Domestic dogs: Born human whisperers

Vignieri does a summary of recent work by  Bray et al. and Salomans et al. in Current Biology

 

The closest relative to dogs, “man’s best friend,” is the wolf, a wily predator that generally avoids human interaction. For decades, researchers and dog owners have wondered how the leap to domestication occurred. The main hypothesis invoked very early selection for wolves that “liked”—or least tolerated—humans, and the connection strengthened from there. However, there is still some debate about whether the degree to which dogs interact and communicate with humans is a learned trait. Two recent studies appear to close the book on this learning hypothesis. Bray et al. looked at about 400 puppies and found that at this young age and without much human interaction, they were adept at following human gestures and positively responded to high-pitched “puppy talk.” Further, there was variation in these responses with an association between relatedness and social communication skills, which supports a genetic driver. Salomons et al. compared dog and wolf puppies and found no difference in general cognitive responses, but much greater responsiveness to human gestures and eye contact, in dog puppies. Importantly, this happened even though the dog pups had received less actual human interaction than did the wolf pups. These studies confirm that dogs’ interest in communication with humans is an evolved trait unique to their lineage.

The 31st First Annual Ig Nobel Ceremony -

I pass on this Science.org summary of the virtual awards ceremony.

Musical cats, upside-down rhinos, and submarine cockroaches took the gold last night at the 31stst annual Ig Nobel Prize ceremony—an awards show honoring research that “makes people laugh, then think.” Although the pandemic kept the ceremony virtual for a second year, organizers made the best of the format. Nobel laureates, including Frances Arnold (chemistry, 2018) and Eric Maskin (economics, 2007), “handed” awardees their prizes—self-assembled 3D paper gears printed with pictures of teeth. This year’s theme was “engineering.”

The biology prize—one of 10 awards—went to a series of studies on the purrs, trills, tweedles, murmurs, meows, yowls, and other sounds cats seem to use to communicate their desires to humans. Cat vocalization researcher Susanne Schötz at Lund University has been hard at work cracking the “cat code” with her collaborators since 2011, handing the microphone to cats to analyze what felines mean when they meow.

Schötz was honored for several papers, including one on how well humans interpret cat “meowsic.” She reported that when cats want food from their owners, their sounds tend to rise in pitch at the end. If the cats are anxious about a trip to the vet, however, they drop their pitch. When she played meows for a group of 30 humans, she found they guessed the cats’ feelings from intonation alone the majority of the time. Cat owners were the best guessers, showing that when it comes to cats, practice makes purrfect.

Other prizes went to research on animals that reached for the sky and dove under the sea. The transportation prize honored researchers who determined that the best way to transport a rhinoceros by helicopter is upside down. This technique has been vital to conservationists who move large animals such as rhinos and elephants to keep them safe from poachers or maintain genetic diversity. During the ceremony, the honorees assured Nobel laureate Richard Roberts (physiology or medicine, 1993) that they’d tested the technique on themselves before trying it on rhinos. Roberts maintained that if he ever had to be transported to a safer place, “I hope not to be doing it upside down.”

The entomology prize highlighted one of the most fraught human-animal relationships: the ongoing battle between humans and cockroaches. For this prize, the awards committee dug deep into the archives for a study from 1971 titled, “A new method of cockroach control on submarines.” Retired U.S. Navy Cmdr. John Mulrennan Jr. accepted the award for developing a new technique for getting rid of cockroaches on navy submarines using a pesticide called dichlorvos after the ethylene oxide gas previously used made someone sick. “The Navy was happy at the time,” he noted in his acceptance speech, although he doesn’t know whether it still uses his technique.

Other awards included the physics prize, for an analysis of why people in crowds don’t constantly run into each other, and the kinetics prize, for a study answering why they sometimes do (the answer: cellphones). The ecology prize went to an analysis of bacteria that hitch a ride on used chewing gum, the peace prize went to a test of how effectively beards protect faces from punches (they soften the blow), and the medicine prize went to a study of whether orgasms can serve as an effective nasal decongestant. (They can, but the effects only last about 1 hour.) Winners also received a fake 10 trillion Zimbabwean dollar bill from Marc Abrahams, editor of the Annals of Improbable Research and host of the ceremony.

Dispersed throughout the night were several “24/7” talks, in which researchers gave full technical descriptions of a scientific topic in 24 seconds followed by a simple explanation in seven words. (“Coffee drinking: good, good for you … maybe!”) To round out the proceedings, scientists and opera singers performed an original three-act miniopera called A Bridge Between People. Its plot revolved around children bringing together angry adults by building tiny suspension bridges between them.

Abrahams ended the night by expressing his hope that everyone could be together in person next year, and by delivering his traditional signoff: “If you didn’t win an Ig Nobel Prize tonight—and especially if you did—better luck next year.”

Babbling bats

An interesting piece from Fernandez et al.:

Babbling is a production milestone in infant speech development. Evidence for babbling in nonhuman mammals is scarce, which has prevented cross-species comparisons. In this study, we investigated the conspicuous babbling behavior of Saccopteryx bilineata, a bat capable of vocal production learning. We analyzed the babbling of 20 bat pups in the field during their 3-month ontogeny and compared its features to those that characterize babbling in human infants. Our findings demonstrate that babbling in bat pups is characterized by the same eight features as babbling in human infants, including the conspicuous features reduplication and rhythmicity. These parallels in vocal ontogeny between two mammalian species offer future possibilities for comparison of cognitive and neuromolecular mechanisms and adaptive functions of babbling in bats and humans.

Watching a brain encode present, past, and future….

We all exist as an ongoing simulation of past, present, and future in our brains, with the hallucination we take to be reality being perturbed only when our brains’ expectations are not met. Dotson and Yartsev do experiments in flying bats (of a sort not permitted in humans) that record from the hippocampus showing patterns of neuron activity of the sort needed to support this process. They find that this activity not only encodes the bat’s present location but also signals its positions in the past and future. The technology involved in doing the brain implants that record and wirelessly transmit the neuronal activity, as well as the sophisticated data analysis, is truly awesome (One has to download a massive technical supplement, much too large to include in the article, to get the details.) Here I pass on only the editor’s summary and the abstract for the article:  

Representing space in past and future

As an organism moves through space, its brain has to remember its most recent location and anticipate its future position, not just its current place in the world. Earlier studies reported so-called retrospective and prospective place coding in rats while they were running along linear tracks. However, it would be advantageous to study an animal that rapidly moves through three-dimensional space with high precision. Dotson and Yartsev recorded from flying bats to investigate whether place cell activity in hippocampus area CA1 represents local (current) or nonlocal positions. They discovered that the hippocampus not only encodes the bat's present location but also signals its positions in the past and future.

Abstract

Navigation occurs through a continuum of space and time. The hippocampus is known to encode the immediate position of moving animals. However, active navigation, especially at high speeds, may require representing navigational information beyond the present moment. Using wireless electrophysiological recordings in freely flying bats, we demonstrate that neural activity in area CA1 predominantly encodes nonlocal spatial information up to meters away from the bat’s present position. This spatiotemporal representation extends both forward and backward in time, with an emphasis on future locations, and is found during both random exploration and goal-directed navigation. The representation of position thus extends along a continuum, with each moment containing information about past, present, and future, and may provide a key mechanism for navigating along self-selected and remembered paths.

Evidence that monkeys have conscious awareness of self - they know what they saw.

Ben-Haim et al. Disentangle perceptual awareness from nonconscious processing in rhesus monkeys  

Significance

Many animals perform complex intelligent behaviors, but the question of whether animals are aware while doing so remains a long debated but unanswered question. Here, we develop a new approach to assess whether nonhuman animals have awareness by utilizing a well-known double dissociation of visual awareness—cases in which people behave in completely opposite ways when stimuli are processed consciously versus nonconsciously. Using this method, we found that a nonhuman species—the rhesus monkey—exhibits the very same behavioral signature of both nonconscious and conscious processing. This opposite double dissociation of awareness firstly allows stripping away the long inherent ambiguity when interpreting the processes governing animal behavior. Collectively, it provides robust support for two distinct awareness modes in nonhuman animals.

Abstract

Scholars have long debated whether animals, which display impressive intelligent behaviors, are consciously aware or not. Yet, because many complex human behaviors and high-level functions can be performed without conscious awareness, it was long considered impossible to untangle whether animals are aware or just conditionally or nonconsciously behaving. Here, we developed an empirical approach to address this question. We harnessed a well-established cross-over double dissociation between nonconscious and conscious processing, in which people perform in completely opposite ways when they are aware of stimuli versus when they are not. To date, no one has explored if similar performance dissociations exist in a nonhuman species. In a series of seven experiments, we first established these signatures in humans using both known and newly developed nonverbal double-dissociation tasks and then identified similar signatures in rhesus monkeys (Macaca mulatta). These results provide robust evidence for two distinct modes of processing in nonhuman primates. This empirical approach makes it feasible to disentangle conscious visual awareness from nonconscious processing in nonhuman species; hence, it can be used to strip away ambiguity when exploring the processes governing intelligent behavior across the animal kingdom. Taken together, these results strongly support the existence of both nonconscious processing as well as functional human-like visual awareness in nonhuman animals.

(Note: Establishing double dissociation of awareness used a nonverbal spatial-cueing paradigm. Motivated readers can email me to obtain a PDF of the article which describes this paradigm.)

Sensitivity to geometric shape: A putative signature of human singularity

From Sablé-Meyer et al.:

Among primates, humans are special in their ability to create and manipulate highly elaborate structures of language, mathematics, and music. Here we show that this sensitivity to abstract structure is already present in a much simpler domain: the visual perception of regular geometric shapes such as squares, rectangles, and parallelograms. We asked human subjects to detect an intruder shape among six quadrilaterals. Although the intruder was always defined by an identical amount of displacement of a single vertex, the results revealed a geometric regularity effect: detection was considerably easier when either the base shape or the intruder was a regular figure comprising right angles, parallelism, or symmetry rather than a more irregular shape. This effect was replicated in several tasks and in all human populations tested, including uneducated Himba adults and French kindergartners. Baboons, however, showed no such geometric regularity effect, even after extensive training. Baboon behavior was captured by convolutional neural networks (CNNs), but neither CNNs nor a variational autoencoder captured the human geometric regularity effect. However, a symbolic model, based on exact properties of Euclidean geometry, closely fitted human behavior. Our results indicate that the human propensity for symbolic abstraction permeates even elementary shape perception. They suggest a putative signature of human singularity and provide a challenge for nonsymbolic models of human shape perception.

Sexiest birds on the planet - Manakins have the best moves

Elizabeth Pennisi describes reports from a recent virtual meeting of the Society for Integrative and Comparative Biology on the genetic underpinnings of the elaborate plumage and dance displays of Ecuador's club winged manakin, products of sexual selection:

For a glimpse of the power of sexual selection, the dance of the golden-collared manakin is hard to beat. They court with their flashy plumage, loud wing clapping, and acrobatic leaps and twists to gain the fussy female's favor. (As biologists have understood since Charles Darwin, such exhibitionism evolves when females choose to mate with males that have the most extravagant appearances and displays—a proxy for fitness.) Now, by studying the genomes of the golden-collared manakin (Manacus vitellinus) and its relatives, researchers are exploring the genes that drive these elaborate behaviors and traits. With four manakin genomes, and two already published, researchers are now able to describe the genetic underpinnings behind some of the birds' displays. In addition, by mapping traits and genes onto the manakin family tree, researchers are beginning to trace the stepwise genetic changes that led to the most elaborate displays and determine whether sexual selection works differently from natural selection.

So...whatcha gonna offer me for this cell phone I stole from you?

Macaque monkeys have learned how to drive a hard bargain.They have learned to barter for food with humans to return stolen possessions according to how highly an object is valued. Here is a brief description by Vignieri of work by Leca et al.:

The use of tokens as a bartering tool in nonhuman primate studies has taught us much about the willingness of nonhuman primates to engage in economic transactions. The question of whether it reflects a phenomenon that might emerge in natural conditions has received less attention. Long-tailed macaques (Macaca fascicularis) living in a Balinese temple regularly steal visitors' possessions and then barter for food with humans anxious to regain their belongings. Leca et al. discovered that they preferentially steal items of high value (for example, digital devices and wallets) over those with low value (for example, empty bags or hairpins) because higher-value food rewards tend to be offered for items that humans value more. The ability to identify high-value objects increases with age and experience, as does the macaques' skill as thieves. The animals in this group have been stealing and trading for more than 30 years, suggesting that the practice is culturally transmitted.

Why cats like catnip...

Interesting work from Uenoyama et al.:

Domestic cats and other felids rub their faces and heads against catnip (Nepeta cataria) and silver vine (Actinidia polygama) and roll on the ground as a characteristic response. While this response is well known, its biological function and underlying mechanism remain undetermined. Here, we uncover the neurophysiological mechanism and functional outcome of this feline response. We found that the iridoid nepetalactol is the major component of silver vine that elicits this potent response in cats and other felids. Nepetalactol increased plasma β-endorphin levels in cats, while pharmacological inhibition of μ-opioid receptors suppressed the classic rubbing response. Rubbing behavior transfers nepetalactol onto the faces and heads of respondents where it repels the mosquito, Aedes albopictus. Thus, self-anointing behavior helps to protect cats against mosquito bites. The characteristic response of cats to nepetalactol via the μ-opioid system provides an important example of chemical pest defense using plant metabolites in nonhuman mammals.

How mice feel each other's pain or fear

The abstract from Smith et al, who show the brain basis of empathetic behaviors in mice that mirror those in humans:

Empathy is an essential component of social communication that involves experiencing others’ sensory and emotional states. We observed that a brief social interaction with a mouse experiencing pain or morphine analgesia resulted in the transfer of these experiences to its social partner. Optogenetic manipulations demonstrated that the anterior cingulate cortex (ACC) and its projections to the nucleus accumbens (NAc) were selectively involved in the social transfer of both pain and analgesia. By contrast, the ACC→NAc circuit was not necessary for the social transfer of fear, which instead depended on ACC projections to the basolateral amygdala. These findings reveal that the ACC, a brain area strongly implicated in human empathic responses, mediates distinct forms of empathy in mice by influencing different downstream targets. 

Here is a summary graphic from a perspective by Klein and Gogolla (click to enlarge):

Cuttlefish can pass the marshmellow test.

Cephalopod mullusks like octopuses or cuttlefishes show remarkable intelligence. My most engaged and soothing viewing experience during the pandemis has been watching "My Octopus Teacher" on Netflix. Now recent work pointed to by Greenwood shows that cuttlefish can pass the famous marshmellow test, forgoing immediate gratification if experience has shown that waiting produces a larger reward:

Decision-making, when humans and other animals choose between two options, is not always based on the absolute values of the options but can also depend on their relative values. The present study examines whether decision-making by cuttlefish is dependent on relative values learned from previous experience. Cuttlefish preferred a larger quantity when making a choice between one or two shrimps (1 versus 2) during a two-alternative forced choice. However, after cuttlefish were primed under conditions where they were given a small reward for choosing one shrimp in a no shrimp versus one shrimp test (0 versus 1) six times in a row, they chose one shrimp significantly more frequently in the 1 versus 2 test. This reversed preference for a smaller quantity was not due to satiation at the time of decision-making, as cuttlefish fed a small shrimp six times without any choice test prior to the experiment still preferred two shrimps significantly more often in a subsequent 1 versus 2 test. This suggests that the preference of one shrimp in the quantity comparison test occurs via a process of learned valuation. Foraging preference in cuttlefish thus depends on the relative value of previous prey choices.

Nature's lessons for a more kind society.

I recently came across this 2009 MindBlog post... relevant to our times. Here is a re-post (this link to the original post takes you to some comments.)

Blog reader Gary Olson has pointed me to his review of Franz De Waal's new book "The Age of Empathy: Nature’s Lessons For A Kinder Society." From that review:

de Waal provides compelling support for the proposition that humans are “preprogrammed to reach out.” From dolphins ferrying injured companions to safety and grieving elephants, baboons and cats (yes, even cats) to commiserating mice and hydrophobic chimps risking death to save a drowning companion, this is a major contribution to understanding the biological genesis of our inborn capacity for empathy, hence morality. In seven crisply written and wholly accessible chapters de Waal methodically demolishes the rationale behind Gordon Gekko’s admonition in the film "Wall Street" that greed “captures the essence of the evolutionary spirit.”...De Waal objects to an unrestrained market system, not capitalism itself. He prefers that the economic system be mitigated by more attention to empathy in order to soften its rough edges...Nevertheless, de Waal seriously underestimates certain capitalist imperatives and the role played by elites in cultivating callousness, thereby undermining social solidarity, reciprocity and empathy. Capitalist culture devalues an empathic disposition, and, as Erich Fromm argued some fifty years ago, there is a basic incompatibility between the underlying principles of capitalism and the lived expression of an ethos of empathy.

Kitty see, kitty do: cat imitates human

I am immediately going to start trying this with my abyssinians! Cats have been notoriously hard to study, and this study reinforces, for example, that cats 0 unlike dogs - are likely to show their true abilities only if their owner is present.   See the description by David Grimm. 

Which way are you wagging your tail?

Blakeslee writes a review (PDF here) of work by Vallortigara et al (PDF here) on emotional asymmetric tail wagging by dogs that is a further reflection of lateralized functions of the brain. Some edited clips from her article:

In most animals, including birds, fish and frogs, the left brain specializes in behaviors involving what the scientists call approach and energy enrichment. In humans, that means the left brain is associated with positive feelings, like love, a sense of attachment, a feeling of safety and calm. It is also associated with physiological markers, like a slow heart rate.

At a fundamental level, the right brain specializes in behaviors involving withdrawal and energy expenditure. In humans, these behaviors, like fleeing, are associated with feelings like fear and depression. Physiological signals include a rapid heart rate and the shutdown of the digestive system.

Because the left brain controls the right side of the body and the right brain controls the left side of the body, such asymmetries are usually manifest in opposite sides of the body. Thus many birds seek food with their right eye (left brain/nourishment) and watch for predators with their left eye (right brain/danger).

In humans, the muscles on the right side of the face tend to reflect happiness (left brain) whereas muscles on the left side of the face reflect unhappiness (right brain).

Dog tails are interesting...because they are in the midline of the dog’s body, neither left nor right. So do they show emotional asymmetry, or not?

Vallortigara et al show that when dogs were attracted to something, including a benign, approachable cat, their tails wagged right, and when they were fearful, their tails went left. It suggests that the muscles in the right side of the tail reflect positive emotions while the muscles in the left side express negative ones.

Brain asymmetry for approach and withdrawal seems to be an ancient trait..Thus it must confer some sort of survival advantage on organisms.

Animals that can do two important things at the same time, like eat and watch for predators, might be better off. And animals with two brain hemispheres could avoid duplication of function, making maximal use of neural tissue.

The asymmetry may also arise from how major nerves in the body connect up to the brain... Nerves that carry information from the skin, heart, liver, lungs and other internal organs are inherently asymmetrical, he said. Thus information from the body that prompts an animal to slow down, eat, relax and restore itself is biased toward the left brain. Information from the body that tells an animal to run, fight, breathe faster and look out for danger is biased toward the right brain.

(This is a re-posting of the MindBlog post of 4/27/2007, material as interesting and fresh today as it was then.)

Winner of Dance your PhD 2019 contest - Social experiences in larval zebrafish and their brains

The videos of several of the contestants can be see at this link, where you will also find a description of the work and people behind the winner, a very creative visual treat, shown here:

How human breeding has changed dogs’ brains

Hecht et al. have identified brain networks in dogs related to behavioral specializations roughly corresponding to sight hunting, scent hunting, guarding, and companionship. Here is their detailed abstract:

Humans have bred different lineages of domestic dogs for different tasks such as hunting, herding, guarding, or companionship. These behavioral differences must be the result of underlying neural differences, but surprisingly, this topic has gone largely unexplored. The current study examined whether and how selective breeding by humans has altered the gross organization of the brain in dogs. We assessed regional volumetric variation in MRI studies of 62 male and female dogs of 33 breeds. Neuroanatomical variation is plainly visible across breeds. This variation is distributed nonrandomly across the brain. A whole-brain, data-driven independent components analysis established that specific regional subnetworks covary significantly with each other. Variation in these networks is not simply the result of variation in total brain size, total body size, or skull shape. Furthermore, the anatomy of these networks correlates significantly with different behavioral specialization(s) such as sight hunting, scent hunting, guarding, and companionship. Importantly, a phylogenetic analysis revealed that most change has occurred in the terminal branches of the dog phylogenetic tree, indicating strong, recent selection in individual breeds. Together, these results establish that brain anatomy varies significantly in dogs, likely due to human-applied selection for behavior.

Facial muscles in dogs evolved for interactions with humans.

From Kaminski et al. (check out the videos in the article):

Domestication shaped wolves into dogs and transformed both their behavior and their anatomy. Here we show that, in only 33,000 y, domestication transformed the facial muscle anatomy of dogs specifically for facial communication with humans. Based on dissections of dog and wolf heads, we show that the levator anguli oculi medialis, a muscle responsible for raising the inner eyebrow intensely, is uniformly present in dogs but not in wolves. Behavioral data, collected from dogs and wolves, show that dogs produce the eyebrow movement significantly more often and with higher intensity than wolves do, with highest-intensity movements produced exclusively by dogs. Interestingly, this movement increases paedomorphism and resembles an expression that humans produce when sad, so its production in dogs may trigger a nurturing response in humans. We hypothesize that dogs with expressive eyebrows had a selection advantage and that “puppy dog eyes” are the result of selection based on humans’ preferences.

Ready to pounce - Cat smarts get some attention

I live in a symbiotic relationship with my two Abyssinian cats, and so was gratified, given that canine social cognition is the subject of dozens of scientific papers, to see that feline cognition is beginning to get more attention. One simple reason for the difference is that dogs want to please humans and cooperate with experimenters, while cats could generally care less, and after a few trials will walk away from earnest efforts to engage their responses. When a human points at something, a chimp will not react, but a dog, like a human toddler, knows to look at the same thing. Turns out that cats do the same thing, they will trot over to a bowl that a human points to. It is turning out that cats match dogs in many tests of social smarts. Alas, I'm going to show you a cat video... not of some adorable feline faux pas, but of behavioral work being done with cats:



And, since I'm showing cat pictures, I can't resist introducing you to Abyssinians Marvin and Melvin, shown napping while I'm driving between Madison WI and Austin TX.

Impacts of outdoor artificial light on plant and animal species.

Gaston does a perspective article describing how the nighttime lighting up of our planet is profoundly disturbing the activities of many animal and plant species. I pass on three paragraphs:

Artificial light at night can usefully be thought of as having two linked components. The first component—direct emissions from outdoor lighting sources, which include streetlights, building and infrastructure lighting, and road vehicle headlamps—is spatially extremely heterogeneous. Ground-level illuminance in the immediate vicinity can vary from less than 10 lux (lx) to more than 100 lx (for context, a full moon on a clear night has an illuminance of up to 0.1 lx). It often declines rapidly over distances of a few meters. However, emissions from unshielded lights can, when unobstructed, carry horizontally over many kilometers, making artificial light at night both an urban and a rural issue.

The second component of artificial light at night is skyglow, the brightening of the nighttime sky caused mainly by upwardly emitted and reflected artificial light that is scattered in the atmosphere by water, dust, and gas molecules. Although absolute illuminance levels are at most about 0.2 to 0.5 lx, much lower than those from direct emissions, these are often sufficiently high to obscure the Milky Way, which is used for orientation by some organisms. In many urban areas, skyglow even obscures lunar light cycles, which are used by many organisms as cues for biological activity.

In the laboratory, organismal responses, such as suppression of melatonin levels and changes to behavioral activity patterns, generally increase with greater intensities of artificial light at night. It is challenging to establish the form of such functional relationships in the field, but experiments and observations have shown that commonplace levels of artificial light at night influence a wide range of biological phenomena across a wide diversity of taxa, including individual physiology and behavior, species abundances and distributions, community structure and dynamics, and ecosystem function and process. Exposure to even dim nighttime lighting (below 1 lx) can drastically change activity patterns of both naturally day-active and night-active species. These effects can be exacerbated by trophic interactions, such that the abundances of species whose activity is not directly altered may nonetheless be severely affected under low levels of nighttime lighting.

Giving Ecstasy to Octopuses

Edsinger and Dölen have found out how to make the normally shy and retiring octopus into a party animal. They found that MDMA (phenethylamine (+/−)-3,4-methylendioxymethamphetamine, also known as Ecstasy) has prosocial effects, just as it does in humans. The indicates that the role of the serotonergic neurotransmission (that MDMA acts on) in regulating social behaviors has been evolutionarily conserved over 500 million years.

Human and octopus lineages are separated by over 500 million years of evolution and show divergent anatomical patterns of brain organization. Despite these differences, growing evidence suggests that ancient neurotransmitter systems are shared across vertebrate and invertebrate species and in many cases enable overlapping functions. Sociality is widespread across the animal kingdom, with numerous examples in both invertebrate (e.g., bees, ants, termites, and shrimps) and vertebrate (e.g., fishes, birds, rodents, and primates) lineages [6]. Serotonin is an evolutionarily ancient molecule that has been implicated in regulating both invertebrate and vertebrate social behaviors, raising the possibility that this neurotransmitter’s prosocial functions may be conserved across evolution. Members of the order Octopoda are predominantly asocial and solitary. Although at this time it is unknown whether serotonergic signaling systems are functionally conserved in octopuses, ethological studies indicate that agonistic behaviors are suspended during mating, suggesting that neural mechanisms subserving social behaviors exist in octopuses but are suppressed outside the reproductive period. Here we provide evidence that, as in humans, the phenethylamine (+/−)-3,4-methylendioxymethamphetamine (MDMA) enhances acute prosocial behaviors in Octopus bimaculoides. This finding is paralleled by the evolutionary conservation of the serotonin transporter (SERT, encoded by the Slc6A4 gene) binding site of MDMA in the O. bimaculoides genome. Taken together, these data provide evidence that the neural mechanisms subserving social behaviors exist in O. bimaculoides and indicate that the role of serotonergic neurotransmission in regulating social behaviors is evolutionarily conserved.