Alexandria Boyle

I argue that the function of episodic memory is to store information about the past, against the orthodox view that it is to support imagining the future. I show that episodic memory is epistemically generative, allowing organisms to learn from past events retroactively. This confers adaptive benefits in three domains: Reasoning about the world, skill, and social interaction. Given the role of evolutionary perspectives in comparative research, this argument necessitates a radical shift in the study of episodic memory in nonhumans.

Which animals have episodic memory? One reason this is difficult to answer is that episodic memory could be expected to vary across species, making it hard to give a principled account of what ‘counts’ as an episodic memory system. In this paper, we propose that the investigation of episodic memory in animals should be guided by an account of its proximal proper functions: its most basic selected effects. In short, an animal has episodic memory if it has a memory system with the proximal functions of episodic memory. Whilst there are many accounts of episodic memory’s distal functions, little attention has been paid to its proximal functions. To remedy this, we develop a preliminary account of episodic memory’s proximal functions and use this to evaluate existing evidence about episodic memory in animals.

Mindreaders can ascribe representational states to others. Some can ascribe representational states – states with semantic properties like accuracy-aptness. I argue that within this group of mindreaders, there is substantial room for variation – since mindreaders might differ with respect to the representational format they take representational states to have. Given that formats differ in their formal features and expressive power, the format one takes mental states to have will significantly affect the range of mental state attributions one can make, and the ease or difficulty with which one can make them. I illustrate this by considering what it would be to take mental states to be map-like in format, showing that this would result in a distinctively limited form of mindreading. I close by articulating the significance of this for the emerging picture of great ape mindreading.

Do animals have episodic memory—the kind of memory which gives us rich details about particular past events—or is this uniquely human? This might look like an empirical question, but is attracting increasing philosophical attention. We review relevant behavioural evidence, as well as drawing attention to neuroscientific and computational evidence which has been less discussed in philosophy. Next, we distinguish and evaluate reasons for scepticism about episodic memory in animals. In the process, we articulate three pressing philosophical issues underlying these sceptical arguments, which should be the focus of future work. The Problem of Interspecific Variation asks which differences between humans and animal memory mean that an animal has a variant of episodic memory, and which mean that it has a different kind of memory altogether. The Problem of Functional Variation asks how we should conceptualise the functions of episodic memory and other capacities across species and across evolutionary time. Finally, the Problem of Alternatives asks what, besides episodic memory, might explain the evidence—and how we should evaluate competing explanations.

A common-sense view of mammalian pregnancy treats the fetus as (a) an organism and (b) co-extensive with the approximately baby-shaped entity developing in the uterus. In this paper, I draw on metabolic accounts of the organism to show that (a) and (b) cannot both be correct: either the fetus is not an organism, or it is considerably more extensive than we tend to think, overlapping considerably—perhaps completely—with its mother. Although other accounts of organisms may have different consequences, I argue that they are all likely to put pressure on the idea that the fetus is a roughly baby-shaped organism. I show that this has consequences for understanding the metaphysics of birth, our nature and persistence, and the ethical dynamics of pregnancy.

Episodic memory is the form of memory involved in remembering personally experienced past events. Here, I address two questions about episodic memory’s function: what does episodic memory do for us, and why do we have it? Recent work addressing these questions has emphasized episodic memory’s role in imaginative simulation, criticizing the mnemonic view on which episodic memory is “for” remembering. In this paper, I offer a defense of the mnemonic view by highlighting an underexplored mnemonic function of episodic memory – namely, its role in the encoding, storage and retrieval of the type of information more standardly associated with semantic memory. I argue that in healthy individuals, episodic memory plays a central role in the encoding, storage and retrieval of prototypically semantic information, analogous to the role played by mind palaces in the method of loci, and may have been selected on for this reason. This suggests new directions for studying episodic memory, particularly in nonhuman animals.

Episodic memory—memory for personally experienced past events—seems to afford a distinctive kind of cognitive contact with the past. This makes it natural to think that episodic memory is centrally involved in our understanding of what it is for something to be in the past, or to be located in time—that it is either necessary or sufficient for such understanding. If this were the case, it would suggest certain straightforward evidential connections between temporal cognition and episodic memory in nonhuman animals. In this paper, I argue that matters are more complicated than this. Episodic memory is memory for events and not for the times they occupy. As such, it is dissociable from temporal understanding. This is not to say that episodic memory and temporal cognition are unrelated, but that the relationship between them cannot be straightforwardly captured by claims about necessity and sufficiency. This should inform our theoretical predictions about the manifestations of episodic memory in nonhuman behaviour.

That great apes are the only primates to recognise their reflections is often taken to show that they are self-aware—however, there has been much recent debate about whether the self-awareness in question is psychological or bodily self-awareness. This paper argues that whilst self-recognition does not require psychological self-awareness, to claim that it requires only bodily self-awareness would leave something out. That is that self-recognition requires ‘objective self-awareness’—the capacity for first person thoughts like ‘that's me’, which involve self-identification and so are vulnerable to error through misidentification. This objective self-awareness is distinct from bodily or psychological self-awareness, requires cognitive sophistication and provides the beginnings of a more conceptual self-representation which might play a role in planning, mental time travel and theory of mind.

In dicephalus conjoined twinning, it appears that two heads share a body; in cephalopagus, it appears that two bodies share a head. How many human animals are present in these cases? One answer is that there are two in both cases—conjoined twins are precisely that, conjoined twins. Another is that the number of humans corresponds to the number of bodies—so there is one in dicephalus and two in cephalopagus. I show that both of these answers are incorrect. Prominent accounts of biological individuation, which treat the organism as an integrated whole, reveal that in these and other cases of conjoined twinning the ‘twins’ share a single human animal. This has a number of consequences for the debate about what we are. First, if animalism is true, individuals of our kind can be—and are—profoundly psychologically divided. Second, cephalopagus twinning does not divide animalism from its rivals, as has been claimed. Finally, animalists can reply to a vicious species of the ‘too many thinkers’ problem to which they are allegedly uniquely vulnerable.

Comparative cognitive science often involves asking questions like ‘Do nonhumans have C?’ where C is a capacity we take humans to have. These questions frequently generate unproductive disagreements, in which one party affirms and the other denies that nonhumans have the relevant capacity on the basis of the same evidence. I argue that these questions can be productively understood as questions about natural kinds: do nonhuman capacities fall into the same natural kinds as our own? Understanding such questions in this way has several advantages: it preserves the intuition that these are substantive empirical questions worth asking; it helps us to understand why they so frequently give rise to disagreements of the kind described; and it provides clues about how to diagnose and resolve them.

Episodic memory has a distinctive phenomenology: it involves “mentally reliving” a past event. It has been suggested that characterising episodic memory in terms of this phenomenology makes it impossible to test for in animals, because “purely phenomenological features” cannot be detected in animal behaviour. Against this, I argue that episodic memory's phenomenological features are impure, having both subjective and objective aspects, and so can be behaviourally detected. Insisting on a phenomenological characterisation of episodic memory consequently does nothing to damage the prospects for detecting it in nonhuman animals.

A common‐sense view of mammalian pregnancy treats the fetus as (a) an organism and (b) co‐extensive with the approximately baby‐shaped entity developing in the uterus. In this paper, I draw on metabolic accounts of the organism to show that (a) and (b) cannot both be correct: either the fetus is not an organism, or it is considerably more extensive than we tend to think, overlapping considerably—perhaps completely—with its mother. Although other accounts of organisms may have different consequences, I argue that they are all likely to put pressure on the idea that the fetus is a roughly baby‐shaped organism. I show that this has consequences for understanding the metaphysics of birth, our nature and persistence, and the ethical dynamics of pregnancy.

Which animals have episodic memory? One reason this is difficult to answer is that episodic memory could be expected to vary across species, making it hard to give a principled account of what ‘counts’ as an episodic memory system. In this paper, we propose that the investigation of episodic memory in animals should be guided by an account of its proximal proper functions: its most basic selected effects. In short, an animal has episodic memory if it has a memory system with the proximal functions of episodic memory. Whilst there are many accounts of episodic memory’s distal functions, little attention has been paid to its proximal functions. To remedy this, we develop a preliminary account of episodic memory’s proximal functions and use this to evaluate existing evidence about episodic memory in animals.

Do animals have episodic memory—the kind of memory which gives us rich details about particular past events—or is this uniquely human? This might look like an empirical question, but is attracting increasing philosophical attention. We review relevant behavioural evidence, as well as drawing attention to neuroscientific and computational evidence which has been less discussed in philosophy. Next, we distinguish and evaluate reasons for scepticism about episodic memory in animals. In the process, we articulate three pressing philosophical issues underlying these sceptical arguments, which should be the focus of future work. The Problem of Interspecific Variation asks which differences between humans and animal memory mean that an animal has a variant of episodic memory, and which mean that it has a different kind of memory altogether. The Problem of Functional Variation asks how we should conceptualise the functions of episodic memory and other capacities across species and across evolutionary time. Finally, the Problem of Alternatives asks what, besides episodic memory, might explain the evidence—and how we should evaluate competing explanations.

One of Clayton’s major contributions to our understanding of animal minds has been her work on episodic-like memory. A central reason for the success of this work was its focus on ecological validity: rather than looking for episodic memory for arbitrary stimuli in artificial contexts, focussing on contexts in which episodic memory would serve a biological function such as food caching. This review aims to deepen this insight by surveying the numerous functions that have been proposed for episodic memory, articulating a philosophically grounded framework for understanding what exactly functions are, and drawing on these to make suggestions for future directions in the comparative cognitive psychology of episodic memory. Our review suggests four key insights. First, episodic memory may have more than one function and may have different functions in different species. Second, cross-disciplinary work is key to developing a functional account of episodic memory. Third, there is scope for further theoretical elaboration of proposals relating episodic memory to food caching and, in particular, future-oriented cognition. Finally, learning-related functions suggested by AI (artificial intelligence)-based models are a fruitful avenue for future behavioural research.

Many recent AI systems take inspiration from biological episodic memory. Here, we ask how these ‘episodic-inspired’ AI systems might inform our understanding of biological episodic memory. We discuss work showing that these systems implement some key features of episodic memory whilst differing in important respects, and appear to enjoy behavioural advantages in the domains of strategic decision-making, fast learning, navigation, exploration and acting over temporal distance. We propose that these systems could be used to evaluate competing theories of episodic memory’s operations and function. However, further work is needed to validate them as models of episodic memory and isolate the contributions of their memory systems to their behaviour. More immediately, we propose that these systems have a role to play in directing episodic memory research by highlighting novel or neglected hypotheses as pursuit-worthy. In this vein, we propose that the evidence reviewed here highlights two pursuit-worthy hypotheses about episodic memory’s function: that it plays a role in planning that is independent of future-oriented simulation, and that it is adaptive in virtue of its contributions to fast learning in novel, sparse-reward environments.

Episodic memory is memory for past events. It’s characteristically associated with an experience of ‘mentally replaying’ one’s experiences in the mind’s eye. This biological phenomenon has inspired the development of several ‘experience replay’ algorithms in AI. In this chapter, I ask whether experience replay algorithms might shed light on a puzzle about episodic memory’s function: what does episodic memory contribute to the cognitive systems in which it is found? I argue that experience replay algorithms can serve as idealized models of episodic memory for the purposes of addressing this question. Taking the DQN algorithm as a case study, I suggest that these algorithms provide some support for mnemonic accounts, on which episodic memory’s function lies in the storage, encoding and retrieval of information. By extending and adapting experience replay algorithms, we might gain further insight into episodic memory’s operations and contributions to cognition.

Comparative cognitive science often involves asking questions like ‘Do nonhumans have C?’ where C is a capacity we take humans to have. These questions frequently generate unproductive disagreements, in which one party affirms and the other denies that nonhumans have the relevant capacity on the basis of the same evidence. I argue that these questions can be productively understood as questions about natural kinds: do nonhuman capacities fall into the same natural kinds as our own? Understanding such questions in this way has several advantages: it preserves the intuition that these are substantive empirical questions worth asking; it helps us to understand why they so frequently give rise to disagreements of the kind described; and it provides clues about how to diagnose and resolve them.

Episodic memory is the form of memory involved in remembering personally experienced past events. Here, I address two questions about episodic memory’s function: what does episodic memory do for us, and why do we have it? Recent work addressing these questions has emphasized episodic memory’s role in imaginative simulation, criticizing the mnemonic view on which episodic memory is “for” remembering. In this paper, I offer a defense of the mnemonic view by highlighting an underexplored mnemonic function of episodic memory – namely, its role in the encoding, storage and retrieval of the type of information more standardly associated with semantic memory. I argue that in healthy individuals, episodic memory plays a central role in the encoding, storage and retrieval of prototypically semantic information, analogous to the role played by mind palaces in the method of loci, and may have been selected on for this reason. This suggests new directions for studying episodic memory, particularly in nonhuman animals.

Replications are often taken to play both epistemic and demarcating roles in science: they provide evidence about the reliability of fields’ methods and, by extension, about which fields “count” as scientific. I argue that, in a field characterized by a high degree of theoretical openness and uncertainty, like comparative cognition, replications do not sit well in these roles. Like other experiments conducted under conditions of uncertainty, replications are often equivocal and open to interpretation. As a result, they are poorly placed to deliver clear judgments about the reliability of comparative cognition’s methods or its scientific bona fides. I suggest that this should encourage us to take a broader view of both the nature of scientific progress and the role of replication in comparative cognition.

I argue that the function of episodic memory is to store information about the past, against the orthodox view that it is to support imagining the future. I show that episodic memory is epistemically generative, allowing organisms to learn from past events retroactively. This confers adaptive benefits in three domains: reasoning about the world, skill, and social interaction. Given the role of evolutionary perspectives in comparative research, this argument necessitates a radical shift in the study of episodic memory in nonhumans.

Episodic memory has a distinctive phenomenology: it involves “mentally reliving” a past event. It has been suggested that characterising episodic memory in terms of this phenomenology makes it impossible to test for in animals, because “purely phenomenological features” cannot be detected in animal behaviour. Against this, I argue that episodic memory's phenomenological features are impure, having both subjective and objective aspects, and so can be behaviourally detected. Insisting on a phenomenological characterisation of episodic memory consequently does nothing to damage the prospects for detecting it in nonhuman animals.

That great apes are the only primates to recognise their reflections is often taken to show that they are self-aware—however, there has been much recent debate about whether the self-awareness in question is psychological or bodily self-awareness. This paper argues that whilst self-recognition does not require psychological self-awareness, to claim that it requires only bodily self-awareness would leave something out. That is that self-recognition requires ‘objective self-awareness’—the capacity for first person thoughts like ‘that's me’, which involve self-identification and so are vulnerable to error through misidentification. This objective self-awareness is distinct from bodily or psychological self-awareness, requires cognitive sophistication and provides the beginnings of a more conceptual self-representation which might play a role in planning, mental time travel and theory of mind.

Episodic memory—memory for personally experienced past events—seems to afford a distinctive kind of cognitive contact with the past. This makes it natural to think that episodic memory is centrally involved in our understanding of what it is for something to be in the past, or to be located in time—that it is either necessary or sufficient for such understanding. If this were the case, it would suggest certain straightforward evidential connections between temporal cognition and episodic memory in nonhuman animals. In this paper, I argue that matters are more complicated than this. Episodic memory is memory for events and not for the times they occupy. As such, it is dissociable from temporal understanding. This is not to say that episodic memory and temporal cognition are unrelated, but that the relationship between them cannot be straightforwardly captured by claims about necessity and sufficiency. This should inform our theoretical predictions about the manifestations of episodic memory in nonhuman behaviour.

Mindreaders can ascribe representational states to others. Some can ascribe representational states – states with semantic properties like accuracy-aptness. I argue that within this group of mindreaders, there is substantial room for variation – since mindreaders might differ with respect to the representational format they take representational states to have. Given that formats differ in their formal features and expressive power, the format one takes mental states to have will significantly affect the range of mental state attributions one can make, and the ease or difficulty with which one can make them. I illustrate this by considering what it would be to take mental states to be map-like in format, showing that this would result in a distinctively limited form of mindreading. I close by articulating the significance of this for the emerging picture of great ape mindreading.

In dicephalus conjoined twinning, it appears that two heads share a body; in cephalopagus, it appears that two bodies share a head. How many human animals are present in these cases? One answer is that there are two in both cases—conjoined twins are precisely that, conjoined twins. Another is that the number of humans corresponds to the number of bodies—so there is one in dicephalus and two in cephalopagus. I show that both of these answers are incorrect. Prominent accounts of biological individuation, which treat the organism as an integrated whole, reveal that in these and other cases of conjoined twinning the ‘twins’ share a single human animal. This has a number of consequences for the debate about what we are. First, if animalism is true, individuals of our kind can be—and are—profoundly psychologically divided. Second, cephalopagus twinning does not divide animalism from its rivals, as has been claimed. Finally, animalists can reply to a vicious species of the ‘too many thinkers’ problem to which they are allegedly uniquely vulnerable.