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Left-eyed Lizards


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I recently came across an article entitled ‘Advantages in exploring a new environment with the left eye in lizards’ and I couldn’t help but read more.

The common wall lizard is found across Europe and N America

In this study, conducted in Italy, scientists caught 44 wall lizards and glued eye patches on to them (using a paper glue that is harmless to the lizards as they can shed and renew their skin). Half the lizards had their left eye covered, and half had their right eye covered.

The lizards were then let into a maze for 20 minutes to see how they fared with turning left and right. The ones that were allowed to use just their left eye were much faster than those that could just use their right eye at turning both left and right. In addition to this, they made fewer stops, seeming to be less hesitant and indecisive than the right-eyed individuals. However, this was only the case when the lizard had to make a choice between turning left or right, not when they only had the choice to turn one way.

Why might this be the case? Well, like a lot of vertebrates, lizards have lateralized brains. This means that the brain is divided in two halves, and some functions are specialized to one half. The classic example of this in humans is Broca’s area (associated with speech), which is found in the left hemisphere of the brain in 95% of us.

Similar to how humans on the whole prefer to use their right hand, it seems that lizards generally prefer to use their left eye. As with humans, lizard optic nerve fibres are crossed over, meaning that control of the left eye comes from the right hemisphere of the brain and vice versa. As these lizards predominantly use their left eye, this indicates that in this species, something in the right side of their brain is specialised in attending to spatial cues.

Photo credits

First lizard: Mircea Nita

Second lizard: Donald Hobern

 

Reference

Bonati, B., Csermely, D., & Sovrano, V. A. (2013). Advantages in exploring a new environment with the left eye in lizards. Behavioural processes. 97: 80-83.

 

Felicity Muth About the Author: Felicity Muth is an early-career researcher with a PhD in animal cognition. Follow on Twitter @notbadscience.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. N a g n o s t i c 4:23 pm 06/10/2013

    SA must be running around with a toothpick keeping its Obama administration adoring eye wide open, its critical eye stitched closed.

    My comment is definitely off-topic. This caused by the absence of a very important topic within the august confines of SA.

    A week and counting, and the brave Edward Snowden and NSA’s Prism program are being reported everywhere – except here at Scientific American. One sycophantic, government apologist article posted June 8th doesn’t qualify as reporting. It’s positively embarrassing.

    This is quite puzzling to me… cryptographic even. The same revelations during the Bush administration would’ve generated plenty of negative SA editorializing and blogging; they did just that, over similar news of a lesser nature at the time.

    I suppose it’s better to see very little spoken here concerning a story in continuing development everywhere else, as SA and its bloggers would probably blame Bush as their counterparts at NYT, WP, MSNBC and CBS did reflexively. Those guys came across as administration lapdogs who got scooped by the British paper. Instead of doing journalism, they’re acting as organs of the state, so far. Scientific American is only being uncharacteristically mum. Perhaps they’re getting their ideological house in order.

    I can’t help but notice Snowden isn’t blaming Bush – he’s blaming the guy he voted for, our current president. How appropriate of him. No sycophantic rust jamming his ideological gears. He voted for the current administration, and has the intellectual honesty to act on his rightful dismay – risking his life in the process.

    What a brave man – he’s a true hero.

    Link to this
  2. 2. Andrew Planet 6:53 pm 06/10/2013

    Though it important to let you know, I saw a documentary(BBC I think) a few months ago which shed the same results for experiments on the left human eye. I’ll look for it tomorrow as its late now but I’m sure that info is out there. How else would I already know that info which makes me proud of only seeing well with my left eye?

    Link to this
  3. 3. Felicity Muth in reply to Felicity Muth 12:19 am 06/11/2013

    You’re right- in addition to most humans preferring to use their right hand, they also tend to use their right eye, although I think it’s a bit less than the proportion of people that are right-handed.

    Link to this
  4. 4. lamorpa 9:14 am 06/11/2013

    N a g n o s t i c,

    Be quiet. No one is interested in your uncontrolled obsessions. If you want particular content in a magazine, put together one of your own. You look like nothing but a complete whining fool.

    Just as relevant, on the subject of whales: Call me Ishmael. Some years ago — never mind how long precisely — having little or no money in my purse, and nothing particular to interest me on shore, I thought I would sail about a little and see the watery part of the world. It is a way I have of driving off the spleen, and regulating the circulation. Whenever I find myself growing grim about the mouth; whenever it is a damp, drizzly November in my soul; whenever I find myself involuntarily pausing before coffin warehouses, and bringing up the rear of every funeral I meet; and especially whenever my hypos get such an upper hand of me, that it requires a strong moral principle to prevent me from deliberately stepping into the street, and methodically knocking people’s hats off — then, I account it high time to get to sea as soon as I can. This is my substitute for pistol and ball. With a philosophical flourish Cato throws himself upon his sword; I quietly take to the ship. There is nothing surprising in this. If they but knew it, almost all men in their degree, some time or other, cherish very nearly the same feelings towards the ocean with me.

    There now is your insular city of the Manhattoes, belted round by wharves as Indian isles by coral reefs — commerce surrounds it with her surf. Right and left, the streets take you waterward. Its extreme down-town is the battery, where that noble mole is washed by waves, and cooled by breezes, which a few hours previous were out of sight of land. Look at the crowds of water-gazers there.

    Circumambulate the city of a dreamy Sabbath afternoon. Go from Corlears Hook to Coenties Slip, and from thence, by Whitehall northward. What do you see? — Posted like silent sentinels all around the town, stand thousands upon thousands of mortal men fixed in ocean reveries. Some leaning against the spiles; some seated upon the pier-heads; some looking over the bulwarks of ships from China; some high aloft in the rigging, as if striving to get a still better seaward peep. But these are all landsmen; of week days pent up in lath and plaster — tied to counters, nailed to benches, clinched to desks. How then is this? Are the green fields gone? What do they here?

    But look! here come more crowds, pacing straight for the water, and seemingly bound for a dive. Strange! Nothing will content them but the extremest limit of the land; loitering under the shady lee of yonder warehouses will not suffice. No. They must get just as nigh the water as they possibly can without falling in. And there they stand — miles of them — leagues. Inlanders all, they come from lanes and alleys, streets and avenues, — north, east, south, and west. Yet here they all unite. Tell me, does the magnetic virtue of the needles of the compasses of all those ships attract them thither?

    Once more. Say, you are in the country; in some high land of lakes. Take almost any path you please, and ten to one it carries you down in a dale, and leaves you there by a pool in the stream. There is magic in it. Let the most absent- minded of men be plunged in his deepest reveries — stand that man on his legs, set his feet a-going, and he will infallibly lead you to water, if water there be in all that region. Should you ever be athirst in the great American desert, try this experiment, if your caravan happen to be supplied with a metaphysical professor. Yes, as every one knows, meditation and water are wedded for ever.

    But here is an artist. He desires to paint you the dreamiest, shadiest, quietest, most enchanting bit of romantic landscape in all the valley of the Saco. What is the chief element he employs? There stand his trees, each with a hollow trunk, as if a hermit and a crucifix were within; and here sleeps his meadow, and there sleep his cattle; and up from yonder cottage goes a sleepy smoke. Deep into distant woodlands winds a mazy way, reaching to overlapping spurs of mountains bathed in their hill-side blue. But though the picture lies thus tranced, and though this pine-tree shakes down its sighs like leaves upon this shepherd’s head, yet all were vain, unless the shepherd’s eye were fixed upon the magic stream before him. Go visit the Prairies in June,…

    Link to this
  5. 5. HMichaelPower 3:26 pm 06/11/2013

    Felicity, thanks for the pointer to a fascinating article. If you are interested in lateralization, you should read Iain McGilchrist’s magisterial synthesis and interpretation of the evidence on lateralization in the brains of humans and other animals. The book has around 2500 references.

    http://www.iainmcgilchrist.com/

    The left hemisphere is specialized for broad attention to the environment while the right hemisphere is specialized for narrow focussed attention – so birds tend to use their right eye to scan the skies for predators and their left eye to focus on food morsels on the ground.

    Link to this
  6. 6. Felicity Muth in reply to Felicity Muth 5:58 pm 06/11/2013

    Interesting! Thanks for the link

    Link to this
  7. 7. SteveM 7:26 pm 06/11/2013

    I seem to be missing part of the explanation for this interesting phenomenon. The left hemisphere processes the right visual field from both eyes, and similarly, the right hemisphere processes the left side from both eyes – the optic chiasm splits the visual fields accordingly. So the left eyed lizards are still sending visual signals to both sides of the brain.

    Link to this

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