Category: Comparative

Here’s The First Evidence That Even Lizards Succumb To Optical Illusions

Central bearded dragon on the rock

By Emma Young

It’s been known for centuries that we experience all kinds of optical illusions, and in the past few decades, researchers have shown that some animals, including monkeys, pigeons, and dogs, do too. Now the first ever study of this kind in reptiles has found that even the bearded dragon falls for an optical illusion that we humans succumb to.

Perceptual illusions — subjective interpretations of physical information — are interesting to psychologists because they reveal important insights into how we construct our representations of the world. This new work, published in the Journal of Comparative Psychology, provides evidence that at least one reptile can be counted among the animals don’t simply passively process retinal signals, but actively interpret visual data, too.

Continue reading “Here’s The First Evidence That Even Lizards Succumb To Optical Illusions”

Researchers Have Identified An Area of The Dog Brain Dedicated To Processing Human Faces

Screen Shot 2019-01-02 at 16.42.26.png
The human brain (a) and dog brain (b), from Thompkins et al, 2018

By Christian Jarrett

If you want to know about the special relationship between human and canine you need only watch a dog owner slavishly feed, cuddle and clean up after her furry companion, day after day after day. But is this unique cross-species relationship also reflected at a deeper level, in the workings of the canine brain? A recent study in Learning and Behavior suggests so, finding that highly trained dogs have a dedicated neural area for processing human faces, separate from the area involved in processing the faces of other dogs.

The researchers, led by Andie Thompkins at Auburn University, say their results are of theoretical importance (in relation to the evolutionary origin of cognitive abilities) and could have practical use too, potentially paving the way to using brain scans to validate the expertise of trained dogs.

Continue reading “Researchers Have Identified An Area of The Dog Brain Dedicated To Processing Human Faces”

10 Of The Most Famous Animals In Psychology

GettyImages-140472681.jpgBy Christian Jarrett

Psychologists have long studied chimps and other animals with two principal, related aims: to find out the capabilities of the animal mind, and to discover what makes us truly unique, if anything. This is a challenging field. As any pet owner knows, it’s tempting to project a human interpretation onto animal behaviour. Researchers, especially when they’ve spent many years studying the same animal, can fall victim to this very bias (you’ll see a theme of this field is the powerful, close bonds frequently formed between psychologist and animal). At the same time, though, there is also a temptation to overestimate our human uniqueness. Which emotions and capabilities are exclusively human? Tool use, perspective taking and deceit were once contenders, but no more, and the list is getting shorter all the time.

This Digest feature post is a celebration of the contribution that animals have made to psychology, including eight that we’ve come to know on first-name terms:

Continue reading “10 Of The Most Famous Animals In Psychology”

The Psychology of Sex Differences – 5 Revealing Insights From Our Primate Cousins

By Christian Jarrett

There are behavioural differences, on average, between the sexes – few would dispute that. Where the debate rages is over how much these differences are the result of social pressures versus being rooted in our biology (the answer often is that there is a complex interaction between the two).

For example, when differences are observed between girls and boys, such as in preferences for play, one possibility is that this is partly or wholly because of the contrasting ways that girls and boys are influenced by their peers, parents and other adults (because of the ideas they have about how the sexes ought to behave). Studying non-human primates allows us to identity sex differences in behavior that can’t be due to human culture and gender beliefs.

Learning more about the biological roots of behavioural sex differences should not be used as an excuse for harmful stereotyping or discrimination, but it can help us better understand our human nature and the part that evolved sex differences play in some of the most important issues that affect our lives, including around diversity, relationships, mental health, crime and education.

Earlier this year, as part of a special issue of the Journal of Neuroscience Research – titled “An Issue Whose Time Has Come: Sex/Gender Influences on Nervous System Function” – Elizabeth Lonsdorf at Franklin and Marshall College published a useful mini-review detailing some of the sex differences observed among monkey and ape infants and juveniles.

“Many sex differences in behavioral development exist in nonhuman primates,” she writes, “despite a comparative lack of sex-biased treatment by mothers and other social partners”. Here is a digested account of five of these behavioural sex differences:   

Continue reading “The Psychology of Sex Differences – 5 Revealing Insights From Our Primate Cousins”

Lazy bees and clean hyenas: Review finds that animals vary in trait conscientiousness

GettyImages-164307835.jpgBy Emma Young

Conscientiousness is a fundamental aspect of human personality, with higher levels associated with all kinds of benefits, from greater academic achievement and relationship stability to living for longer.  Yet it’s the only major human personality dimension not to have been widely identified in animals, which poses an evolutionary puzzle – if animals don’t show signs of conscientiousness, where did the human variety come from? But now a major review of hundreds of relevant papers, published in Psychological Bulletin, concludes that in fact, “there are many documented examples of conscientiousness behaviour in other animals”. The work also suggests that there are two main branches to conscientiousness, each associated with an evolutionary drive to solve different types of problems.

Continue reading “Lazy bees and clean hyenas: Review finds that animals vary in trait conscientiousness”

Researchers are studying psychopathic chimps to better understand the human variety

GettyImages-584864828.jpgBy Emma Young

To understand the drivers of a psychopathic personality (marked by callousness, disinhibition and superficial charm), it’s worth looking at our closest relatives. Some chimps, like some people, score highly on scales designed to evaluate psychopathic tendencies. And new work in Frontiers in Neuroscience reveals a potentially important genetic contributor to psychopathic traits in chimps, which could lead to a better understanding of the traits in people.

Continue reading “Researchers are studying psychopathic chimps to better understand the human variety”

The idea that humans have a poor sense of smell is an outdated myth, argues new review

The Nose For Wine
It’s estimated that humans may be able to distinguish up to a trillion different smells

By Alex Fradera

In the early 1950s, while investigating rabbits’ sense of smell by recording the activity of their brain cells, the scientist Lord Adrian noticed something curious. As his team mixed up odours of increasing strength, to see at what point the rabbits’ neurons fired in response, they found the critical threshold appeared around the same point that they were able to smell the odour themselves: in other words, this suggested that the smell had become noticeable to animal and man at the same time.

On publication of the research, Lord Adrian mentioned his observation, but it didn’t provoke a serious response, presumably because informed scientists knew that the human sense of smell is generally pathetic. Everyone knew… but they knew wrong. In a new review in Science, John McGann, who runs the Rutgers Laboratory on the Neurobiology of Sensory Cognition, takes us through the historical misunderstandings to reach the truth about what the human nose knows.

Continue reading “The idea that humans have a poor sense of smell is an outdated myth, argues new review”

Brain scan study reveals dogs attend to word meaning, not just intonation

By guest blogger Sofia Deleniv

Imagine if we could capture the words of an angry dog owner holding a chewed-up shoe – “How could you? You terrible dog!” – and digitally alter the tone to sound praising. Would the dog be oblivious to the reprimanding content of the message? I should admit that, until quite recently, I thought that the answer was yes ­– that no matter how chastising the words you used, you could convince a dog that it is being showered in praise, simply by adopting an affectionate tone. But a recent study published in Science indicates that many of us might be vastly underestimating canine listening skills. The findings reveal that dogs do not rely exclusively on intonation when judging the reward value of human speech, but that they also recognise the meanings that we assign to words. Continue reading “Brain scan study reveals dogs attend to word meaning, not just intonation”

New clues about the way memory works in infancy

Neurons in the beautiful background. 3d illustration of a highBy Alex Fradera 

Can we form memories when we are very young? Humans and non-humans alike show an “infantile amnesic period” – we have no memory of anything that happens during this time (usually up to age three or four in humans) which might suggest we can’t form very early memories. But of course it might be that we can form memories in these early years, it’s just that they are later forgotten. The idea that at least something is retained from infancy is consistent with the fact that disorders present in adult life can be associated with very early life events.

Now Nature Neuroscience has published a paper confirming that in rats some kind of memories are created during the amnesic period, but that these operate differently and are produced by different brain chemistry from adult memories. What’s more, such events may have a role in kickstarting memory system maturation. Continue reading “New clues about the way memory works in infancy”

Pessimistic rats are extra sensitive to negative feedback

By guest blogger Mary Bates

Depression is complex and influenced by many factors, but the way depressed people think is a likely contributor to the disorder. Depression is often associated with cognitive biases, including paying more attention to negative than positive events and recalling them more easily. People with depression also tend to ruminate over perceived failures and criticism, and they are extra sensitive to negative feedback.

Analogous cognitive biases can be found in animals. Now, in a new study, researchers have demonstrated for the first time a link between pessimism and sensitivity to performance feedback in rats. It’s the latest finding to show parallels between human depression and rat pessimism – an important result that lends further legitimacy to using animal research to shed light on human psychological problems.

You might wonder how on earth it is possible to measure pessimism in rats.  One way to do this was shown in a 2004 study in which animals were trained to press a lever to receive a food reward in response to hearing one tone, and to press a different lever to avoid a mild electric shock upon hearing a different tone. Then the scientists presented the animals with intermediate tones, in between the ones that signaled either food or shock. Which lever the rats pressed in response to these ambiguous cues was considered an indicator of whether the animals expected a positive or negative event. In other words, their behaviour revealed their relative optimism or pessimism.

In the new research, Rafal Rygula and Piotr Popik of the Polish Academy of Sciences used the same paradigm to compare the reaction of rats displaying optimistic and pessimistic traits to positive and negative feedback. First, they divided rats into two groups based on how they performed in the ambiguous-cue interpretation test. Some rats tended to interpret ambiguous cues as signaling a reward, indicating a positive cognitive bias, while others were more likely to interpret them as signaling punishment, indicating a bias toward more pessimistic judgments.

Then the optimistic and pessimistic rats were trained and tested in a probabilistic reversal-learning (PRL) task, which essentially involves using negative or positive feedback to teach the animals to change or maintain a response that they’ve learned previously. Rygula and Popik determined how likely each rat was to switch its response after receiving negative feedback and to maintain its response following positive feedback.

The researchers found that the two groups did not differ in their responses to positive feedback, but that pessimistic rats were more sensitive to negative feedback than optimistic rats. That is, the pessimistic rats were much quicker to drop a previously learned response once it started to be met with negative feedback – you could see this as akin to a depressed human giving up more quickly in response to criticism.

This new finding builds on earlier research by Rygula and his colleagues, in which they demonstrated that the trait of pessimism can also influence rats’ motivation levels (the optimistic rats were more motivated than pessimistic rats to obtain a sip of sugary water), and their vulnerability to “stress-induced anhedonia” – after being restrained, which they find stressful, pessimistic rats showed a longer-lasting lost appetite for sugary water. This might represent a reduction in their ability to experience pleasure that is analogous to human anhedonia, which is another important symptom of depression.

This new study on sensitivity to negative feedback in pessimistic rats, in combination with Rygula’s two previous studies, supports the claim that rats that tend to be pessimistic are also more likely to demonstrate a variety of behavioral and cognitive processes that are linked with increased vulnerability to depression.

It’s hard to know how similar pessimistic rats are to depressed people, but studies like these certainly provide intriguing commonalities. Scientists use animals such as rats as models for human disorders like depression, and use such models to test new therapies and drugs. It seems that rats can display the same negative cognitive biases as people, tending to make negative judgments about events and interpreting ambiguous cues unfavorably. And these biases, in turn, affect both rats’ and humans’ sensitivity to negative feedback.

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Post written by Mary Bates (@mebwriter) for the BPS Research Digest. Mary is a freelance science writer specialising in the brains and behaviour of humans and other animals. She has been published in National Geographic News, National Geographic’s Weird & Wild blog, New Scientist, the Society for Neuroscience’s BrainFacts website, plus many other outlets. She earned her PhD from Brown University, where she researched bat echolocation and bullfrog chorusing. You can follow her on Twitter and Facebook and see all of her work at her website.

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