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Phylogenetic tree depicting the evolutionary relationship between cephalopods and the more commonly studied vertebrates, corvids, and great apes (image sources: © CCBY-SA: gastropod, echinoderm, chiton, reptile ancestor; © CCBY-NC-ND: cuttlefish; © CCBYSA-NC: worm ancestor; © jenesesimre, stock.adobe.com: octopus, squid, arthropod, bivalve; © artbalitskiy, stock.adobe. com: ape, corvid, fish, amphibian, reptile).
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The soft-bodied cephalopods including octopus, cuttlefish, and squid are broadly considered to be the most cognitively advanced group of invertebrates. Previous research has demonstrated that these large-brained molluscs possess a suite of cognitive attributes that are comparable to those found in some vertebrates, including highly developed percep...
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... beyond vertebrates, new ndings amongst invertebrates provides further evidence that intelligence has evolved independently multiple times. A substantial amount of this evidence is emerging from one major group of invertebrates, the coleoid cephalopods, which diverged radically from vertebrates over 550 million years ago (Fig. 1). The coleoid cephalopods (henceforth cephalopods), which include octopus, cuttlesh, and squid have the most centralised and largest nervous system of all invertebrates, with a brain to body size ratio greater than most sh and reptiles (Packard, 1972;Nixon & Young, 2003). Such ndings are intriguing given that many of the molluscan ...
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... required to support the emergence of complex cognition because they diverged from the vertebrate lineage over 550 million years ago. The common ancestor of cephalopods and vertebrates was substantially more rudimentary than the common ancestor of birds and mammals and likely resembled a wormlike creature with a simple nervous system (Fig. 1). Consequently, cephalopods deviate drastically from vertebrates and thus exhibit signicantly different characteristics from the more commonly studied large-brained vertebrates. Specically, they have a highly carnivorous diet, a brief developmental period, and reduced longevity. Comparative data between cephalopods and the more ...
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... beyond vertebrates, new findings amongst invertebrates provides further evidence that intelligence has evolved independently multiple times. A substantial amount of this evidence is emerging from one major group of invertebrates, the coleoid cephalopods, which diverged radically from vertebrates over 550 million years ago (Fig. 1). The coleoid cephalopods (henceforth cephalopods), which include octopus, cuttlefish, and squid have the most centralised and largest nervous system of all invertebrates, with a brain to body size ratio greater than most fish and reptiles (Packard, 1972;Nixon & Young, 2003). Such findings are intriguing given that many of the molluscan ...
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... required to support the emergence of complex cognition because they diverged from the vertebrate lineage over 550 million years ago. The common ancestor of cephalopods and vertebrates was substantially more rudimentary than the common ancestor of birds and mammals and likely resembled a wormlike creature with a simple nervous system (Fig. 1). Consequently, cephalopods deviate drastically from vertebrates and thus exhibit significantly different characteristics from the more commonly studied large-brained vertebrates. Specifically, they have a highly carnivorous diet, a brief developmental period, and reduced longevity. Comparative data between cephalopods and the more ...
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The Cambrian information revolution describes how biotically driven increases in signals, sensory abilities, behavioral interactions, and landscape spatial complexity drove a rapid increase in animal cognition concurrent with the Cambrian radiation. Here, we compare cognitive complexity in Cambrian and post-Cambrian marine ecosystems, documenting c...
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... This is relevant, as food competition and interactions with conspecifics have been predicted as drivers of social cognition (Schwartz et al. 2023;Tomasello 2023). However, indications of metacognition (deception and sexual mimicry) have been observed in cephalopods that are largely asocial (Schnell et al. 2021), so engaging with conspecifics may not be required for the evolution of metacognition. There are also other benefits to metacognition not considered here such as the rational allocation of limited memory resources (Russek et al. 2024) or greater behavioural flexibility as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. ...
Metacognition (awareness of one’s own knowledge) is taken for granted in humans, but its evolution in non-human animals is not well understood. While there is experimental evidence of seemingly metacognitive judgements across species, studies rarely focus on why metacognition may have evolved. To address this, I present an evolutionary model of the opt-out paradigm, a common experiment used to assess animal’s metacognition. Individuals are repeatedly presented with a task or problem and must decide between opting-out and receiving a fixed payoff or opting-in and receiving a larger reward if they successfully solve the task. Two evolving traits – bias and metacognition – jointly determine whether individuals opt-in. The task’s reward, the mean probability of success and the variability in success across trials, and the cost of metacognition were varied. Results identify two scenarios where metacognition evolves: (1) environments where success variability is high; and (2) environments where mean success is low, but rewards are high. Overall, the results support predictions implicating uncertainty in the evolution of metacognition but suggest metacognition may also evolve in conditions where metacognition can be used to identify cases where an otherwise inaccessible high payoff is easy to acquire.
... Cuttlefish are highly motivated by food rewards, show future-oriented decision-making (Billard et al., 2020;Schnell et al., 2021b), and have excellent visual-spatial cognitive skills (Scatà et al., 2016), including episodic-like memories (Jozet-Alves et al., 2013), indicating that they would be able to quickly learn the contingencies in non-instrumental tasks. The lineage to which cuttlefish belong, the coleoid cephalopod molluscs, diverged from vertebrates 500 million years ago, and likely independently evolved sophisticated cognition under different socioecological conditions to traditional vertebrate models (Amodio et al., 2019;Schnell et al., 2021a). The discovery of a drive for advanced non-instrumental information in this species would clarify whether this trait has evolved independently more than once, and would suggest that the underlying mechanisms are adaptive, important components of sophisticated cognition. ...
Humans and other animals often seek instrumental information to strategically improve their decisions in the present. Our curiosity also leads us to acquire non-instrumental information that is not immediately useful but can be encoded in memory and stored for use in the future by means of episodic recall. Despite its adaptive benefits and central role in human cognition, questions remain about the cognitive mechanisms and evolutionary origins that underpin curiosity. Here, we comparatively review recent empirical studies that some authors have suggested reflects curiosity in nonhuman animals. We focus on findings from laboratory tasks in which individuals can choose to gain advanced information about uncertain future outcomes, even though the information cannot be used to increase future rewards and is often costly. We explore the prevalence of preferences in these tasks across animals, discuss the theoretical advances that they have promoted, and outline some limitations in contemporary research. We also discuss several features of human curiosity that can guide future empirical research aimed at characterising and understanding curiosity in animals. Though the prevalence of curiosity in animals is actively debated, we surmise that investigating behavioural candidates for curiosity-motivated behaviour in a broader range of species and contexts, should help promote theoretical advances in our understanding of cognitive principles and evolutionary pressures that support curiosity-driven behaviour.
... During the last 50 years, there has been a 416% increase in cephalopod wildcaught fisheries landings, which reached a peak of 4 million tonnes in 2013 (Ospina-Alvarez et al. 2022). While many as causal reasoning, imagination, and mental attribution (Schnell et al. 2021). Octopuses also exhibit introspection, a cognitive process used to evaluate consciousness (Mather and Andrade 2023); this process involves internally evaluating sensory input and making decisions before taking action. ...
An understanding of octopus behaviour and their capture by fishing gears is required to inform efficient, sustainable, and ethical octopus fisheries. Here, the behaviour of Octopus tetricus was assessed in response to different bait and trap combinations in an outdoor mesocosm experiment. Eight wild octopuses were collected, maintained in individual tanks with flow-through seawater and aeration, and monitored with a 24-h video surveillance system. Six different traps and four different baits were presented to each octopus in various combinations during four sequential trials. Fine-mesh crab traps were the most successful in capturing octopus, accounting for 23 of the total 30 captures across all trials. Whereas solid trigger traps produced the greatest number of other interactions (e.g., octopus sitting on trap/in the entrance), averaging 43 interactions per trial, but were rarely triggered. Bait type did not influence octopus capture, trap interaction frequency, or octopus activity; however, only artificial bait types were trialled, and fresh natural baits may elicit a stronger response and should be investigated in future research. Generally, octopus were inactive, dedicating only 9.5% of their total time to active behaviours. Octopus activity varied with time of day, with peak activity during morning daylight (0800–1200) and the lowest activity during the dark hours of the very early morning (0000–0400). Additionally, capture numbers, trap interactions, and activity varied among individuals, with bolder personalities in some octopus. This natural variation among individual octopuses may lead to fishery-induced selection associated with the elevated capture frequency of bold or more active individuals.
... That is, we typically ascertain why a trait evolved partly by studying which species have it and which species do not, and how their natural histories otherwise compare. Indeed, Clayton and colleagues have powerfully advocated for the role of comparative analysis of which species express episodic memory as a key tool in uncovering its evolutionary history (Clayton & Krebs, 1994;Schnell, et al., 2021a;Van Horik et al., 2012). This seems to imply a puzzling circle: we need to know episodic memory's function to systematically search for it and establish its distribution, but we need to know its distribution to establish its function. ...
... Such physiological facts have been used to support divergent views about how ancient episodic memory itself is, given differing views of exactly which other neural structures are required, from claims that episodic memory is ancient (Allen & Fortin, 2013), to the view that is unique to primates or even humans (Murray et al., 2017), to the view that it has evolved convergently in different lineages (Zacks et al., 2022). Indeed, some behavioural evidence suggests episodic memory may be present in cuttlefish, which lack a hippocampus (Jozet-Alves et al., 2013;Schnell et al., 2021aSchnell et al., , 2021b. ...
... This line of investigation inspired a wide range of studies on many non-avian species, looking for what-where-when memory in food caching and other contexts, including (but not limited to) rodents such as rats, where both positive and negative results were found (Bird et al., 2003;Zhou & Crystal, 2009); Yucatan minipigs (Kouwenberg et al., 2009); dogs (Kaminski et al., 2008); zebrafish (Hamilton et al., 2016); and even cuttlefish (Billard et al., 2020;Jozet-Alves et al., 2013;Schnell et al., 2021aSchnell et al., , 2021b) -although it should be noted that details of the experimental paradigm, and hence its interpretability, vary across species. Two recent developments stand out, however. ...
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.
... In the case of gastropods, studies have been carried out with snails and slugs on classical conditioning ( Rivi et al. 2021), non-associative learning (Wells & Wells 1971;Willows 1973) and navigation (Wyeth 2019). As of cephalopods, studies reveal amazing cognitive abilities (for recent reviews see Amodio et al. 2019 andSchnell et al. 2021). There are demonstrations of classical and instrumental conditioning (Crancher et al. 1972;Papini & Bitterman 1991;Sanders 1975), habituation (Wells & Wells 1956), sensitization (Crook et al. 2011), spatial learning (Alves et al. 2008), imitation and social cognition (Amodio & Fiorito 2013;Fiorito & Scotto 1992), categorization (Boal 1991;Sanders 1975 As it has been already mentioned, the study of the intelligence of mollusks has been fruitful. ...
... Lukowiak and Dalesman, 2013;Mozzachiodi et al., 2013;Rivi et al., 2021), non-associative learning (Wells and Wells, 1971;Willows, 1973), and navigation (Wyeth, 2019). As for cephalopods, studies reveal amazing cognitive abilities (for recent reviews see Amodio et al., 2019 andSchnell et al., 2021). There are demonstrations of classical and instrumental conditioning (Crancher et al., 1972;Papini and Bitterman, 1991;Sanders, 1975), habituation (Wells and Wells, 1956), sensitization (Crook et al., 2011), spatial learning (Alves et al., 2007), imitation and social cognition (Amodio and Fiorito, 2013;Fiorito and Scotto, 1992), categorization (Boal, 1991;Sanders, 1975), tool use and problem solving (Fiorito et al., 1990;Mather and Dickel, 2017), play (Mather and Anderson, 1999), object permanence (Sanders and Young, 1940), episodic memory (Jozet- Alves et al., 2013), and communication (Lin et al., 2017). ...
A first approximation to the study of learning processes in bivalves is presented. A habituation procedure was developed using the slimy clam Ruditapes decussatus. The percentage of siphon withdrawal when they were exposed to a white light was measured. In Experiment 1, a habituation-discrimination procedure was used to study the stimulus intensity effect (350-lm vs 806 lm). Clams exposed to 350-lm showed a faster habituation than those exposed to 806-lm. Experiment 2 studied the effect of stimulus and intertrial interval (ITI) duration using a 2×2 design. Trials lasted 20 or 180 seconds, and the ITI lasted 5 or 10 minutes. A combined effect of these two parameters was obtained. Habituation was faster in clams exposed to 180-sec trials with a 5-min ITI. Finally, in Experiment 3 clams were trained with five blocks of five trials with a 5-min ITI. Groups differed on trial duration (20 or 180 secs.). The results showed a general spontaneous recovery effect that was more pronounced for the 180 secs. group. Also, it was found in this experimental condition a reduced response 24 hours after finishing training (long-term habituation). Altogether, this series of experiments constitutes a first systematic demonstration of habituation in bivalves.
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... With the probable and singular exception of cephalopods (Schnell et al., 2021), intelligent behaviours (discussed below) are associated with endothermy. While, generally assumed that endothermy is confined to Birds and Mammals, there are multiple incidences of endothermy in vertebrates and invertebrates (Legendre and Davesne, 2020;Wiemann et al., 2022). ...
... The Cephalopods are likely intelligent and ectothermic (Schnell et al., 2021). Able to perform complex problem solving and simple tool-use, at face-value, cephalopods would refute our suggestion that intelligence requires endothermy. ...
... These are: tool-use, which we redefine as "industry"; and language, written, spoken or otherwise expressed, as "abstraction". Tool-use as industry, then includes the Primates (Morgan et al., 2015), Cephalopods (Schnell et al., 2021), Corvids (Rutz et a., 2016) and some insects (Maák et al., 2016;Soley and Herberstein, 2023). There are probably other species engaging in tool-use, of which we are unaware. ...
Bayesian models have been used to infer the prevalence of life and intelligence elsewhere in the universe for several decades. In most, the emergence of intelligent life is judged against the time it took to emerge following the emergence of life as whole. However, such approaches are flawed in that they do not relate the emergence of “intelligent traits” to the absolute requirement for high rates of metabolism to support high levels of cognitive activity. They also make temporal assumptions that are based on fossil evidence, which is incomplete, particularly when one goes back to the Archaean. Instead, we provide a series of analyses, using simple Bayesian modelling to investigate the probability of two processes arising on Earth: endothermy and intelligent behaviours, the latter referred to as abstraction. The emergence of these traits is judged against known prior events, such as the origin of life (OoL); the Great Oxidation Event (GOE) and the Neoproterozoic Oxygenation Event (NOE). Likewise, we evaluate different plausible requirements for the emergence of abstract behaviours. The models show that there is a marginal preference for the requirement of oxygenation at the NOE over other events for the evolution of endothermy. However, such models are not fully able to distinguish preferences for the emergence of abstract behaviours. Finally, using the same approaches, we show that the emergence of Apes from other Primate lineages has a lower than expected probability.
... ;https://doi.org/10.1101https://doi.org/10. /2024 organisms are famous for their morphologically complex nervous systems (Styfhals et al. 2022) and their remarkable intellectual and behavioral repertoires (Amodio et al. 2019;Gutnick et al. 2023;Schnell et al. 2021). This is also the only known instance of a pulse of miRNA innovation within the non-vertebrates after the divergence of bilaterians from eumetazoans (Supp. ...
A prevailing problem in evolutionary biology is elucidating the genotype-phenotype map that characterizes how genomic activities regulate different aspects of organismal morphology and their variability in both space and time. Here, we explore potential causality between genome content and both morphological complexity and disparity by compiling the regulatory components (i.e., transcription factors, RNA binding proteins, and microRNA families) as well as a representative set of non-regulatory housekeeping genes in 32 species belonging to a wide variety of animal phyla, altogether encapsulating a number of varying genomic characteristics and morphological diversities. A principal component analysis of these four non-overlapping genomic components from each of these 32 species in relation to their last common ancestor revealed that no relationship exists between genome space and disparity, as changes to animal body plans appear to be largely the result of changes to the gene regulatory networks that govern animal development rather than gaining or losing specific sets of regulatory genes. However, using both phylogenetically correlated as well as phylogenetically uncorrelated statistical tests, we find a strong relationship between the loss of all considered gene types and the advent of some parasitic taxa, as well as between microRNA innovations and organismal complexity. While this analysis of genomic features suggests how complexity and disparity are each encoded in the genome, further analysis of the regulatory networks in which they participate should provide a more comprehensive description of how organisms diversify their morphologies over time through alterations in their genomic components.
... Nevertheless, if solving is ancestral and conserved as reactive functions or active behaviors, then transitions from B1 to B2 intelligence and from B2 to humans (see Table 1 legend for categories) would have implicated the emergence of augmented or novel solving abilities and planning capacities. For example, some cognitive adaptations in birds, mammals and cephalopods involve the development of brain regions permitting more acute perception, reaction to movement and anticipation of near future events [88]; [132]. Disentangling the selective drivers of the evolution of generic ability will be a daunting challenge. ...
I develop a framework -- the Theory of Intelligences -- that applies across all systems from physics, to biology, humans and AI. Intelligence can be expressed in informational units or in units relative to goal difficulty, the latter defined as goal complexity relative to system ability. I present general equations for intelligence and a simple expression for the evolution of intelligence traits. The measures presented could be the basis for further refinements to gauge different facets of intelligence for any stepwise transformation of information.
... Octopuses exhibit behavioural exibility and many attributes suggestive of high intelligence. Although these attributes alone are insu cient evidence of complex cognition (Emery and Clayton 2004; Amodio 2019), they are considered precursors for many associated capacities, such as causal reasoning, imagination, and mental attribution (Schnell et al. 2021). Octopuses also exhibit introspection, a cognitive process used to evaluate consciousness (Mather and Andrade 2023); this process involves internally evaluating sensory input and making decisions before taking action. ...
Octopus fisheries are expanding globally. However, given their complex behavioural repertoires, cognitive capacities and individual personalities among octopuses, careful consideration of their interactions with and capture by fishing gears is required to inform efficient, sustainable, and ethical fisheries development. Here, the behaviour of Octopus tetricus was assessed in response to different bait and trap combinations in an outdoor mesocosm experiment. Eight wild octopuses were collected, maintained in individual tanks with flow-through seawater and aeration, and monitored with a 24-h video surveillance system. Six different trap types and four different baits were presented to each octopus in various combinations during four sequential trials. Fine-mesh crab traps were the most successful in capturing octopus, accounting for 23 of the total 30 captures across all trials. Whereas solid trigger traps produced the greatest number of other interactions (e.g., octopus sitting on trap or in the entrance), averaging 43 interactions per trial, but were rarely triggered. Bait type did not influence octopus capture, trap interaction frequency, or octopus activity. Octopus were generally inactive, dedicating only 9.5% of their total time to active behaviours. Octopus activity varied with time of day, with peak activity during morning daylight (0800–1200) and the lowest activity during the dark hours of the very early morning (0000–0400). Additionally, capture numbers, trap interactions, and activity varied among individuals, with bolder personalities in some octopus. This natural variation among individual octopuses may lead to fishery-induced selection associated with the elevated capture frequency of bold or more active individuals.
