Field of View and Eye Movements
Some animals, usually but not always prey animals, have their two eyes positioned on opposite sides of their heads to give the widest possible field of view. Examples include rabbits, buffaloes, and antelopes. In such animals, the eyes often move independently to increase the field of view. Even without moving their eyes, some birds have a 360-degree field of view.
Other animals, usually but not always predatory animals, have their two eyes positioned on the front of their heads, thereby allowing for binocular vision and reducing their field of view in favor of stereopsis. Examples include humans, eagles, wolves, and snakes.
Some predator animals, particularly large ones such as sperm whales and killer whales, have their two eyes positioned on opposite sides of their heads. Other animals that are not necessarily predators, such as fruit bats and a number of primates also have forward facing eyes. These are usually animals that need fine depth discrimination/perception; for instance, binocular vision improves the ability to pick a chosen fruit or to find and grasp a particular branch.
In animals with forward-facing eyes, the eyes usually move together.
When the eyes move laterally, in the same direction, this is called a version. When the eyes move in opposite directions, to an object closer than where the eyes are pointing or farther than where the eyes are pointing, this is called a vergence. When the eyes move in, it is a convergence eye movement; when the eyes move out, it is a divergence eye movement.
Some animals (including some humans, notably exotropes) use both of the above strategies. A starling, for example, has laterally placed eyes to cover a wide field of view, but can also move them together to point to the front so their fields overlap giving stereopsis. A remarkable example is the chameleon, whose eyes appear to be mounted on turrets, each moving independently of the other, up or down, left or right. Nevertheless, the chameleon can bring both of its eyes to bear on a single object when it is hunting, showing vergence and stereopsis.
Read more about this topic: Binocular Vision
Famous quotes containing the words field of, field, view, eye and/or movements:
“I would say that deconstruction is affirmation rather than questioning, in a sense which is not positive: I would distinguish between the positive, or positions, and affirmations. I think that deconstruction is affirmative rather than questioning: this affirmation goes through some radical questioning, but it is not questioning in the field of analysis.”
—Jacques Derrida (b. 1930)
“You cannot go into any field or wood, but it will seem as if every stone had been turned, and the bark on every tree ripped up. But, after all, it is much easier to discover than to see when the cover is off. It has been well said that “the attitude of inspection is prone.” Wisdom does not inspect, but behold.”
—Henry David Thoreau (1817–1862)
“To see self-sufficiency as the hallmark of maturity conveys a view of adult life that is at odds with the human condition, a view that cannot sustain the kinds of long-term commitments and involvements with other people that are necessary for raising and educating a child or for citizenship in a democratic society.”
—Carol Gilligan (20th century)
“With an eye made quiet by the power
Of harmony, and the deep power of joy,
We see into the life of things.”
—William Wordsworth (1770–1850)
“The novel is not “a crazy quilt of bits”; it is a logical sequence of psychological events: the movements of stars may seem crazy to the simpleton, but wise men know the comets come back.”
—Vladimir Nabokov (1899–1977)