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Do zebra finches (Taeniopygia guttata) have true polarization vision?

Melgar, Julian (2013) BION26 20131
Degree Projects in Biology
Abstract
Abstract

Despite the fact that many animals have been found to use the angle of polarization of light in a number of different contexts, the behavioral and physiological mechanisms behind vertebrate polarization light sensitivity remain largely unidentified. In this study I have used modified LCD-monitors to produce polarization stimuli, and behavioral conditioning experiments to assess true polarization vision in zebra finches. The birds were trained to discriminate rewarded from unrewarded alternatives presented by color and brightness contrast stimuli or polarization angle contrast stimuli. Although all the experimental zebra finches were able to discriminate color and brightness contrast stimuli, only one of the birds was able to... (More)
Abstract

Despite the fact that many animals have been found to use the angle of polarization of light in a number of different contexts, the behavioral and physiological mechanisms behind vertebrate polarization light sensitivity remain largely unidentified. In this study I have used modified LCD-monitors to produce polarization stimuli, and behavioral conditioning experiments to assess true polarization vision in zebra finches. The birds were trained to discriminate rewarded from unrewarded alternatives presented by color and brightness contrast stimuli or polarization angle contrast stimuli. Although all the experimental zebra finches were able to discriminate color and brightness contrast stimuli, only one of the birds was able to discriminate polarization stimuli. The results suggest that zebra finches are not, at any biologically relevant level, capable of discriminating polarization stimuli. (Less)
Abstract
Popular science summary:

What the zebra finches did not see

There is more out there than what we can see; that is something that most people would agree on. And I am not talking about ghosts from the beyond or aliens from space; I am talking about all those things that we know exist but that we are not able to see with our own eyes or feel with our own senses. I am not talking science fiction, I am talking sensory biology.

There are so many things we don’t see. Take light for instance. Light is probably the most ordinary thing for most humans; everything we see is, technically speaking, light (seeing is after all nothing else than our way of reacting to light), but yet there are so many things in light that we cannot see,... (More)
Popular science summary:

What the zebra finches did not see

There is more out there than what we can see; that is something that most people would agree on. And I am not talking about ghosts from the beyond or aliens from space; I am talking about all those things that we know exist but that we are not able to see with our own eyes or feel with our own senses. I am not talking science fiction, I am talking sensory biology.

There are so many things we don’t see. Take light for instance. Light is probably the most ordinary thing for most humans; everything we see is, technically speaking, light (seeing is after all nothing else than our way of reacting to light), but yet there are so many things in light that we cannot see, UV-light for example, or infrared light.
As a matter of fact, we humans see only two of the three known dimensions of light. We see color and we see brightness, but there is a third dimension, polarization, to which we are almost complete-ly blind.
This third dimension is defined by the angle of oscillation of the electric field of light, an electric wave that oscillates along the direction of propagation of light, and which, in the same way as brightness and color, can change when light is reflected or scattered by objects or particles. In con-sequence, polarization can potentially provide information about the surroundings in a similar way as, and additionally to, brightness or color.

Many animals have been found to use the angle of polarization of light in a number of different contexts, but for birds, and vertebrates in general, the behavioral and physiological mechanisms be-hind polarization light sensitivity are still a mystery. I therefore decided to try to solve, at least a part of the mystery, by studying the capacity of zebra finches to learn a simple task with the help of po-larization stimuli.
I modified two LCD-screens to be able to produce images that consisted only of polarization, the other two dimensions, color and brightness, were excluded from the picture. I used those images, in combination with normal color pictures, to train the birds to find a reward in a two-choice experi-ment where one of the options, the rewarded option, was signaled by either a color picture or a po-larization picture.
All the zebra finches learned to find the reward when it was signaled by color pictures, but only one of the birds was able to do the trick whit polarization pictures. And even he, despite hard train-ing, wasn’t very good at it.

My results left me with more questions than answers, but something is clear: it is extremely difficult to train zebra finches to react to polarization stimuli. Whether this depends on an intrinsic avian inability of perceiving the polarization angle of light, as some authors suggest, or on my own inca-pability of designing an appropriated experiment, is at the moment a question with no answer. And vertebrate light polarization sensitivity remains one of the hard nuts of sensory biology.


Advisors: Rachel Muheim and Olle Lind
Master’s degree project (45credits) in sensory biology, 2013.
Department of Biology, Lund University. (Less)
Please use this url to cite or link to this publication:
author
Melgar, Julian
supervisor
organization
course
BION26 20131
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
4117166
date added to LUP
2013-10-22 14:23:14
date last changed
2013-10-22 14:23:14
@misc{4117166,
  abstract     = {Popular science summary:

What the zebra finches did not see

There is more out there than what we can see; that is something that most people would agree on. And I am not talking about ghosts from the beyond or aliens from space; I am talking about all those things that we know exist but that we are not able to see with our own eyes or feel with our own senses. I am not talking science fiction, I am talking sensory biology.
 
There are so many things we don’t see. Take light for instance. Light is probably the most ordinary thing for most humans; everything we see is, technically speaking, light (seeing is after all nothing else than our way of reacting to light), but yet there are so many things in light that we cannot see, UV-light for example, or infrared light. 
 As a matter of fact, we humans see only two of the three known dimensions of light. We see color and we see brightness, but there is a third dimension, polarization, to which we are almost complete-ly blind.
 This third dimension is defined by the angle of oscillation of the electric field of light, an electric wave that oscillates along the direction of propagation of light, and which, in the same way as brightness and color, can change when light is reflected or scattered by objects or particles. In con-sequence, polarization can potentially provide information about the surroundings in a similar way as, and additionally to, brightness or color.

 Many animals have been found to use the angle of polarization of light in a number of different contexts, but for birds, and vertebrates in general, the behavioral and physiological mechanisms be-hind polarization light sensitivity are still a mystery. I therefore decided to try to solve, at least a part of the mystery, by studying the capacity of zebra finches to learn a simple task with the help of po-larization stimuli. 
 I modified two LCD-screens to be able to produce images that consisted only of polarization, the other two dimensions, color and brightness, were excluded from the picture. I used those images, in combination with normal color pictures, to train the birds to find a reward in a two-choice experi-ment where one of the options, the rewarded option, was signaled by either a color picture or a po-larization picture. 
 All the zebra finches learned to find the reward when it was signaled by color pictures, but only one of the birds was able to do the trick whit polarization pictures. And even he, despite hard train-ing, wasn’t very good at it.
 
 My results left me with more questions than answers, but something is clear: it is extremely difficult to train zebra finches to react to polarization stimuli. Whether this depends on an intrinsic avian inability of perceiving the polarization angle of light, as some authors suggest, or on my own inca-pability of designing an appropriated experiment, is at the moment a question with no answer. And vertebrate light polarization sensitivity remains one of the hard nuts of sensory biology.


Advisors: Rachel Muheim and Olle Lind
Master’s degree project (45credits) in sensory biology, 2013.
Department of Biology, Lund University.},
  author       = {Melgar, Julian},
  language     = {eng},
  note         = {Student Paper},
  title        = {Do zebra finches (Taeniopygia guttata) have true polarization vision?},
  year         = {2013},
}