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Crows are self-aware just like us, says new study
Crows have their own version of the human cerebral cortex.
It's no surprise that corvids — the "crow family" of birds that also includes ravens, jays, magpies, and nutcrackers — are smart. They use tools, recognize faces, leave gifts for people they like, and there's even a video on Facebook showing a crow nudging a stubborn little hedgehog out of traffic. Corvids will also drop rocks into water to push floating food their way.
What is perhaps surprising is what the authors of a new study published last week in the journal Science have found: Crows are capable of thinking about their own thoughts as they work out problems. This is a level of self-awareness previously believed to signify the kind of higher intelligence that only humans and possibly a few other mammals possess. A crow knows what a crow knows, and if this brings the word sentience to your mind, you may be right.
It's long been assumed that higher intellectual functioning is strictly the product of a layered cerebral cortex. But bird brains are different. The authors of the study found crows' unlayered but neuron-dense pallium may play a similar role for the avians. Supporting this possibility, another study published last week in Science finds that the neuroanatomy of pigeons and barn owls may also support higher intelligence.
"It has been a good week for bird brains!" crow expert John Marzluff of the University of Washington tells Stat. (He was not involved in either study.)
Corvids are known to be as mentally capable as monkeys and great apes. However, bird neurons are so much smaller that their palliums actually contain more of them than would be found in an equivalent-sized primate cortex. This may constitute a clue regarding their expansive mental capabilities.
In any event, there appears to be a general correspondence between the number of neurons an animal has in its pallium and its intelligence, says Suzana Herculano-Houzel in her commentary on both new studies for Science. Humans, she says, sit "satisfyingly" atop this comparative chart, having even more neurons there than elephants, despite our much smaller body size. It's estimated that crow brains have about 1.5 billion neurons.
Fun with Ozzie and Glenn
Ozzie and Glenn not pictured
The kind of higher intelligence crows exhibited in the new research is similar to the way we solve problems. We catalog relevant knowledge and then explore different combinations of what we know to arrive at an action or solution.
The researchers, led by neurobiologist Andreas Nieder of the University of Tübingen in Germany, trained two carrion crows (Corvus corone), Ozzie and Glenn.
The crows were trained to watch for a flash — which didn't always appear — and then peck at a red or blue target to register whether or not a flash of light was seen. Ozzie and Glenn were also taught to understand a changing "rule key" that specified whether red or blue signified the presence of a flash with the other color signifying that no flash occurred.
In each round of a test, after a flash did or didn't appear, the crows were presented a rule key describing the current meaning of the red and blue targets, after which they pecked their response.
This sequence prevented the crows from simply rehearsing their response on auto-pilot, so to speak. In each test, they had to take the entire process from the top, seeing a flash or no flash, and then figuring out which target to peck.
As all this occurred, the researchers monitored their neuronal activity. When Ozzie or Glenn saw a flash, sensory neurons fired and then stopped as the bird worked out which target to peck. When there was no flash, no firing of the sensory neurons was observed before the crow paused to figure out the correct target.
Nieder's interpretation of this sequence is that Ozzie or Glenn had to see or not see a flash, deliberately note that there had or hadn't been a flash — exhibiting self-awareness of what had just been experienced — and then, in a few moments, connect that recollection to their knowledge of the current rule key before pecking the correct target.
During those few moments after the sensory neuron activity had died down, Nieder reported activity among a large population of neurons as the crows put the pieces together preparing to report what they'd seen. Among the busy areas in the crows' brains during this phase of the sequence was, not surprisingly, the pallium.
Overall, the study may eliminate the layered cerebral cortex as a requirement for higher intelligence. As we learn more about the intelligence of crows, we can at least say with some certainty that it would be wise to avoid angering one.
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Humans are particularly prone to shiver when a group does or thinks the same thing at the same time.
A few years ago, I proposed that the feeling of cold in one's spine, while for example watching a film or listening to music, corresponds to an event when our vital need for cognition is satisfied.
A growing body of research suggests COVID-19 can cause neurological damage in some patients.
- The study examined data of cognitive performance collected from more than 84,000 people, more than 12,000 of whom had likely contracted and recovered from COVID-19.
- Compared to healthy participants, the COVID-19 group performed significantly worse on cognitive tests.
- Mental decline in the worst cases were the equivalent of ageing by 10 years.
The effect size of cognitive deficits varied across three cognitive domains, which were estimated by applying principal component analysis with varimax rotation to the nine test summary scores.
Hampshire et al.<p>Participants who suffered the most severe cases of COVID-19, and had to be put on a respirator, showed cognitive "equivalent to the average 10-year decline in global performance between the ages of 20 to 70." For comparison, the study notes that the difference in cognitive performance between this group and the control "equates to an 8.5-point difference in IQ."<br></p><p>The COVID-19 group scored particularly low on tests measuring semantic problem solving and visual selective attention.</p><p style="margin-left: 20px;">"People who have recovered from COVID-19 infection show particularly pronounced problems in multiple aspects of higher cognitive or 'executive' function, an observation that accords with preliminary reports of executive dysfunction in some patients at hospital discharge," the researchers wrote.</p><p>Considering that all participants had recovered from the disease when they completed the cognitive tests, the results suggest that "COVID-19 infection likely has consequences for cognitive function that persist into the recovery phase," the researchers wrote.</p><p>Still, it's unclear whether these deficits (if indeed caused by COVID-19) are permanent, or how long they may last. But there is evidence suggesting that severe respiratory conditions can cause neurological damage. A <a href="https://link.springer.com/article/10.1186/s13054-019-2626-z" target="_blank">2011 study</a>, for example, found that people who'd been hospitalized with acute respiratory distress syndrome can suffer cognitive deficits that persist up to five years after discharge.</p>
The Block Rearrange test [featured in the Great British Intelligence Test] measures spatial problem solving.
Credit: Hampshire et al.<p>It's worth noting the study is limited, mainly because it didn't compare before-and-after cognitive performance of the COVID-19 group. Another possible limitation: People with lower cognitive abilities may be more likely to contract COVID-19 because they're more likely to put themselves in harm's way.</p><p style="margin-left: 20px;">"We consider such a relationship plausible; however, it would not explain why the observed deficits varied in scale with respiratory symptom severity," the researchers wrote. "We also note that the large and socioeconomically diverse nature of the cohort enabled us to include many potentially confounding variables in our analysis."</p>
San Diego-area hospitals treat coronavirus patients during COVID-19 pandemic
Credit: Mario Tama/Getty Images<p>Only time and further research will tell whether COVID-19 leaves people with lasting cognitive deficits. Scientists are already establishing long-term research projects to answer these questions, such as the <a href="https://www.cambridgebrainsciences.com/studies/covid-brain-study" target="_blank" rel="noopener noreferrer">COVID-19 Brain Study</a>, which aims to monitor the long-term health of 50,000 participants who have tested positive for the disease.</p><p>If you've been diagnosed with COVID-19 and want to enroll in the study, visit <a href="https://www.cambridgebrainsciences.com/studies/covid-brain-study" target="_blank" rel="noopener noreferrer">cambridgebrainsciences.com/studies/covid-brain-study</a>.</p>