The size of the reward matters too for learning speed

Amazing stuff!

"Scientists have long believed that training an animal, even to perform simple tasks, is a painstaking process requiring hundreds of repetitions. Under standard protocols, animals receive only a small reward after each attempt, maximizing the number of reinforcements per training session. Accumulated experience, at least according to conventional wisdom, is more important than the size of the incentive. New experiments in mice, however, may upend this long-held assumption.

“I mean this quite literally, no one ever checked,” neuroscientist Josh Dudman said in a statement. For the new study, his lab trained mice to complete a range of navigation, motor skill, and decision-making tasks. Thirsty mice that received a few large gulps of water as a reward, the team reported, became experts much faster than animals that got many tiny sips . ..."

"KEY TAKEAWAYS

• The Dudman Lab examined what happens when animals are given bigger-than-normal rewards as they learned to perform a task. They found that larger rewards speed up learning and reduce individual differences, even though animals had much less experience performing the task.
• The larger payout causes a sustained increase in dopamine — a chemical messenger in the brain that helps regulate learning and motivation. This allows the brain to gain more from each experience and be more engaged in the task at hand, both of which contribute to faster learning.
• The findings could change how scientists think about how brains learn, the role of dopamine in learning, and how they study learning.

..."

From the editor's summary and abstract:

"Editor’s summary

Training an animal on a complex task is often a painstaking, incremental process. This is because conventional behavioral learning protocols focus on minimizing reward to maximize trials. Gong et al. tested how reward size shapes learning in mice. Very large rewards markedly accelerated learning across tasks and led to increased dopamine release in the striatum.

Animals learned faster, became more efficient in reward collection, remained engaged in the tasks, and showed across-session improvements compared with smaller reward magnitudes.

Striatal dopamine responses scaled with reward size and extending dopamine activity using optogenetics reproduced many of the learning benefits. These results provide an important contribution to our understanding of the role of large rewards in learning and motivation. ...

Structured Abstract

INTRODUCTION

Across different disciplines that share an interest in learning, from artificial intelligence (AI) to experimental psychology, it has long been assumed that there is a free parameter, the learning rate, that determines individual variance in learning efficiency and is relatively independent of the magnitude of reward.

This suggests that learning depends primarily on the amount of experience (number of rewards). However, recent theoretical work mapping dopamine (DA) function onto reinforcement learning algorithms, combined with classic results on DA encoding of reward, suggested that learning rates might in fact depend upon reward magnitude. This also raises the possibility that, as a field, we may have settled on suboptimal reward magnitude distributions that slow training in complex laboratory tasks and also underestimated the efficiency of animal learning.

RATIONALE

An influential set of observations led to the hypothesis that DA neuron activity implements the reward prediction error component of reinforcement learning algorithms. However, recent work has proposed that DA activity may map onto the learning rate during acquisition.

The learning rate parameter, as the name implies, determines how fast learning converges to its asymptote. Classic experimental results demonstrated that DA activity is correlated with reward magnitude. Together, these two points imply an unexpected hypothesis:

Reward magnitude could determine the efficiency of reinforcement learning. There are few data on what magnitude of reward is optimal for learning in any laboratory animal. This is especially true for the range of navigation, motor skill, and decision-making tasks typical of modern systems neuroscience experiments in mice.

Nonetheless, essentially the entire field uses reward magnitudes from within a very small range. Those chosen reward magnitudes are quite small relative to the daily needs of a mouse (<1%). Thus, we set out to determine whether, and if so why, increases in reward magnitude could increase the efficiency of animal learning.

RESULTS

Increasing reward magnitude by one to two orders relative to the standard reward sizes used in the field substantially increased the efficiency of learning across a range of tasks. We found that mice could learn from at least an order of magnitude fewer trials in a hidden target navigation task, an effort-based reach-to-pull motor skill task, and a sensorimotor decision-making task.

In general, across all three tasks, the efficiency of learning was increased without a notable change in the quality of the final, trained performance. At the upper limit, these effects could be substantial. For example, some mice learned a hidden target navigation task in only a few experiences of reinforcement, something that requires hundreds or thousands of reinforcements using standard reward magnitudes. We further showed that these effects could be well explained once one appreciates that the efficiency of learning is determined by three critical components:

(i) the learning rate,

(ii) the ability to capture learned improvements from prior sessions, and

(iii) the extent of sustained engagement in a task.

In our study, large rewards improved all three aspects. Large rewards produced longer, more sustained activity of DA neurons during reward consumption. We tested whether augmenting normal responses to reward with optogenetic-mediated sustained activation of DA were sufficient to enhance learning efficiency with standard reward magnitudes. Sustained optogenetic “boosting” of DA reward responses was able to increase learning efficiency in both hidden target navigation and the effort-based motor skill task.

DA stimulation increased learning efficiency by increasing the learning rate and reducing disengagement, but failed to enhance capture of prior learning. Finally, we showed that increasing reward magnitude, while always improving learning as measured in DA activity, does not always lead to obvious improvements in behavioral measures of learning. For example, the presence of large rewards appears to interfere with anticipatory behavior in classical conditioning paradigms.

CONCLUSION

We found that larger reward magnitudes than used in the field could indeed enhance the learning efficiency of mice across a range of complex tasks, including navigation, motor skill, and decision-making. One of the largest sources of variance across individual mice was the ability to stay engaged in task performance. Unexpectedly, variance in learning rate across individuals appeared to be much smaller. As a result, large rewards could substantially attenuate variance across individuals in learning efficiency.

Finally, mesolimbic DA neuron activity could produce multiple effects on learning depending upon the magnitude and time course of DA activation."

ScienceAdviser

The Bigger the Reward, the Faster We Learn  (original news release) "Researchers in the Dudman Lab at HHMI’s Janelia Research Campus found that learning happens faster when there’s a bigger payoff for success, potentially changing how neuroscientists think about learning and how they study it"

Reward magnitude determines reinforcement learning efficiency (no public access)

New research from the Dudman Lab finds animals learn faster when they are given larger-than-normal rewards as they learn to perform a task. Artificially extending the dopamine signals associated with small rewards also caused learning to happen faster.

Territorial conflict with rival groups over food and mates may explain male primates’ large size, some male primates are up to twice the size of females

Amazing stuff!

"... Many species in the primate order — which includes monkeys, apes and lemurs — have sexual size dimorphism, meaning an average size difference between the sexes. While some primates like gibbons show barely any size disparity, others such as baboons and gorillas can have males that are twice as massive as the females. ...

“But primate groups are rarely isolated,” ... Neighboring groups commonly interact. They overlap in territory and compete for resources such as food and mates. ..."

"Sexual selection acting on males through intrasexual competition for mates is a well-established driver of sexual size dimorphism (SSD) in primates. However, studies typically focus on within-group competition, overlooking the potential significance of competition arising from interactions between neighbouring social groups, particularly when home ranges overlap.

Here, we analysed the relationships between SSD, mating system and different proxies of range use across up to 143 species of anthropoid and strepsirrhine primates.

Contrary to expectations, mating system—a commonly used proxy for male competition—did not significantly predict SSD.

Instead, male-biased SSD increased with home range overlap and encounter rate between social groups, even after accounting for mating system and body size allometry.

This suggests that spatial pressures, such as the latent threat of competition from rival groups, impose stronger selection on male compared with female size.

Home range overlap may select for larger males to deter rivals, defend resources or monopolize females across shared territories, potentially without frequent physical contests.

Our work calls for renewed attention to how spatial competition, including resource defence and mate guarding across overlapping territories, influences trait evolution in primates and other social vertebrates and to re-evaluate proxies of sexual selection."

Territorial conflict may explain male primates’ large size

Effects of between-group competition on sexual size dimorphism in primates (open access)

Fig. 1 In contrast, there was mixed evidence for evolutionary covariation between SSD and the proportion of encounters reported to be agonistic.

If you give an elephant an apple, it will gesture in many different ways for more

Amazing stuff! How intelligent are elephants?

"For elephants, communication is a complicated affair. These massive mammals bellow, trumpet, and rumble at frequencies we humans can’t hear. They detect one another’s seismic waves, touch each other with their trunks, and secrete chemicals from specialized glands. They even address each other with specific, name-like calls and combine visual signals—such as ear-flapping, trunk-swinging, and tail-waggling—with vocalizations when greeting in the wild.

Researchers haven’t confirmed, however, whether these prodigious pachyderms use their gestures to deliberately communicate what they want—a type of behavior known as goal-directed intentionality, which has previously only been observed in primates.

To find out, the authors of a new study presented semi-captive African savannah elephants with two trays: one empty, the other full of apples. The animals ended up using a wide range of gestures , which they only performed when an experimenter was present and looking at them; the animals repeated and elaborated their movements when they failed to receive the desired treats. ..."

From the abstract:

"A crucial feature of language is the ability to communicate cognitive goals to a specific audience, i.e. goal-directed intentionality. Core criteria for this ability include

(i) audience directedness: signalling in the presence of an attentive audience,

(ii) persistence: continuing signalling until goals are met, and

(iii) elaboration: using new signals following communicative failure.

While intentional use has been demonstrated in individual gestures in some non-primates, primates—in particular apes—show this ability across many gestures. But is goal-directed intentionality across many gestures restricted to primates?

We explored whether savannah elephants use many gestures with goal-directed intentionality. We presented semi-captive elephants with desired and non-desired items, recording their communicative attempts when an experimenter met, partially met or failed to meet their goal of getting the desired item.

Elephants used 38 gesture types almost exclusively when a visually attentive experimenter was present, demonstrating audience directedness.

They persisted in gesturing more when their goal was partially as compared with fully met but showed no difference in persistence when the goal was met or not met.

Elephants elaborated their gesturing when their goal was not met. We find goal-directed intentionality across many elephant gestures and reveal that elephants, like apes, assess the communicative effectiveness of their gesturing."

ScienceAdviser

Elephants gesture to signal what they want—just like us "New experiments show elephants use a wide range of movements to express their desires"

Investigating intentionality in elephant gestural communication (open access)

Killer whales groom each other—with pieces of kelp

Amazing stuff!

"In the cold waters of the Salish Sea, just off the coast of British Columbia, you might be able to catch a glimpse of a killer whale’s skincare routine. Using their teeth, the giant ocean predators break off short lengths of bull kelp, a seaweed that looks like a multitailed whip, and place it between their stomach and the belly of another whale. The result is a magnificent image: two killer whales, moving in synchrony, their bodies making a curved “S” shape as they hug a small piece of kelp between them.

This act of mutual exfoliation, which researchers call “allokelping” in a study ... marks the first time aquatic mammals have ever been observed making tools to cooperatively groom each other. ...

Researchers have long known marine mammals can make tools.

Bottlenose dolphins, for example, detach marine sponges and wear them over their noses to protect them from sharp objects on the marine floor as they look for fish to eat.

And whales, which constantly shed their skin like humans do, are no strangers to using tools for grooming. Bowhead whales in the waters near Canada’s Baffin Island sometimes rub themselves on rocks to slough off dead skin, much like humans use pumice stones as an exfoliator. ..."

From the abstract:

"The manufacture and use of tools, while widespread in terrestrial animals, has been less frequently reported in marine taxa. In cetaceans, clear examples of tool use are largely restricted to foraging contexts, with no reports of cetaceans fashioning tools by modifying objects. Here, we report evidence of the widespread manufacture and use of allogrooming tools in a population of resident killer whales (Orcinus orca ater)."

Killer whales groom each other—with pieces of kelp | Science | AAAS "In a newly discovered form of social tool use, orcas scratch each other’s backs with seaweed"

Killer whales make seaweed ‘tools’ to scratch each other’s backs (original news release)

Manufacture and use of allogrooming tools by wild killer whales (open access)

Figure 1 Allokelping in southern resident killer whales.

(A) Fashioning kelp stipes for allokelping. (Left) J41 grasps a kelp stalk by the holdfast end and (right) detaches a short segment.

(B) J19 and J51 allokelping with the kelp stipe visible between them (inset).

(C) J56 exhibiting an S-pose while allokelping with J57 (inverted).

(D) J pod allokelping network. Nodes (circles/squares) represent individuals, while edge (lines) thickness indicates the observed rate of allokelping.

Grey polygons demarcate matrilines. Node size indicates age, shape indicates sex, and color indicates relative level of skin molting as indicated in the legend. ...

Rachel E. John, one of the study authors

Female baboons with close father bonds tend to live longer lives, study finds

Amazing stuff! Father's Day was just last week!

It seems, the article does not say how much genetics was involved or whether the fathers also had a longer than usual lifespan.

Caveat: I did not read the study.

"A team of biologists and wildlife specialists ... and Amboseli Baboon Research Project, in Kenya, has found evidence that female baboons who have relatively strong ties with their fathers while growing up tend to live longer lives. For their study, ... the [team] tracked the lifespans of more than 200 wild female baboons living in Kenya.

Prior research has shown that most primate fathers typically play little to no role in raising their young—humans appear to be the main exception. ..."

From the abstract:

"Parent–offspring relationships can have profound effects on offspring behaviour, health and fitness in adulthood. These effects are strong when parents make heavy investments in offspring care. 

However, in some mammals, including several species of carnivores, rodents and primates, fathers live and socialize with offspring, but paternal care per se is subtle or indirect.

Do these limited father–offspring relationships also affect later-life outcomes for offspring? Working in a well-studied baboon population where males contribute little direct offspring care, we found that juvenile female baboons who had stronger paternal relationships, or who resided longer with their fathers, led adult lives that were 2–4 years longer than females with weak or short paternal relationships.

This pattern did not differ between females who experienced high versus low levels of early-life adversity; hence, paternal relationships were equally protective in both harsh and benign early environments. Males’ relationships were strongest with juvenile females they were most likely to have sired and when males had few mating opportunities. Hence, father–daughter relationships may be constrained by male mating effort. Because survival predicts female fitness, fathers and their daughters may experience selection to engage socially and stay close in daughters’ early lives."

Female baboons with close father bonds tend to live longer lives, study finds

Early-life paternal relationships predict adult female survival in wild baboons (open access)

Credits: Studie: Gute Vaterbeziehung verlängert das Leben junger Pavian-Weibchen

Fig. 2 Juvenile females’ paternal grooming relationships and co-residency predict their adult survival

Superorganism Living worm towers seen in nature for the first time. A case of collective hitchhiking in nature no matter the age of the worm

Amazing stuff! 

Can you believe there is "no role specialization among individuals in towers"!  Old worms can do it too! 😊

"When food runs out and competition heats up, nematodes assemble into living towers. They writhe and twist towards the sky with the goal of latching on to a passing animal to hitch a ride to more comfortable digs.

Scientists had hypothesised this for decades, but no one had seen these aggregations form outside of the laboratory. Now, researchers in Germany have recorded the first video footage of nematodes “towering” in the real world in decaying apples and pears. ..."

"

• First evidence of “living towers” in nature: observed in rotting apples and pears from local orchards in Konstanz, Germany
• Tower function confirmed: towers can attach to passing insects and can bridge physical gaps to disperse
• A powerful model: C. elegans are a new a tool for studying the ecology and evolution of collective dispersal

"

From the highlights and abstract:

"Highlights

• We report the first direct evidence of nematode towers occurring in nature

• Towers can serve to bridge gaps and disperse multiple individuals via phoresy

• Worms from all life stages can tower

• There is no role specialization among individuals in towers

Summary

Dispersal behavior allows organisms to find new resources under harsh conditions; collective dispersal in group-living organisms raises interesting questions about kin selection, cooperation, and social conflicts that offer an exciting window into the evolution of sociality. 

One type of collective dispersal is when individuals physically link their bodies into a super-organism and move as a group, but these phenomena are rare in nature and few empirical systems exist to enable their mechanistic dissection. Individuals of many nematode species can group together and self-assemble into a living tower of worms, which is hypothesized to be a collective dispersal structure. However, direct evidence demonstrating the occurrence and the function of towers in nature has been scarce.

We documented towering behavior under natural, semi-natural, and laboratory conditions to confirm its existence and then manipulated these towers to confirm that they can bridge gaps and respond to external stimuli to confer group dispersal by phoresy. Having established the ecological and functional relevance of nematode towers, we developed a laboratory towering assay with the model organism Caenorhabditis elegans to exploit its experimental capabilities. Our lab assay rapidly and robustly induces towering and reveals several fundamental characteristics of both the towers and the constituent individuals, which together demonstrate the high experimental potential of using our model and the ample future research avenues that it opens.

In summary, combining ecological relevance and empirical possibilities, our work sets the key foundations to establish nematode towering behavior as a powerful opportunity to elucidate the ecology, the mechanisms, and the evolution of collective dispersal."

Living worm towers seen in nature for the first time

Tower power (original news release) "Living worm towers are recorded in the wild for the first time, a rare example of collective hitchhiking in nature"

Towering behavior and collective dispersal in Caenorhabditis nematodes

A tower of fluorescent labelled C.elegans, using a pointed bristle for support

Is this not a cute drawing? One of the researchers is possibly a great fan of Leonardo da Vinci or Albrecht Dürer! 😊 You don't see such drawings very often anymore in scientific works.

Graphical abstract

Reverse engineering the sensory-motor control for schooling in zebrafish using virtual reality

Amazing stuff! This could be a breakthrough!

"... Now, using an immersive virtual reality (VR) setup, scientists have figured out the sensory-motor mechanism underlying this harmonious behavior.

While inside their 3D arena, which researchers dubbed “the Matrix,” individual zebrafish could interact with “holographic” projections of other fish. By analyzing the animals’ reactions and tweaking the movements of virtual “leader” fish, the team determined that “follower” fish used the perceived position—rather than the speed—of their neighbors to guide their own movements. “We were surprised by how little information the fish need to effectively coordinate movements within a school ,” ... Using this natural control law, the researchers programmed a variety of wheeled robots, drones, and robotic watercraft; they were able to follow targets just as well as robots programmed with an existing, state-of-the-art controller—at a fraction of the complexity. ..."

"To the point

• Innovative method: A team of biologists and robotic engineers have developed a virtual reality system for fish to decipher how they school
• Discovering nature’s algorithm: They uncovered the natural ‘control law’ that is used by zebrafish to coordinate behavior with others, a behavioral algorithm that has been tuned over millennia to facilitate effective collective motion.
• Implications for robotics: They tested the natural control law in groups of robotic cars, drones and watercraft, demonstrating its potential for the control autonomous vehicles in the future.

... Using a virtual reality (VR) setup that mimics natural schooling, researchers placed individual juvenile zebrafish into networked arenas where each fish could freely interact with ‘holographic’ virtual conspecifics. Each virtual fish was a projection of a real fish, meaning that fish could swim and interact together in the same virtual world.

The fully immersive 3D environment lets researchers precisely manipulate visual stimuli and record how the fish respond. This high level of control allowed the scientists to isolate exactly which cues the fish were using to guide their interactions with other fish. In other words, they could reverse engineer the behavior of schooling in zebrafish to understand how fish solve the complex problem of coordinating their motion.

The solution, they discovered, was a simple and robust law based only on the perceived position, not the speed, of their neighbors to regulate their following behavior. ..."

From the abstract:

"Revealing the evolved mechanisms that give rise to collective behavior is a central objective in the study of cellular and organismal systems. In addition, understanding the algorithmic basis of social interactions in a causal and quantitative way offers an important foundation for subsequently quantifying social deficits.

Here, with virtual reality technology, we used virtual robot fish to reverse engineer the sensory-motor control of social response during schooling in a vertebrate model: juvenile zebrafish (Danio rerio).

In addition to providing a highly controlled means to understand how zebrafish translate visual input into movement decisions, networking our systems allowed real fish to swim and interact together in the same virtual world. Thus, we were able to directly test models of social interactions in situ.

A key feature of social response is shown to be single- and multitarget-oriented pursuit. This is based on an egocentric representation of the positional information of conspecifics and is highly robust to incomplete sensory input.

We demonstrated, including with a Turing test and a scalability test for pursuit behavior, that all key features of this behavior are accounted for by individuals following a simple experimentally derived proportional derivative control law, which we termed “BioPD.”

Because target pursuit is key to effective control of autonomous vehicles, we evaluated—as a proof of principle—the potential use of this simple evolved control law for human-engineered systems. In doing so, we found close-to-optimal pursuit performance in autonomous vehicle (terrestrial, airborne, and watercraft) pursuit while requiring limited system-specific tuning or optimization."

ScienceAdviser

In VR school, fish teach robots (original news release) "Scientists use virtual reality for fish to teach robots how to swarm"

Reverse engineering the control law for schooling in zebrafish using virtual reality (open access)

Fig. 1. Schematic of the study of SMC of schooling behavior.

Fig. 2. Reverse engineering SMC of fish to a bioinspired proportional-derivative controller, BioPD.

Crows demonstrate abstract geometric intuition comparable to humans

Amazing stuff! How smart are crows, we humans wonder since ancient times!

"Humans have an innate sense for geometry. ...

Researchers first had the clever corvids learn to peck at a particular shape, like a [circle], to get a treat. Then they placed that shape amidst four different ones—stars, for instance. When the birds had no trouble spotting the outlier, the team jacked up the difficulty, asking the animals to spot an irregular quadrilateral amongst a sea of squares. Though monkeys previously failed at this test, the birds excelled. ..."

From the abstract:

"The perception of geometric regularity in shapes, a form of elementary Euclidean geometry, is a fundamental mathematical intuition in humans.

We demonstrate this geometric understanding in an animal, the carrion crow. Crows were trained to detect a visually distinct intruder shape among six concurrent arbitrary shapes. The crows were able to immediately apply this intruder concept to quadrilaterals, identifying the one that exhibited differing geometric properties compared to the others in the set.

The crows exhibited a geometric regularity effect, showing better performance with shapes featuring right angles, parallel lines, or symmetry over more irregular shapes. This performance advantage did not require learning. Our findings suggest that geometric intuitions are not specific to humans but are deeply rooted in biological evolution."

ScienceAdviser

Crows recognize geometric regularity (open access)

Fig. 1. Intruder detection task.

The April 2024 solar eclipse’s darkness caused dawn-singing birds starting to produce their dawn chorus

Amazing stuff! Birds get confused too! 😊🐦

"But the eclipse wasn’t just limited to atmospheric findings. Using more than 10,000 observations from citizen scientists and over 100,000 vocalizations, a team of biologists aimed to find out how birds respond when it suddenly gets dark during the day. They found that, while dusk-singing birds did not change their behavior before or during the eclipse, those that sing in the morning were affected. Their early findings, published as a preprint on bioRxiv, revealed that more than half of wild bird species started singing their dawn chorus after the eclipse, as if it were sunrise. The study highlights the sensitivity of animal behavior to light—in a world where artificial light is on the increase."

From the abstract:

"On April 8th 2024, a total solar eclipse disrupted light-dark cycles for North American birds during the lead-up to spring reproduction. Compiling over 10,000 community observations and AI analyses of nearly 100,000 vocalizations, we found that bird behavior was significantly affected by these few minutes of unexpected afternoon darkness. More than half of wild bird species changed their biological rhythms, with many producing a dawn chorus in the aftermath of the eclipse. This natural experiment demonstrates the power of technology-enabled and public science projects to understand our natural world. Further, it underscores the power of light in structuring animal behavior: even when 'night' lasts for just four minutes, robust behavioral changes ensue."

ScienceAdviser

AI, citizen science, and the 2024 eclipse emphasize the importance of light for bird behavior (open access)

Mice give first aid

Amazing stuff! Do mice also have first responders? 😊

"In emergency situations, humans often exhibit instinctual “first aid” behaviors toward others. Whether and how other species show prosocial behaviors toward others is unclear.

In two independent studies, ... showed that mice exhibit stereotyped behaviors toward unconscious conspecifics, escalating from sniffing and grooming to licking of the head and tongue pulling, which accelerated recovery from unconsciousness  ... 

The activation of neurons in the medial amygdala and oxytocin-expressing neurons in the hypothalamic paraventricular nucleus was required to trigger these behaviors. The results elucidate different aspects of a previously unrecognized prosocial behavior in mice and its underlying neurobiological mechanisms."

From the abstract:

"Structured Abstract

INTRODUCTION

The partial or complete loss of responsiveness, such as transient unconsciousness, presents a substantial risk to animals, increasing their vulnerability to predators or hazardous environments.

The actions of bystanders toward unresponsive individuals can be critical for enhancing survival and well-being. Humans, for instance, can readily recognize and assist unconscious individuals.

Similarly, anecdotal reports suggest that some animal species, including nonhuman primates, marine mammals (e.g., whales and dolphins), and elephants, exhibit behavioral reactions to collapsed or unresponsive conspecifics in the wild. However, it is unclear whether such behaviors occur in species beyond those few that have been documented.

Additionally, the nature, characteristics, and consequences of these behaviors have not been systematically examined in a controlled experimental setting. Moreover, the neural mechanisms underlying the perception of others’ unresponsive states and the ensuing behaviors remain elusive.

RATIONALE

Previous studies have demonstrated that rodents, including mice, can perceive and behaviorally respond to others’ negative or needy states.

For example, they can display comforting social touch through allogrooming, broadly targeted at various body parts of distressed conspecifics. In addition, they can respond to others’ local pain and injury with allolicking behavior focused on the wound site.

However, it is unclear how mice react to other animals in an unresponsive state. In this study, we examined the behaviors that mice display toward unresponsive conspecifics, their effects on the recipients, and the neural representation and regulation of these behaviors.

RESULTS

We discovered that mice preferentially approach unresponsive conspecifics over awake ones and engage in distinctive behaviors toward unresponsive conspecifics under deep sedation, characterized by intense contact and grooming directed at the sedated individuals’ head region, particularly the facial and mouth areas. These behaviors are observed in both male and female animals and are correlated with the extent of reduction in the responsiveness of the recipients.

Physical contact and grooming directed at the head region are more likely to elicit motor responses in the recipients compared with other social behaviors and can expedite the animals’ recovery from the unresponsive state.

Moreover, we uncovered an essential role of the medial amygdala (MeA) in regulating this response. MeA neural activity differentiates between awake and sedated conspecifics at both single-cell and population levels, and the neural response to sedated animals does not simply reflect a response to novelty. Optogenetic silencing of MeA γ-aminobutyric acid–producing (GABAergic) neurons suppresses head grooming behavior, whereas their activation promotes this behavior. Although mice respond to sedated, unresponsive conspecifics primarily with head-directed allogrooming and physical contact, their allogrooming response to awake conspecifics experiencing a general state of stress mainly targets other body regions.

These two different adverse states and the corresponding behavioral responses (head grooming versus body grooming) are distinguishable by neural activities in the MeA, suggesting that the MeA may be part of the neural circuitry mediating the differentiation between these states.

CONCLUSION

Our findings reveal that mice exhibit rescue-like behaviors toward unresponsive conspecifics, characterized by intense physical contact directed at the recipient’s head region. This response accelerates recovery from unresponsiveness, potentially reducing risks to unresponsive individuals and enhancing their survival. We have also uncovered that the MeA encodes the unresponsive state of others and drives head-directed grooming toward them.

Notably, the behavioral response toward unresponsive conspecifics differs from that toward awake, stressed individuals, and these responses are differentially represented in the MeA. These findings shed light on the neural mechanisms underlying prosocial responses toward unresponsive individuals, broadening our understanding of animals’ ability to detect and behaviorally react to different adverse conditions of others."

In Science Journals | Science

A neural basis for prosocial behavior toward unresponsive individuals

Reviving-like prosocial behavior in response to unconscious or dead conspecifics in rodents

Prosocial behavior toward unresponsive conspecifics.

Mouse behaviors toward an unconscious peer.

Male chimps ask with gestures for sex in different ‘dialects’ and they vary by community

Amazing stuff! 

The convenient and usual blame on humans should be discounted!

"Just like humans, chimpanzees have different “dialects”—in the gestures they use to communicate. A new study has found that males from different chimp communities in the Taï National Park in Ivory Coast use different gestures to signal to females that they’re in the mood for sex.

Male chimps can make various moves to show they want some “sneaky copulation on the side,” ... When Wittig’s team looked at records of 495 of these gestures in four neighboring chimp communities, they found clear differences. In two of the four groups, for example, males tore strips from leaves to request sex. Another gesture, the “knuckle knock”—repeatedly knocking knuckles onto a tree or another hard surface—occurred in only one. ..."

From the abstract:

"The horizontal transmission of cultural knowledge is a powerful mechanism of evolutionary change. Across taxa, group-specific cultural traditions are expressed in diverse contexts, such as foraging, tool use, self-care and socialization. These traditions arise when group members converge on specific behavioral phenotypes. When these behavioral phenotypes involve communicative signals, such as gestures, they are termed dialects.

However, gestural dialects are rare in non-humans. Behavioral phenotypes and traditions can also be lost, a well-documented phenomenon in humans, but rarely documented in non-human animals. Here, we find that chimpanzee gestures produced in copulation solicitations show culturally established phenotypes and undergo cultural loss due to human-induced population decline."

ScienceAdviser

Male chimps ask for sex in different ‘dialects’ "Gestures are in danger because of poaching and other human pressures"

Signal traditions and cultural loss in chimpanzees (open access)

Figure 1 Evidence for socially derived gesture dialects in chimpanzees.

Echolocating bats use cognitive maps of sound to find their way home in the dark

Amazing stuff!

Why did they choose such tiny bats to attach a GPS device? "Study with 6-gram light bats"

"... In a new study, researchers placed GPS trackers on tiny pipistrelle bats living in Israel’s Hula Valley and relocated them to various points within a three-kilometer radius. Some of the animals were also blindfolded or had their sense of smell blocked. Surprisingly, even when forced to rely on echolocation alone, 95% of bats were able to find their way back to their roosts within minutes. The findings suggest that this ability allows bats to create complex mental “maps” of their surroundings, complete with various types of acoustic “landmarks,” which they use to navigate across long distances.

The researchers were also surprised to discover that, when possible, the bats used their vision to enhance navigation. ... even with such small eyes, they can rely on vision under these conditions.” ..."

"... In addition to the field experiments, the team created a detailed map of the entire valley. “We wanted to visualize what each bat experienced during flight and understand how they used acoustic information to navigate,”  ...

The model revealed that bats tend to fly near environmental features with higher ‘echoic entropy'—areas that provide richer acoustic information. “During the localization phase, bats conduct a meandering flight that, at a certain point, changes to a directional flight toward their destination, suggesting they already know where they are ..."

From the editor's summary and abstract:

"Editor’s summary

Insectivorous bats are well known to use echolocation to catch prey and navigate around obstacles. It has also been shown that more visually guided fruit bats have spatial cognitive maps of their environment. Goldshtein et al. placed minuscule GPS trackers on tiny pipistrelle bats in conjunction with temporary blocks of vision and olfaction. The authors found that the bats could still navigate across kilometer scales using only echolocation. Thus, echolocation may not only allow for local navigation, but might also translate into an acoustic cognitive map of the environment that the animals can use to navigate over long distances. —Sacha Vignieri

Abstract

Bats are known for their ability to use echolocation for obstacle avoidance and orientation. However, the extent to which bats utilize their highly local and directional echolocation for kilometer-scale navigation is unknown. In this study, we translocated wild Kuhl’s pipistrelle bats and tracked their homing abilities while manipulating their visual, magnetic, and olfactory sensing and accurately tracked them using a new reverse GPS system. We show that bats can identify their location after translocation and conduct several-kilometer map-based navigation using solely echolocation. This proposition was further supported by a large-scale echolocation model disclosing how bats use environmental acoustic information to perform acoustic cognitive map–based navigation. We also demonstrate that navigation is improved when using both echolocation and vision."

ScienceAdvisor

Echolocating bats use an acoustic cognitive map for navigation

Bats use an acoustic cognitive map for navigation (original news release)

Echolocating bats use an acoustic cognitive map for navigation (no public access)

Kissing may have gotten its start as an ape grooming ritual

As if we did not know that! 😊 Did the kiss become more common with human fur-loss?

"... Clay tablets from Ancient Mesopotamia dating to 2500 B.C.E. provide the earliest archaeological evidence of romantic kissing. The behavior may even be older than civilization itself, with some studies suggesting neanderthals swapped spit with modern humans— and shared each other’s oral microbes—more than 100,000 years ago. ...

Why did humans start kissing in the first place? Some researchers have suggested it evolved from sniffing, nursing babies, or even parents passing chewed-up food to their children. But in an article published last week in Evolutionary Anthropology, evolutionary psychologist Adriano Lameira suggests that kissing got its start as a fur grooming ritual still observed in modern-day chimpanzees and other great apes. After searching through its companion’s coat for parasites or debris, he explains, one ape will typically pucker its lips and remove the offending item with its mouth. ..."

From the abstract:

"A kiss has been a signal of special affection across continents and cultures for millennia. Between times and peoples, social norms invariably prescribe kissing to specific affiliations and contexts, implying deeper biological bases. Why the protruding of the lips and slight suction when touching another? Capuchin monkeys stick their fingers in their friends' eyes as sign of affection, why have humans developed kissing? Here I briefly review proposed hypotheses for the evolution of human kissing. Great ape social behavior suggests that kissing is likely the conserved final mouth-contact stage of a grooming bout when the groomer sucks with protruded lips the fur or skin of the groomed to latch on debris or a parasite. The hygienic relevance of grooming decreased over human evolution due to fur-loss, but shorter sessions would have predictably retained a final “kissing” stage, ultimately, remaining the only vestige of a once ritualistic behavior for signaling and strengthening social and kinship ties in an ancestral ape."

ScienceAdvisor

The evolutionary origin of human kissing (open access)

"Did the first kiss look like this?"

How Dice snakes fake their own gory deaths

What a bizarre behavior! That some  animals fake death to escape predators has been known for a long time.

"Aspiring actors in need of inspiration for their next dramatic death scene needn’t look any further than dice snakes (Natrix tessellate). The serpents fake their own deaths to avoid predators.

In a bizarre new finding, researchers have discovered dice snakes include dramatic practical effects in their charade such as smearing themselves with faeces and oozing blood from their mouths. Snakes which do this are more effective actors and spend less time feigning death overall. ..."

From the abstract:

"Predation exerts a significant selection pressure on prey, shaping a multitude of traits that serve as antipredator defences. In turn, natural selection could favour combinations of antipredator defences with synergistic effects that enhance prey survival. An especially interesting antipredator defence is death feigning (DF), present in a wide variety of taxa and usually characterized by the prey lying motionless often along with defaecation, musking and autohaemorrhaging (AH). All these aspects of the DF display should work in conjunction with one another, intensifying the overall effect of the display and in turn facilitating quicker escape. To confirm this hypothesis, we tested 263 dice snakes (Natrix tessellata) directly in the field. We noted the occurrence of smearing faeces, musk and AH, and we measured the duration of DF, expecting to see a negative association between the occurrence of these behaviours and the duration of DF. Our results affirm our hypothesis: dice snakes that smeared themselves in musk and faeces prior to DF and had AH during DF spent significantly less time in DF. Our results highlight the functional integration of antipredator behaviours across different phases of predator–prey interactions, emphasizing the need for future research to prioritize studying the sequential display of behaviours."

Dice snakes fake their own gory deaths

Synergistic effects of musking and autohaemorrhaging on the duration of death feigning in dice snakes (Natrix tessellata) (no public access)

Immersive full field of view VR goggles for mice could advance neuroscience research

How cute is that? We have humanized mice wearing VR goggles!

What kind of videos would you like to show a mouse?

"... One possible solution to overcome these challenges could be to use virtual reality (VR) or augmented reality (AR) technology to observe how mice behave and how their brain responds when they are virtually exposed to specific scenes or situations. While several research teams have been trying to develop VR goggles or headsets for mice, none of the solutions developed so far cover the animals' entire field of view, which could lead to delayed or different responses from those that the mice would have in real-world settings. ..."

"... “For the past 15 years, we have been using VR systems for mice,” ... “So far, labs have been using big computer or projection screens to surround an animal. ..."

From the significance and abstract:

"Highlights

• iMRSIV (Miniature Rodent Stereo Illumination VR), a new mouse VR goggle system

• iMRSIV is small and provides stereo vision and an ∼180° field of view per eye

• Mice using iMRSIV engaged in virtual behaviors more quickly than in current VR

• iMRSIV is compatible with two-photon imaging and overhead looming paradigms

Summary

Visual virtual reality (VR) systems for head-fixed mice offer advantages over real-world studies for investigating the neural circuitry underlying behavior. However, current VR approaches do not fully cover the visual field of view of mice, do not stereoscopically illuminate the binocular zone, and leave the lab frame visible. To overcome these limitations, we developed iMRSIV (Miniature Rodent Stereo Illumination VR)—VR goggles for mice. Our system is compact, separately illuminates each eye for stereo vision, and provides each eye with an ∼180° field of view, thus excluding the lab frame while accommodating saccades. Mice using iMRSIV while navigating engaged in virtual behaviors more quickly than in a current monitor-based system and displayed freezing and fleeing reactions to overhead looming stimulation. Using iMRSIV with two-photon functional imaging, we found large populations of hippocampal place cells during virtual navigation, global remapping during environment changes, and unique responses of place cell ensembles to overhead looming stimulation."

Miniature VR goggles for mice could advance neuroscience research

Immersive VR goggles for mice unlock new potential for brain science (Northwestern University) Goggles enabled researchers to study responses to overhead threats for first time

Full field-of-view virtual reality goggles for mice (open access)

Graphical abstract

Is the biological evolution of face recognition a curse or a blessing?

Probably both or in between! As so often in life and reality, it is complicated.

Just learnt that the ability of face recognition may have lead to individuals of one population being aggressive to individual strangers from the same population (see my blog post here).

Pregnancy programs the brain for mothering with hormones

Amazing stuff! The power of hormones!

From the abstract of the perspective:

"Pregnancy requires extensive physiological remodeling to provide the energy required for gestating a fetus and delivering and nurturing a newborn. Successful mothering requires an additional finely tuned behavioral repertoire. In most mammals, this starts with retrieval to a nest, grooming, and nursing. Estradiol and progesterone, the same pregnancy hormones that remodel the body, also program the brain for mothering, but precisely how this occurs has been opaque. ... report the identification of galanin neurons in the medial preoptic area (MPOA) as the cellular target of steroid programming in mice. Estradiol and progesterone changed the activity of galanin neurons such that the sensitivity to stimuli emanating from the pups (e.g., odors and vocalizations) was much stronger. New synapses were also formed on the galanin neurons. These remarkably specific changes were sufficient to promote mothering behavior."

From the editor's summary and abstract:

"Motherhood leads to pronounced behavioral changes in many species, such as altered feeding routines and increased aggressivity. How does pregnancy prepare females for such future behavioral needs? ... discovered that the hormonal milieu of pregnancy remodels a distinct population of hypothalamic neurons in mice ... that mediates the onset of parental behavior before giving birth. Sensing of estradiol and progesterone by galanin-expressing neurons in the medial preoptic area is necessary for this behavioral change. Therefore, hormone-mediated neuronal modifications lead to an increased selectivity for pup stimuli, thus anticipating future parenting behaviors. ...
Abstract

During pregnancy, physiological adaptations prepare the female body for the challenges of motherhood. Becoming a parent also requires behavioral adaptations. Such adaptations can occur as early as during pregnancy, but how pregnancy hormones remodel parenting circuits to instruct preparatory behavioral changes remains unknown. We found that action of estradiol and progesterone on galanin (Gal)–expressing neurons in the mouse medial preoptic area (MPOA) is critical for pregnancy-induced parental behavior. Whereas estradiol silences MPOAGal neurons and paradoxically increases their excitability, progesterone permanently rewires this circuit node by promoting dendritic spine formation and recruitment of excitatory synaptic inputs. This MPOAGal-specific neural remodeling sparsens population activity in vivo and results in persistently stronger, more selective responses to pup stimuli. Pregnancy hormones thus remodel parenting circuits in anticipation of future behavioral need."

Pregnancy programs the brain for mothering | Science (no public access) Progesterone and estrogen exert separate effects on the brains of pregnant mice

Hormone-mediated neural remodeling orchestrates parenting onset during pregnancy (no public access)

Tickled rats reveal brain structure that controls laughter

Amazing stuff! Who says that science is mostly serious? 😊

"... Of all mammalian behaviors, play is one of the least understood ... “Neuroscience tends to focus very much on aversive things,” ... such as the brain regions behind aggression and fear. Play remains a mystery. “There’s relatively little research on positive emotions,” ... “which I tend to think is a mistake.” ...

The research that does exist shows rats will keep playing even after their entire cortex, the part of the brain essential for consciousness and higher level behaviors, has been destroyed. This suggests that play, like fear, is instinctual. Some studies propose that a structure called the periaqueductal gray (PAG), which plays a role in vocalization, the fight-or-flight response, and other behaviors, might be involved. When rats play fight with one another, they exhibit behaviors that mimic fear and aggression. ...

Rats are capable of particularly complex forms of play similar to those seen in humans ... In one previous experiment, ... team even taught the rodents to play hide and seek. At the beginning of the game, a rat was enclosed in a box while a researcher hid somewhere in the room. The researcher then opened the box using a remote control, allowing the animal to jump out and begin “seeking.” When the rat successfully found the hidden scientist, it was rewarded with—you guessed it—a tickle. The rats were also given the opportunity to hide while the researchers looked for them, and they proved to be especially good at coming up with creative hiding spots. Their ability to strategize was “almost spooky,” ...
Past experiments have shown that when certain animals are deprived of play, they become depressed, fail to form relationships, and are less resilient to stressful situations. Lack of play has even been shown to stunt brain development. ..."

Tickled rats reveal brain structure that controls laughter | Science | AAAS Rodents’ squeaks may shed light on the neural mechanisms of play in humans

Rats “laugh” when tickled, although this sound is too high- pitched for humans to hear

Dogs can literally smell when you're stressed

As if dog owners did not know that already for many, many years!

Dogs can literally smell when you're stressed Dogs can not only read stress on your face [questionable!], but also smell it dripping through your pores.

Dogs can discriminate between human baseline and psychological stress condition odours (open access)

Fig 1. Timeline of the data collection process for the in-person protocol.