The Challenge of Measuring a Bird Brain

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In research, infrequently environment out to denote one judgment indeed formula in proof something wholly different. It’s critical to be flexible.

Take, for example, Corina Logan, whose work focuses on a cognitive abilities of a great-tailed grackle, a member of a blackbird family. A youth investigate associate during UC Santa Barbara’s SAGE Center for a Study of a Mind when she conducted her research, Logan sought to find a approach to accurately estimate a mind distance of live grackles by measuring their heads rather than a inside of their skulls.

A masculine great-tailed grackle. Image credit: Richard Ditch

A masculine great-tailed grackle. Image credit: Richard Ditch

Instead, she detected that a process biologists and other scientists have been regulating to review mind distance opposite class is not suitable for looking during particular differences within a class — utterly this species. Her findings, upheld by a National Geographic Society/Waitt Grants Program, are published in a erudite biography PeerJ.

“People adore to investigate mind size,” pronounced Logan, now a Leverhulme Early Career Research Fellow in a Department of Zoology during a University of Cambridge. “It’s a outrageous topic. And there is flourishing seductiveness in how mind distance varies within a species, that can tell us what factors minister to a expansion of vast brains.”

To know what’s going on within a species, Logan continued, we have to know how to magnitude their brains. And if we wish to investigate furious class though murdering your subjects, we have to figure out a approach to magnitude their smarts though stealing them from their particular skulls.

“That’s what we was perplexing to do — investigate them in a furious after measuring them so we could see either their mind distance influences their function or a series of brood they have,” she explained. “I was perplexing to magnitude mind distance though measuring their tangible brains.”

So Logan and co-author Christin Palmstrom, an undergraduate tyro in biology when a investigate was conducted, acquired skulls from museums and totalled them around dual methods: They used CT scans to magnitude a volume of a inside of a braincase and they used calipers to magnitude a outmost skull. The scanned a skulls and afterwards used mechanism program to calculate a endocranial volume, which, according to Logan, is a common substitute for mind size. The CT indicate was a some-more accurate process for calculating endocranial volume, to that they compared length, breadth and tallness measurements a done regulating a calipers.

A grackle skull. Image credit: Sonia Fernandez

A grackle skull. Image credit:
Sonia Fernandez

“If a outmost skull measurements matched a volumes from a CT scans good enough, afterwards we could use a CT indicate or caliper methods interchangeably,” Logan said.

They don’t.

According to Logan, it’s unfit to estimate mind distance regulating a outmost skull dimensions since it varies so many within this species. That was startling to her on a integrate of levels. “First, we was astounded that a outmost skull measurements did not accurately envision a tangible endocranial volumes,” she said. “But we was also astounded that there was so many variation, utterly in males.”

Scientists don’t generally tell disastrous formula — i.e. not anticipating what they’re looking for — though in this case, Logan’s astonishing outcome is utterly interesting. She demonstrated that a Pearson product-moment association coefficient, that is ordinarily used to magnitude a grade to that dual variables describe to any other (such as a dual surreptitious measures of mind size), is not a right exam to request to these data. It overlooks differences in a particular information points, she noted, that was a whole indicate of a study.

“People see a ‘significant correlation’ between dual sets of measurements and consider it works,” Logan said. “But it’s mostly not a unequivocally parsimonious correlation. There is an overreliance on any turn of association as prolonged as it’s significant.”

So Logan motionless to try a opposite investigate to endorse — or not — how good a outmost skull measurements estimate endocranial volume calculations. Her question: If we accumulate information from new skulls, how good will these outmost skull measurements envision endocranial volume regulating a CT indicate process if we don’t indeed CT indicate a skulls?

“What we found is that if we block in a new number, we can’t tell it detached from a other numbers in a information set since a prophecy intervals for many of a information points overlapped with any other,” she said. “So a outmost skull measurements aren’t helpful. They don’t tell us what their mind distance indeed is.” The results, she added, stress a significance of validating and categorically quantifying a predictive correctness of mind distance proxies for any class and sex.

According to Logan, scientists can no longer take for postulated what has formerly been dynamic as accurate and correct. “Statistical methods in biology are in motion right now,” she said. “People are switching from regulating statistics formed on p-values, like a Pearson correlation, to methods that concede one to demeanour during a finer sum of a effects occurring in a information set.”

Key to a success of this research, according to Logan was UCSB’s Cheadle Center for Biodiversity and Ecological Restoration (CCBER), that preserves and manages mixed healthy story collections, including plants, animals, algae and diatoms. This “amazing resource,” as she described it, enabled Palmstrom, to accumulate a required information for a investigate project. And for that she indispensable a vast adequate series of total grackle skulls for this species, that aren’t accessible in California.

“Christin was doing some proffer work during CCBER and found out they could steal a specimens from other museums,” pronounced Logan. In this case, CCBER borrowed grackle skulls from a Museum of Southwestern Biology in Albuquerque, New Mexico, and a University of Kansas Biodiversity Institute to finish a representation size, that also enclosed one skull from a Santa Barbara Museum of Natural History.

“So Christin would wait for a skulls to arrive and afterwards go to CCBER to magnitude them,” Logan went on. “Collections manager Mireia Beas-Moix rubbed all and helped us find some-more skulls. Usually investigate dollars are parsimonious and no one has a resources to offer assistance like this, though CCBER was a resources of support.”

In her work, Logan studies live birds rather than skeletons, though as she said, “Working with museum specimens can fill a unequivocally critical square of a nonplus for me.

Source: UC Santa Barbara