mental processes:

A study by University of Stirling psychologists found that children who avoid eye contact while considering their responses to questions had higher rates of correct answers than children who maintained eye contact.One researcher theorized that looking at human faces requires a lot of mental processing, which detracts from the cognitive task at hand. Researchers also noted that a blank stare indicated a lack of understanding.

Dr. Gwyneth Doherty-Sneddon was quotedas having said, "Looking at faces is quite mentally demanding. We get useful information from the face when listening to someone, but human faces are very stimulating and all this takes processing. So when we are trying to concentrate and process something else that's mentally demanding, it's unhelpful to look at faces."

Among different species:

The eye contact between non-human mammals and between humans and other mammals is also well documented. Young children may be more likely to fall victim to dog attacks because they maintain eye contact, which the dog perceives as aggression, according to a report in the New Zealand Medical Journal.

In many species, eye contact is often perceived as a threat. All programs to prevent dog bites recommend avoiding direct eye contact with an unknown dog.

In the 1990’s, black bears returned to Maryland's Catoctin Mountain Park after a twenty-year absence. Visitors are recommended to avoid direct eye contact if the bear stands on its hind legs. Chimpanzees use eye contact to signal aggression in hostile encounters, and staring at them in a zoo can induce agitated behavior.

Comparisons with other mammals reveals that homo sapiens secrete tears as an emotional response. Other terrestrial mammals do not express their emotions by weeping. Additionally, the diameter of the pupil is highly dependent on the hormonal balance, and therefore on the emotional state as is the iris colour.

EVIL EYE:

In some forms, it is the belief that some people can bestow a curse on victims by the malevolent gaze of their magical eye. The most common form, however, attributes the cause to envy, with the envious person casting the evil eye doing so unintentionally. Also the effects on victims vary. Some cultures report afflictions with bad luck; others believe the evil eye can cause disease, wasting away, and even death. In most cultures, the primary victims are thought to be babies and young children, because they are so often praised and commented upon by strangers or by childless women. The late UC Berkeley professor of folklore Alan Dundes has explored the beliefs of many cultures and found a commonality — that the evil caused by the gaze is specifically connected to symptoms of drying, desiccation, withering, and dehydration, that its cure is related to moistness, and that the immunity from the evil eye that fish have in some cultures is related to the fact that they are always wet. His essay "Wet and Dry: The Evil Eye" is a standard text on the subject.

In many forms of the evil eye belief, a person — otherwise not malefic in any way — can harm adults, children, livestock, or a possession, simply by looking at them with envy. The word "evil" can be seen as somewhat misleading in this context, because it suggests that someone has intentionally "cursed" the victim. A better understanding of the term "evil eye" can be gained from the old English word for casting the evil eye, namely "overlooking," implying that the gaze has remained focused on the coveted object, person, or animal for too long.

While some cultures hold that the evil eye is an involuntary jinx cast unintentionally by people unlucky enough to be cursed with the power to bestow it by their gaze, others hold that, while perhaps not strictly voluntary, the power is called forth by the sin of envy. In Jewish religious thought, it is sometimes asserted that the one who looks upon another with envy is not always at fault, but that the envy may be perceived by God, who then may redress the balance between two people by bringing the higher one low. It has been suggested that the term covet (to eye enviously) in the tenth Commandment refers to casting the evil eye, rather than to simply desire or envy.

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Belief in the evil eye is strongest in the Middle East, East and West Africa, South Asia, Central Asia and Europe, especially the Mediterranean region; it has also spread to other areas, including northern Europe, particularly in the Celtic regions, and the Americas, where it was brought by European colonists and Middle Eastern immigrants.

Belief in the evil eye is found in Islamic doctrine, based upon the verse of the Qur'an, "And from the evil of the envier when he envies," [Chapter al-Falaq, verse 5]and the statement of Prophet Muhammad, "The influence of an evil eye is a fact..." [Sahih Muslim, Book 26, Number 5427]. Authentic practices of warding off the evil eye are also commonly practiced by Muslims: rather than directly expressing appreciation of, for example, a child's beauty, it is customary to say Masha'Allah, that is, "God has willed it", or invoking God's blessings upon the object or person that is being admired. Aside from beliefs based upon authentic Islamic texts, a number of unsubstantiated beliefs about the evil eye are found in folk religion, typically revolving around the use of amulets or talismans as a means of protection.

Although the concept of cursing by staring or gazing is largely absent in East Asian and Southeast Asian societies, the Usog curse of the Philippines is an exception.

The oldest instance of belief in the evil eye dates back to biblical Israel. There are many instances of people casting the evil eye in both the Tanakh and the Talmud. Ashkenazi Jews in Europe and the Americas routinely exclaim Keyn aynhoreh! (also spelled Kein ayin hara!), meaning "No evil eye!" in Yiddish, to ward off a jinx after something or someone has been rashly praised or good news has been spoken aloud.

In the Aegean region and other areas where light-colored eyes are relatively rare, people with green eyes are thought to bestow the curse, intentionally or unintentionally. This belief may have arisen because people from cultures unused to the evil eye, such as Northern Europe, are likely to transgress local customs against staring or praising the beauty of children. Thus, in Greece and Turkey amulets against the evil eye take the form of blue eyes, and in the painting by John Phillip, above, we witness the culture-clash experienced by a woman who suspects that the artist's gaze implies that he is looking at her with the evil eye.

Attempts to ward off the curse of the evil eye have resulted in a number of talismans in many cultures. As a class, they are called "apotropaic" (Greek for "prophylactic" or "protective", literally: "turns away") talismans, meaning that they turn away or turn back harm.

Disks or balls, consisting of concentric blue and white circles (usually, from inside to outside, dark blue, light blue, white, dark blue) representing an evil eye are common apotropaic talismans in the Middle East, found on the prows of Mediterranean boats and elsewhere; in some forms of the folklore, the staring eyes are supposed to bend the malicious gaze back to the sorcerer.

Known as nazar (Turkish: nazar boncuğu or nazarlık), this talisman is the most frequently seen in Turkey, found in or on houses and vehicles or worn as beads.

A blue eye can also be found on some forms of the hamsa hand, an apotropaic hand-shaped amulet against the evil eye found in the Middle East. The word hamsa, also spelled khamsa and hamesh, means "five" referring to the fingers of the hand. In Jewish culture, the hamsa is called the Hand of Miriam; in Muslim culture, the Hand of Fatima.