Slacker rat, worker rat Rodent work ethic, like people’s, comes in two types

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Slacker rat, worker rat

Rodent work ethic, like people’s, comes in two types

By Laura Sanders

Web edition : 10:27 am

When it comes to intellectual challenges, rats, like people, fall naturally into categories of slackers and workers. And a shot of stimulant sometimes gets slackers to work harder while prompting the workers to ease off, researchers report online March 28 in Neuropsychopharmacology.

Hard work can come in many forms. Animal studies that explore the costs and benefits of such tasks usually involve rodents physically working, such as pushing a lever or scaling a wall for a reward. But those kinds of experiments don’t account for mental effort, says Jay Hosking of the University of British Columbia in Vancouver.

“We were trying to find something that modeled a little more closely what you see in the human experience,” Hosking says. “In everyday life, it’s the cognitive side where people really have to make those decisions, like whether you work harder throughout the day in hopes of getting a promotion, or coast through and check Facebook every 15 minutes and earn your wages.”

In the study’s rodent analog of a work day, rats poked their nose into one of five holes to indicate the location of a flash of light. By pushing a lever before the trial began, the rats chose either an easy version or a hard one. In the easy task, the light shone for a full second, making its location easy to spot. In the hard version, the light briefly flashed for a fifth of a second, a time so brief that the rats had to really concentrate to choose the right hole. The harder task came with double the sugar-pellet reward.

When compared to the average behavior, some individuals reliably went for the easy version and collected their small reward. Other animals overwhelmingly chose the intellectually harder route. Not only do these divisions between what the team termed slackers and workers exist, the researchers showed, but the differences persist across many trials.

“This article opens up a new area related to mental effort,” says behavioral neuroscientist John Salamone of the University of Connecticut in Storrs. For instance, scientists can now start to explore the relationship between physical and mental work.

Giving rats the stimulants amphetamine and caffeine produced varied effects depending on individual’s personality, the team found. For slacker rats, amphetamine sharpened the mental work ethic, making the animals more likely to choose the harder task. But for workers, amphetamine caused the animals to choose the easier option more. Meanwhile, caffeine turned worker rats into slackers, but didn’t make the slackers work any harder.

The researchers can’t yet explain why stimulants would cause workers to choose the easier task. One possibility is that hard workers are already performing optimally, so anything that swings the system out of whack, such as stimulants, could cause a net decrease in productivity.

More generally, the results show that drugs aren’t necessarily one-size-fits-all, Salamone says.


  1. Why did they use rats?

  2. Why did they use a mental task instead of a physical task?

  3. What was the task?

  4. What was the reward?

  5. What were the results?

  6. What drugs did they give the rats to alter their choices?

  7. What effect did the drugs have on their choices?

  8. Write at least 3 sentences describing your opinion or comments about this article.

The sun, the moon and the Titanic

By Meg Urry, Special to CNN

updated 5:06 PM EDT, Sun March 18, 2012

The ill-fated White Star liner RMS Titanic, which struck an iceberg and sank on her maiden voyage across the Atlantic.

Editor's note: Meg Urry is the Israel Munson professor of physics and astronomy and chairwoman of the department of physics at Yale University, where she is the director of the Yale Center for Astronomy and Astrophysics. This article was written in association with The Op-Ed Project.

(CNN) -- Blaming the moon is a popular pastime. Police say crime rates go up during a full moon, nurses claim birth rates go up, authors set werewolves and vampires loose upon the land, and people think craziness abounds -- witness the word "lunatic," which derives from "luna," the Latin word for moon.

None of this moon-linked strangeness has ever stood up to serious scrutiny. But now a team of astronomers at Texas State University-San Marcos has suggested that the moon can be blamed for the sinking of the Titanic on its maiden voyage 100 years ago.

How the moon caused icebergs to litter the Titanic's path, on April 14, 1912, is really a story about the Earth's tides. What we now know about where icebergs originate and how they travel could have informed the Titanic's crew and perhaps avoided tragedy. But at the time, this science was in its infancy.

The Titanic's captain did not expect icebergs to be a problem -- rarely did ice travel so far south into the Atlantic. Yet contemporaneous warnings from other ships suggested there were an unusual number of icebergs. Passengers reported seeing ice floes, lookouts spotted ice and sounded warnings, and other ships in the area reported fields of ice near the disaster site.

Here's where astronomy comes in: Three months earlier, on January 4, 1912, the closest approach of the moon to the Earth in 1,400 years occurred within one day of the Earth's closest approach to the sun (which occurs once per year), all within minutes of a full moon, meaning the sun was perfectly aligned on the other side of the Earth (this happens every couple of weeks). The odds of all three events occurring at once are, well, astronomical.

This lineup had to have caused unusually high tides in the North Atlantic. Tides are caused mostly by the differential pull of the moon's gravity on the Earth. The pull is strongest on the near side and weakest on the far side, since the strength of gravity, as Isaac Newton told us four centuries ago, falls as the square of the distance between the two massive objects -- in this case, the Earth and the moon.

That is, the moon pulls hardest on the Earth's oceans on the side facing the moon, making a bulge of water (high tide). It pulls less hard on the Earth, but even less hard on the water on the far side, so a watery bulge forms on the far side as well -- a high tide roughly 12 hours out of synch.

The overall strength of the moon's gravity, as well as its differential (tidal) effect, is greatest when the moon is closest to the Earth, as on January 4, 1912.

Now consider the sun. It is much more massive than the moon or Earth but also much farther away. The absolute pull of the sun's gravity is far greater than the pull of the moon -- that's why we're orbiting the sun, after all, rather than the moon -- but the sun does not exert much of a tidal force on the Earth (that is, a stronger force on the Earth's near side than its far side) because, compared to the distance between the sun and Earth, the Earth's size is miniscule.

Try this analogy (thanks to if the Earth were the size of a basketball, the moon would be a tennis ball about 24 feet away, and the Sun would be like a house nearly two miles away. To the sun, the Earth is a tiny speck: its diameter is less than 0.01% of the Earth-sun distance. But the size of the Earth is a few percent of the distance to the moon, which translates to about a 7% stronger gravitational pull on the near side of the Earth than the far side. That's why the moon dominates the Earth's tides.

Still, when the sun lines up perfectly on the opposite side of the Earth from the moon, as it did on January 4, 1912, it increases the tidal effect slightly. And the fact that the sun and moon were particularly close to the Earth at precisely the same time -- well, that made the tidal bulges even bigger.

What does this have to do with icebergs? The University of Texas scientists pointed out that normally, icebergs move south from Greenland in fits and starts, frequently grounding in the shallow waters off Labrador and Newfoundland. But unusually high tides in January 1912 meant the icebergs didn't get stuck. Instead, they kept moving south, arriving in much greater numbers than usual in the path of the Titanic.

Maybe the Titanic's captain had reason to believe reports of excessive ice were wrong -- such conditions were, after all, not the norm. But he didn't reckon on the inexorable pull of gravity from Earth's nearest celestial neighbor. This is the real lunar influence on our lives: gravity and tides, not werewolves and pregnant women.

One thing this new theory predicts: There should be records of exceptionally high tides near Newfoundland and Labrador in January 1912. This is the hallmark of a proper theory: it makes predictions that can then be tested.

So, history buffs, marine historians, tell us: Does this theory hold water?


  1. What strange things are sometimes blamed on the moon?

  2. What impact might the moon had on the Titanic?

  3. What happened in January 1912?

  4. How often does this happen?

  5. What effect does the moon have on tides?

  6. What effect does the sun have on tides compared to the moon? Why?

  7. What do iceburgs from the north usually do when they move south?

  8. What happened differently that might have caused the Titanic to sink?

  9. Write at least 2 sentences about your thoughts on this theory.

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