We’ve all done it: grazed through our Facebook newsfeeds and impulsively hit the like button.

But beyond the fact that it’s so easy to use, what exactly is it that we find so irresistible about this tiny, seemingly innocuous function? And why are we so compelled to like people, updates and media online?

According to Facebook, a like is “a way to give positive feedback or to connect with people you care about.” The social-media giant recently released statistics indicating that more than 65 million users like things daily, and although it’s generally more popular among younger users, people of all ages seem to enjoy pressing the like button.

The fact that it’s such a popular element of the platform’s functionality goes a long way in showing how important it is, both for the people clicking the button, and those on the receiving end.

What lies behind our obsession with likes?

Like has become much more than just a positive reaction toward a post or update -- it has evolved into feedback toward people. As a rule of thumb, the more likes you get, the more loved you’ll feel. In fact, according to anthropologist Krystal D'Costa, the like button has become so influential as a tool that it can boost or shatter a person's ego. In effect, it has become "an extension of one's digital personal."

Not only that, but other researchers have shown that like-based communication actually decreases the feeling of loneliness, as it conveys a sense of empathy and caring. From the sender's perspective, sending a like can have the same effect as smiling or saying a kind word to someone. It is basically a really easy, low-cost way to communicate positive feedback.

Related: The Psychology Behind Why We Like, Share and Comment on Facebook (Infographic)

So why do we like things? People send compliments on a daily basis for a whole range of reasons, including rather strategic ones such as wanting to appear nice, to "suck up" or to gain something in return ("You look so nice today … Can I borrow your car?").

Complimenting a person is literally priceless -- it doesn’t cost you anything and it can be accomplished with minimum effort. You don't even have to mean it. People love to receive compliments even if they are very much aware of its manipulative usage. In fact, taken to its extreme, paying a compliment is a "legitimate" opportunity to lie, which is something that people subconsciously tend to enjoy doing from time to time.

Apart from transmitting a positive signal, the act of liking something is evidence of existence in the online realm. Comments affiliated with the like actually constitute your reputation online, and liking the same things as others within our networks reaffirms our connection with the group by identifying points we hold in common. There is, of course, the hope that a favor will be reciprocated: "I liked your post, now you have to like mine."

In recent years, the opportunity to like something or somebody has spread outside the boundaries of Facebook to other sites. You can press like after reading a news report, purchasing an accessory or watching a movie. In these cases, liking something is an indication of the consumer's satisfaction with the product or content, in which the like becomes a way to communicate their views and thoughts to other virtual users that they’ve never met before.

Your likes reveal more about you than you think.

Aside from the positive psychological impact of the Facebook like, as a function, it’s certainly not without its issues. In the spring of 2013, research conducted by psychologists at Cambridge University blew the lid off how this easily accessible digital record of your behaviour can be used (ultimately without your consent) to extract sensitive personal information about you -- the kind of information that you might not even share with your closest friends.

In the study, over 58,000 volunteers consensually provided their Facebook likes, detailed demographic profiles and the results of several psychometric tests. Using logistic/linear regression, the researchers were able to predict individual psycho-demographic profiles simply from their likes.

In a nutshell, they found that your likes can reveal everything from your sexual orientation, personality traits and IQ, to your race, age and gender. They can predict your religious and political views, whether your parents are separated, how happy you are and even whether you use addictive substances.

The relationship between like and voice.

What drives people to like things outside the boundaries of Facebook’s walls if the action is not accompanied by a social reward?

Here, the answer lies in the concept of voice. Voice is the opportunity you have to present your opinions in the decision-making process, before a final decision is made. As such, it can enhance your sense of satisfaction with your decision, as well as the process that led to it. Voice is instrumental because it helps you to increase control over the decision-making process, which in turn leads to a better outcome.

Numerous studies conducted both in the lab and in natural settings have shown that having a sense of voice can deepen positive feelings, even when it has no direct impact on a decision.

Related: Are You an Empathetic or Analytical Thinker? Your Music Playlist May Hold the Answer.

One such study that was designed to observe the effects of voice on both the sender and receiver found that voice increased satisfaction because it heightened the perceived value of the interaction. The study simulated a negotiation in the context of resource allocation, in which one group of participants was given the opportunity to voice their opinions prior to the final decision, and the other group was not.

The results indicated that in comparison to a no-voice condition, the voice condition (which yielded the same negotiation results) increased satisfaction with the decision, and generated positive feelings towards the process in both the sender and the receiver. This is exactly what the like is all about -- it enhances satisfaction as it gives value to the whole engagement process.

Having a voice in the decision-making process has been found to enhance satisfaction on both sides -- the side that has the opportunity to voice an opinion (the sender), and the side who hears the voice (the receiver). Pressing like after engaging in a personal activity online (reading an article, purchasing an item, watching a movie) is a way of expressing your voice.

There are two levels to the relationship between like and voice: explicit and implicit. At the explicit level, people press like to voice their positive feedback. At the implicit level, the phenomenon relates to the subconscious level of behavior. People value voice because it suggests that their views are worthy and have a positive impact on their social status and self-worth. The opportunity to voice an opinion is interpreted as an expression of respect and appreciation, and thus creates positive feelings.

Why your site should feature a like button.

Clicking like after reading an article, for example, is similar to saying: "I read this article, and I liked it. I want to express my views on the matter because my opinion is worth mentioning."

The possibility of sharing your opinion online suggests that someone is interested in what you have to say, which in turn has a positive effect on your sense of self-worth. Moreover, it provides the website with a social context. Having the option to like something signals the presence of a real person on the other side, rather than just a virtual figure. The ability to talk back, send comments or share a link (all of which generate positive impact with minimum effort) has the same psychological effect, which is why an increasing number of websites are choosing to use this technique.

It is also possible to learn about the importance of voice from people’s reactions when there is no voice. The frustration effect refers to circumstances in which, despite the possibility for people express an opinion, the decision-maker does not take those opinions into consideration. In such cases, people typically end up feeling worse than they would have, had they not been asked to voice their opinions in the first place.

Another implication of the like is self-persuasion. Because our actions secretly influence our opinions, clicking like can encourage positive thoughts we might have towards a brand or person. Research has shown that after having people actively present persuasive arguments as part of role play, they tend to express positive views that support that argument. Asking someone to say something, even if it contradicts their own views and opinion, can secretly twist their beliefs into favoring what they are saying. Likewise, even if people are not fond of a particular post, object, person or view, the simple act of clicking like, even when done with no profound intention or conviction, can lead to a rationalization process that will subconsciously make them feel positively about that post, object, person, etc.

The like has become so much more than just a positive reaction we express towards something someone has posted or updated. This simple function has become an incredibly influential tool both for the sender and the receiver. Used in a positive way, it can promote self-esteem, self-worth, feelings of acceptance and online socialization.

Its significance stems from both social incentives, because like affects the way other people perceive us, and individual incentives, because it impacts how we feel about ourselves.

Related: The Hidden Tricks of Powerful Persuasion