There's ample evidence that eye contact is highly compelling: We're more attuned to faces whose eyes are trained on us than faces whose eyes are looking elsewhere. Even newborns pay more attention to faces with eyes gazing directly at them than to faces with eyes looking off in the distance.
You probably already know this if you've tried to read in a coffee shop and suddenly "felt" the stare of a stranger. (You look up, look back at them, and they usually look away. Unless they're trying to hit on you, in which case they ask what you're reading, whether you come here often, what you're drinking, or where you're headed next, and you spend the next 45 minutes trying to end the conversation so you can finish that chapter.)
The impact of someone else's eyes can work for or against our ability to stay focused. In many cases, us-directed gazes boost our ability to process information related to faces (i.e., concluding that a person is male or female) and enhance our memories of whoever was looking at us. Eye contact can also improve learning in general: A classic 1980 study by James P. Otteson and colleagues in found that young students whose teachers made eye contact with them during lectures had improved recall of verbal material after the class.
However, when we're trying to focus on something other than a person's face or the information they're trying to deliver, eye contact can distract us from non-facial information processing tasks (like that book you were trying to read).
Other people's eyes also affect our self-awareness: Several studies demonstrate that feeling looked at inclines people to become more attuned to their own body's physiological responses (heart rate, sweating, and breathing) as well as how they might be perceived by others (e.g., "Does s/he notice I have a toothpaste stain on my t-shirt?"). Mere images of eyes (paintings or pictures rather than an actual person) have even been found to make us act in a prosocial or reputable manner—and such images trump reminders that peers are present and/or will be judging us.
Additionally, we like people (and animated characters) more when these others appear to engage us through eye contact—provided the eye contact is offered in a non-threatening situation. Being gazed at by a potential mate has also been found to increase our attraction to them, as long as that potential mate also looks relatively happy.
In a recent review of the many powerful effects eye contact has on our behavior, cognition, and arousal levels, researchers Laurence Conty, Nathalie George, and Jari K. Hietanen explain that "direct gaze has the power to enhance the experience that the information present in the situation is strongly related to one's own person." They believe that the self-referential information processing brought about by feeling looked at "acts as an associative 'glue' for perception, memory, and decision-making." This can serve to enhance memory and make us behave more altruistically, they explain, by heightening "the salience of concerns about being a target for others' social evaluation and, consequently, concerns about one's self-reputation." (We do the right thing because we assume we're going to be judged, we're being watched, or we just like the person whose gaze looks warm, and we'd like to be nice to them out of sheer gratitude for being favorably noticed.)
The researchers believe that eye contact can and should be used "for therapeutic purposes." They note "that the use of eye contact during therapeutic processes increase the patient’s appraisal of the therapist’s interpersonal skills and effectiveness." Given eye contact's ability to enhance memory for specific context-specific material, they have a hunch eye contact may be particularly helpful for people with Alzheimer's Disease (AD), which, they write, "is characterized not only by memory impairments, but also by psycho-behavioral anomalies that necessarily appear at some point of the disease and impoverish the patient’s relations with others. Interestingly, the processing of eye direction as well as eye contact behavior seems to be preserved in patients with AD. This predicts that the W.E. [Watching Eyes] effects may also be preserved and may therefore be stimulated to improve the quality of social exchange of these patients."
Precautions should be observed, however, in subjecting people with certain diagnoses to excessive eye contact. The gaze of others can trigger intense feelings of shame and other negative self-evaluations in socially anxious individuals, for instance. And people who meet the criteria for borderline personality disorder are more apt to perceive negative emotions in others' facial expressions, potentially inclining them to interpret a kind or innocuous gaze as a threatening (or judgmental) stare.
Additional work suggests that when being confronted or challenged by someone, eye contact can serve to enhance perceived aggression. In fact, a study investigating the role of eye contact in persuasion found that direct gazes impaired actors' ability to change others' opinions, contrary to the assumption that eye contact always works in favor of increasing warm feelings between two people.
Research has shown that most people are comfortable with approximately 3.2 seconds of eye contact from a stranger—but more if that stranger seems trustworthy, and even more if that stranger later becomes a friend.
Eye contact can have a memory-boosting, prosocial, and stimulating effect as long as it's wanted by the person being looked at. If you're trying to use eye contact to your advantage, pay attention to the cues coming from the person you're staring at: If they're returning your gaze, lighting up, becoming more talkative, or straightening their posture or relaxing as you look into their eyes, you're doing great. But if they're shying away, acting nervous, looking annoyed, or they keep trying to turn their attention back toward the book you just distracted them from reading, it's probably a good idea to look (and possibly, go) away.