Tuesday, March 4, 2014

Cunning Pigeons and their Head-Bobbing Illusion

For as long backward as my memories can take me, I have been surrounded by the same winged creatures in public domains, especially when I am holding or consuming food like sandwiches or fried chips: pigeons. And for that entire time, and the now, I have wondered, why is it that these demanding beings continuously bob their heads back and forth whilst they walk, increasing the speed of this movement when their legs move faster?

So, to feed my inquisitive mind, I had decided for my one-hundredth essay to embark on a minor research journey to find out and inform others about why pigeons look as though they are listening to rock and roll music when they walk. My findings have proven to be interesting, seeing as I found a research document which tested the head movement motives of two pigeons by walking them on a treadmill. This already shows that others in this vast world are looking into why these mysterious and hungry creatures seek to portray having an epileptic fit whenever they are mobile. 

The 'Optokinetic Basis of Head-bobbing in the Pigeon' was conducted in 1977 by B. J. Frost. It found, for the time in which the research took place, astounding results which ruled out that pigeons do not actually 'bob' their heads in a forward and backward motion - ultimately, they thrust their heads backward and their bodies forward, making it look as though they are head-bobbing. This was determined by the thorough studying of Frost, wherein he firstly took observational notes of feral pigeons around his university, a 'natural setting'. He came to two hypotheses from this observation: that one, pigeons bobbed their heads to maintain their sense of equilibrium, or balance, and two, that the head-bobbing was indicative of a visual response involving periods of stabilisation of the pigeon's perception of the world and objects close and far.

Frost then placed two pigeons on a treadmill, covered the area of the treadmill with a clear plexiglass box in order to stop the pigeons from flying off, and began to observe their bodily movements at an average walking speed, the speed in which they quickly adapted. Frost noticed that the head-bobbing movements were unrelated to the pigeons' leg and foot movements. He also noticed that because the pigeons' leg speeds matched that of the treadmill's motor speed, their heads did not bob at all. They had already maintained balance, or equilibrium from their adaptation of the motor speed.

The breakthrough point of the experiment happened inadvertently, when a pigeon was on the treadmill and instead of abruptly turning the treadmill off, the person conducting the test had slowed it down. The pigeon on the treadmill then slowly pushed forward until it lost its balance and 'toppled' over. The speed was not sufficient enough for the pigeon to sustain its walking and balance, so it simply fell. The fact that it moved itself forward slowly partly revealed that it does not 'bob' its head. 

High-speed motion photography had predominantly found the reason as to why pigeon's heads do not 'bob' - it had captured a pigeon landing from flight and walking - it showed that just after landing, pigeons appear to head-bob to balance themselves out, however it is because of the 'figure of eight' movement of their wingtips that an illusion is created, wherein an onlooker wrongly sees its head bobbing. What actually is happening to its head is that it is 'proceed[ing] smoothly through space'.  Its head moves backwards, and its body lunges forward at the same time, stabilising its body, and assisting it in detecting objects in motion with the thrusting back of its head. 

The pigeon's head movements thus are 'compensatory' to error signals sent to its brains, and it moves its head backward, thrusts its body forward in order to regain balance. We have underestimated pigeons. Well, at least I have. I remember chasing them back in my high school days because it made them appear to bob their heads faster, when in actuality they were panicking, stabilising themselves and looking ahead at other potential human threats. They simply could not yet fly off, they would risk loss of possible foods being left behind. Pigeons are full of deceit, but unlucky for them we now know their secrets thanks to the assistance of high-speed photography.


                                                                                                                                                                                         

References:

B.J Frost's research paper:
[http://wexler.free.fr/library/files/frost%20(1978)%20the%20optokinetic%20basis%20of%20head-bobbing%20in%20the%20pigeon.pdf]

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