtain a key that allowed them next to access the marbles. By the age of 4 children selected the key; however, it is only by the age of 5 that children reasoned about the temporal sequence of future events and selected the key. Temporal reasoning, memory for the past events and age significantly contributed to predict children’s ability to select the correct item. These findings suggest that temporal reasoning is crucial to assess future thinking and that item-choice measures alone might not involve foresight.

Between 3 and 5 years of age, children develop the ability to plan for their own and others' future needs; however, they have great difficulty predicting future needs that conflict with current ones. Importantly, this ability has only been tested in the domain of physiological states (e.g., thirst). Therefore, it is still an open question whether in a different context preschoolers can disengage from their current needs to secure a different future one. In a Resource Allocation task, 4- and 5-year-olds had to distribute three types of rewards between themselves and another child for either 'right now' or 'tomorrow'. Children's current needs were manipulated by providing them (or not) with their preferred reward at beginning of the task. Only 5-year-olds could predict future needs that conflict with their current ones and act accordingly. Younger children's performance is discussed in the context of temporal and social distance. Statement of contribution What is already known on this subject? By the age of 4, children can plan for their own and others' future needs. Seven-year-old children still have difficulty predicting future physiological needs that conflict with their current ones. What does this study add? In a Resource Allocation task, preschoolers had to share rewards with another child for 'right now' or 'tomorrow'. Children's current needs were manipulated by providing them (or not) with their preferred reward. This study shows that 5-year-olds can predict future (non-physiological) needs that conflict with their current ones.

Episodic memory has been tested in non-human animals using depletion paradigms that assess recollection for the "what", "where" and "when" (i.e., how long ago). This paradigm has not been used with human children, yet doing so would provide another means to explore their episodic memory development. Using a depletion paradigm, preschool-aged children were presented in two trials with a preferred food that was only edible after a short interval and a less-preferred food that was edible after the short and long intervals. Younger (mean = 40 months) and older (mean = 65 months) children tended to choose their preferred food after the short intervals, but did not switch to selecting their less-preferred food after the long intervals. Importantly, their choices did not differ with age. Although older children better remembered "what", "where", and "what is where" than did younger children, neither age group successfully estimated "how long ago" an event occurred. Finally, both age groups spontaneously recalled information about Trial 1. We also analysed the relation between the different measures used in the study but no clear patterns emerged. Results are discussed with respect to the cognitive mechanisms necessary to succeed in depletion paradigms and the measurement of episodic memory more broadly.

Providing adults with relevant information (knowledge that they will be tested at some future time) increases motivation to remember. Research has shown that it is more effective to have this information prior to, rather than after, an encoding phase. We investigated this effect in apes and children in the context of tool-use tasks. In Experiment 1 we presented chimpanzees, orangutans, and bonobos with two tool-use tasks and three different two-tool sets. We had two conditions: prospective (PP) and retrospective (RP). In the PP subjects were shown the task that they would have to solve before they were shown the tools with which they could solve it. In the RP this order was reversed. Apes remembered the location of the useful tool better in the PP than in the RP. In Experiment 2 we presented 3- and 4-year-olds with the same conditions. Both age groups remembered the location of the correct tool in the PP, but only the 4-year-olds did so in the RP. Thus providing apes and preschool children with relevant information prior to, rather than after, the encoding phase enhances memory. These results have important implications for the understanding of the evolution of memory in general, and encoding mechanisms in particular.

In this article we review work on mental imagery in adults and children. We argue that the fundamental issue of how we respond to a stimulus to create a descriptive, propositional scene description, and then render this description into an image is poorly understood. In addition to providing a new framework by which to address this issue, we highlight several other topics within the study of mental imagery that require further investigation. These include inhibiting irrelevant information and making inferences, knowing the difference between reality and imagination (or even beliefs and imagination), and point of view. We conclude by suggesting future directions of study to address these additional topics.

Previous studies on tool using have shown that presenting subjects with certain modifications in the experimental setup can substantially improve their performance. However, procedural modifications (e.g. trap table task) may not only remove task constraints but also simplify the problem conceptually. The goal of this study was to design a variation of the trap-table that was functionally equivalent to the trap-tube task. In this new task, the subjects had to decide where to insert the tool and in which direction the reward should be pushed. We also administered a trap-tube task that allowed animals to push or rake the reward with the tool to compare the subjects’ performance on both tasks. We used a larger sample of subjects than in previous studies and from all the four species of great apes (Gorilla gorilla, Pan troglodytes, Pan paniscus, and Pongo pygmaeus). The results showed that apes performed better in the trap-platform task than in the trap-tube task. Subjects solved the tube task faster than in previous studies and they also preferred to rake in rather than to push the reward out. There was no correlation in the level of performance between both tasks, and no indication of interspecies differences. These data are consistent with the idea that apes may possess some specific causal knowledge of traps but may lack the ability to establish analogical relations between functional equivalent tasks.

Imagine that you are asked to remember a list of words (e.g., “inside” and “consult”). At test you have to recognize which words were in the list. Now imagine that one of the words that you have to recognize is “insult.” Was “insult” in the list? If you respond “yes,” you are making a conjunction error (Underwood and Zimmerman, 1973; Reinitz et al., 1992; Kroll et al., 1996); that is, you incorrectly recognize a novel word (insult), which is made up of parts of two previously studied items (“in,” “sult”), as being part of the previously studied word list. This example illustrates that human episodic memory (memory for events, such as the event of learning a word list) is reconstructive and not an accurate representation of previously experienced events (Roediger, 1996; Tulving, 2005). When recalling an event, we often rely on our store of general knowledge to fill in the gaps, or we confuse information from different sources (Schacter, 2001). Thus, errors (e.g., conjunction errors) constitute the main evidence for reconstructive processes in remembering. Understanding episodic memory as an evolved capacity implies investigating other animals besides humans. Over the last two decades comparative psychologists have mainly studied whether non-human animals (henceforth animals) accurately remember what happened, where and when [Clayton and Dickinson, 1998; see Zentall et al. (2008) and Fortin et al. (2004) for other empirical approaches]. However, the reconstructive nature of episodic memory in animals has received much less attention, although some studies have addressed false memories in animals. For example, artificial memories have been induced by targeted neuronal activation in genetically engineered mice (Liu et al., 2012) and flies (Claridge-Chang et al., 2009); and brain damaged rats behave toward novel objects as if they were familiar (McTighe et al., 2010). However, no research has investigated the reconstructive nature of memory in intact animals, which is crucial to understand the normal functioning of their memory systems. In a recent study published in Current Biology, Hunt and Chittka (2015) did just that: in a series of experiments they investigated whether bees make memory conjunction errors. For the purpose of our argument we will focus on the last experiment, which we consider to be the most convincing one. Authors trained bees to first find a reward (sugar solution) in artificial flowers with a black and white (b/w) pattern (a ring in one group, a grid in another group). Next bees from both groups were rewarded on plain blue flowers but not in the previously rewarded b/w ones. At test 24 h later, bees were presented with the two types of artificial flowers previously experienced and two new types: blue rings and blue grids. Note that whereas for one group the blue grid was the conjunction stimulus and the blue ring only shared one feature with the previously experienced stimuli (i.e., feature stimulus), for the other group the opposite was true. Bees preferred searching in blue flowers. However, they quickly developed a preference for the corresponding conjunction stimulus (e.g., blue ring) over the b/w and the feature stimuli (e.g., blue grid). This design illustrates that bees merge features of previously experienced flowers and rules out simple generalization, as an explanation for bees' responses. But is this preference for the conjunction stimuli in the second half of the experiment evidence for a memory conjunction error? The outcome is different from typical memory conjunction errors in humans. Firstly, humans make memory conjunction errors after short retention intervals, while the bees did not (first experiment; not described above) (e.g., Reinitz et al., 1996; Jones et al., 2007). Secondly, independent of the materials used, humans consistently identify conjunction (new items created by combining features of two previously studied items) and feature (new items created by combining a new feature and a feature of a previously studied item) items as being “old” items more often than they do with totally new items, but less often than they do for actual target (i.e., old) items (Jones and Jacoby, 2001). An explanation based on familiarity accounts for such findings (e.g., Jones et al., 2007). Note that bees were not presented with a new item (i.e., stimuli integrated by two novel features) in any of the experiments, and they preferred the conjunction stimulus (e.g., blue ring pattern for those subjects who experienced “ring” in the first part of the training) to feature (e.g., blue grid) and original stimuli (i.e., b/w ring pattern)—as mentioned above this preference only emerged during the second half of the test. We think that the training procedure might have caused these differences. During the differential reinforcement phase bees learned which flowers contained reward and also which ones did not. However, the change (increase) in associative strength of the positively-reinforced flowers will be greater than the change (decrease) in associative strength in the non-reinforced flowers, because the bees visit more rewarded flowers than non-rewarded flowers (training data in Supplementary Materials). Therefore, after the reversal learning, there is still some positive association left with the firstly-trained flowers, albeit less than with the last-trained flowers (see Menzel, 1969). If we then assume that the associative strength is distributed between the two features of each flower (pattern: ring vs. disk; and color: black vs. blue), then the conjunction stimulus should have an associative strength somewhere between the two original stimuli. With the right combination of associative strengths assigned to the different features (which may have different salience), the results should come out as observed, with a preference for the last-rewarded type (blue), followed by the conjunction stimulus, and an initial avoidance of the feature stimulus and the last-non-rewarded type. A loss of associative strength over time (especially if that drop is steeper for the most recently-rewarded features) would explain why the pattern only arose after 24 h, but not on immediate testing. Does the fact that we can explain Hunt and Chittka's (2015) results using associative learning mean that bees do not make memory conjunction errors? Not necessarily. There is no a priori reason to prefer an associative learning explanation to a more cognitive one. Both the associative learning and familiarity accounts, for example, would predict that training the bees such that both stimuli were rewarded simultaneously (or interleaved) should result in preference for both target stimuli, but might result in preference of conjunctive stimuli over feature stimuli and new stimuli. Finding conditions that distinguish between the two explanations might be difficult, as both could be true at the same time but at different levels of analysis. Whether or not humans and bees retrieve features in the same manner or not, the approach of looking for similarities between the memory systems of humans and other animals by investigating “false memories” is an exciting one. We look forward to a new crop of papers exploiting this novel direction in comparative cognition.

One of the most contested areas in the field of animal cognition is non-human future-oriented cognition. We critically examine key underlying assumptions in the debate, which is mainly preoccupied with certain dichotomous positions, the most prevalent being whether or not ‘real’ future orientation is uniquely human. We argue that future orientation is a theoretical construct threatening to lead research astray. Cognitive operations occur in the present moment and can be influenced only by prior causation and the environment, at the same time that most appear directed towards future outcomes. Regarding the current debate, future orientation becomes a question of where on various continua cognition becomes ‘truly’ future-oriented. We question both the assumption that episodic cognition is the most important process in future-oriented cognition and the assumption that future-oriented cognition is uniquely human. We review the studies on future-oriented cognition in the great apes to find little doubt that our closest relatives possess such ability. We conclude by urging that future-oriented cognition not be viewed as expression of some select set of skills. Instead, research into future-oriented cognition should be approached more like research into social and physical cognition.

In a series of 4 experiments, we tested children's understanding that the causes of their actions must necessarily be attributed to information known prior to (i.e., "pre-action" information), rather than after (i.e., "post-action" information), the completion of their actions. For example, children were shown a dog, asked to get some cheese to feed the dog, and then returned to discover a mouse. In Experiment 1, the majority of 3-, 4-, and 5-year-olds claimed that they had gotten the cheese to feed the mouse. In Experiments 2 and 3, we ruled out the possibilities that (1) children had forgotten the critical "pre-action" information (e.g., "dog"), and (2) children had merely attributed the cause of their action to the most recent item (e.g., "dog") that they had seen. Finally, in Experiment 4, we determined that 7-year-olds, but not 6-year-olds, correctly attributed the cause of their action to the pre-action information, suggesting that this is the age at which children are no longer influenced by associative post-action information when explaining the causes of their actions. These results are discussed in terms of their relevance for causal reasoning, action explanation, and memory.

Humans are able to transcend the present and mentally travel to another time, place, or perspective. Mentally projecting ourselves backwards (i.e., episodic memory) or forwards (i.e., episodic foresight) in time are crucial characteristics of the human memory system. Indeed, over the past few years, episodic memory has been argued to be involved both in our capacity to retrieve our personal past experiences and in our ability to imagine and foresee future scenarios. However, recent theory and findings suggest that semantic memory also plays a significant role in imagining future scenarios. We draw on Tulving’s definition of episodic and semantic memory to provide a critical analysis of their role in episodic foresight tasks described in the developmental literature. We conclude by suggesting future directions of research that could further our understanding of how both episodic memory and semantic memory are intimately connected to episodic foresight.

In this paper we describe a special form of future thinking, termed “episodic foresight” and its relation with episodic and semantic memory. We outline the methodologies that have largely been developed in the last five years to assess this capacity in young children and non-human animals. Drawing on Tulving's definition of episodic and semantic memory, we provide a critical analysis of the role that both types of memory might have on the episodic foresight tasks described in the literature. We conclude by highlighting some unanswered questions and suggesting future directions for research that could further our understanding of how memory is intimately connected to episodic foresight.

Tool-using tasks that require subjects to overcome the obstacles to get a reward have been a major component of research investigating causal knowledge in primates. Much of the debate in this research has focused on whether subjects simply use certain stimulus features or instead use more functionally relevant information regarding the effect that certain features may have on a moving reward. Here, we presented two obstacle tasks, a trap platform and a barrier platform, to 22 great apes. Although perceptually similar, these two tasks contain two perceptually different but functionally equivalent obstacles: a trap and a barrier. In a pre-exposure phase, subjects either experienced an obstacle task or a task without any obstacle. In the transfer phase, all subjects were presented with an obstacle task, either the trap platform or the barrier platform. Our results show that those subjects who received an obstacle task prior to the second task performed better than those who first received a non-obstacle task. The type of obstacle task that subjects received first did not have any effect on their performance in the transfer phase. We suggest that apes possess some knowledge about the effects that obstacles have on slow-moving unsupported objects.

Following encoding, memory remains temporarily vulnerable to disruption. Consolidation refers to offline time-dependent processes that continue after encoding and stabilize, transform or enhance the memory trace. Memory consolidation resulting from sleep has been reported for declarative and non-declarative memories in humans. We first investigated the temporal course of memory retrieval in chimpanzees, bonobos and orangutans. We found that the amount of retrieved information was time dependent: apes' performance degraded after 1 and 2 h, stabilized after 4 h, started to increase after 8 and 12 h and fully recovered after 24 h. Second, we show that although memories during wakefulness were highly vulnerable to interference from events similar to those witnessed during the original encoding event, an intervening period of sleep not only stabilized apes' memories into more permanent ones but also protected them against interference.

Episodic memory, as defined by Tulving, can be described in terms of behavioural elements (what, where and when information) but it is also accompained by an awareness of one’s past (chronesthesia) and a subjective conscious experience (autonoetic awareness). Recent experiments have shown that corvids and rodents recall the where, what and when of an event. This capability has been called episodic-like memory because it only fulfils the behavioural criteria for episodic memory. We tested seven chimpanzees, three orangutans and two bonobos of various ages by adapting two paradigms, originally developed by Clayton and colleagues to test scrub jays. In Experiment 1, subjects were fed preferred but perishable food (frozen juice) and less preferred but non-perishable food (grape). After the food items were hidden, subjects could choose one of them either after 5 min or 1 h. The frozen juice was still available after 5 min but melted after 1 h and became unobtainable. Apes chose the frozen juice significantly more after 5 min and the grape after 1 h. In Experiment 2, subjects faced two baiting events happening at different times, yet they formed an integrated memory for the location and time of the baiting event for particular food items. We also included a memory task that required no temporal encoding. Our results showed that apes remember in an integrated fashion what, where and when (i.e., how long ago) an event happened; that is, apes distinguished between different events in which the same food items were hidden in different places at different times. The temporal control of their choices was not dependent on the familiarity of the platforms where the food was hidden. Chimpanzees’ and bonobos’ performance in the temporal encoding task was age-dependent, following an inverted U-shaped distribution. The age had no effect on the performance of the subjects in the task that required no temporal encoding.

International audience; Using a novel paradigm, Tayloret al.[1] recently investigated whether NewCaledonian crows make causal interventions in comparison to 24-month-oldchildren. They view a causal intervention as the ability, after having onlyobserved a correlation between cause and effect, to produce a novel behaviouralpattern to recreate the same outcome. They conclude that New Caledoniancrows cannot make causal interventions, whereas most children can. Theyalso question whether any previous work has provided evidence for causalinterventions in corvids. We argue that their conclusions are prematurebecause of both methodological and theoretical limitations to their study, andbecause their analysis of previous work is ambiguous.

Summary Determining the memory systems that support nonhuman animals' capacity to remember distant past events is currently the focus an intense research effort and a lively debate [1–3]. Comparative psychology has largely adopted Tulving's framework by focusing on whether animals remember what-where-when something happened (i.e., episodic-like memory) [4–6]. However, apes have also been reported to recall other episodic components [7] after single-trial exposures [8, 9]. Using a new experimental paradigm we show that chimpanzees and orangutans recalled a tool-finding event that happened four times 3 years earlier (experiment 1) and a tool-finding unique event that happened once 2 weeks earlier (experiment 2). Subjects were able to distinguish these events from other tool-finding events, which indicates binding of relevant temporal-spatial components. Like in human involuntary autobiographical memory, a cued, associative retrieval process triggered apes' memories: when presented with a particular setup, subjects instantaneously remembered not only where to search for the tools (experiment 1), but also the location of the tool seen only once (experiment 2). The complex nature of the events retrieved, the unexpected and fast retrieval, the long retention intervals involved, and the detection of binding strongly suggest that chimpanzees and orangutans' memories for past events mirror some of the features of human autobiographical memory.