Tradition of "Hi"

Why say "Hi"?

Sometimes, it's used to notify someone of your presence, if they haven't noticed you approach. But in situations where your presence is already implied -- like online, in a shared house, or outside when someone had noticed you -- why waste the time with this fluff word when you could go straight into substance? Even worse: if you had something to say, and your attention is redirected into greetings, you risk forgetting it or getting side-tracked with smalltalk. (And if you didn't have something to say, why greet at all?)

What is the point of the tradition of saying "Hello"? Is it a mere social tic? Is it rational?

Greetings establish or clarify context.

Greetings give information like:

• The mood of the other person. (Are they having a bad day? Are they tired and may be slow to react? Are they happy and want to see smiles?)
• How friendly the other person is feeling towards you. (A curt "Hi." vs a cheery "hiii" can give a lot of information about what kind of interaction to expect.)
• Expected level of politeness and intimacy. ("Hello" or "Good afternoon" may imply formality or seriousness; "Hey" or "yo" may imply lack of seriousness and/or more familiarity.)
• How much interaction they want. (An excited, engrossed "Hi!" may mean they want more interaction, compared to a quick, expectant "Hey?")

Greetings also give time to pick up other, more subtle bits of information. The way someone greets can reveal a lot of information about what they're thinking, what they want, what their background is. (If you doubt this, try walking through a street with charity fundraisers. Marketers can often be detected on the phone by greeting alone.)

When greetings are unnecessary

Online, the amount of context you need is greatly reduced. 

The reason is that text is anonymizing. You could have just got out of bed, you could have lost your voice from a cold, you could be between sobs following a breakup, you could be naked or in a tux for a ball, you could have friends over. In person, such things would need to be mentioned or addressed before you could go on with the interaction. ("What's up with the tuxedo?", "I just had a breakup so I'm a bit shakey but I'm OK to chat", etc.) But online, you can have a conversation without needing to clarify whether such bits of information you're leaking are relevant to the interaction.

In person, there is a jump from the previous context -- with all the information that comes with it -- and the new context of interaction. Greetings are partly a way of separating that out, clarifying which contextual information is relevant, and establishing a new context for interaction.

Online, that jump is smaller. There is less irrelevant context to sort through. The context of each person's life details are more hidden. Explicit context takes centre stage.

The jump is smaller and less context is needed. Not only that, but greetings in text loose a lot of their information -- tone of voice, body language, expression and other visual clues are gone. Online greetings can't pull the same weight as their in-person counterparts. So they are both less useful and less often needed.

When greetings are more necessary than you might think

Suppose you know someone well. You know a lot about their context. Maybe they're a significant other, or a sibling, or a flatmate. Maybe you live together or chat daily. You know what they've been up to lately, you can quickly read their mood and have a sense of what kind of interaction they might be up for. What can a greeting tell you that you don't already know?

Greetings are part of getting into sync, to embark on an interaction together.

If you skip the 'getting into sync' phase, you set yourself up for an awkward interaction. You may miss some key bits of information for making it go smoothly and being on the same page.

This is the case even if you already know the person. You don't always know everything that's been going on in their lives or minds. Even with a close significant other, something could have happened between now and when you last saw them. And sometimes, people need some buffer time between what they were just thinking about and interaction. Saying "Hi" is like saying, "I'm now paying attention to you and am ready to interact".

It may also have psychological benefits: it is a ritual to reassure each person that the interaction is safe, that you don't have to be worried about distractions, and that the interaction is a mutual agreement. 

The book Wired for Love describes "launching" and "landing" rituals: couples "launch" each other into the world (ready to take on the sometimes-uncomfortable outer world) using a parting ritual, and when they "land", it's like a return to home, greeting and receiving each other after being away. These rituals, the book argues, are important for couples to feel happy and secure in their relationship and in the world. It could be argued that the book portrays the outside world as a harsh place compared to the 'home' of the couple bubble -- which one may or may not agree with -- but the metaphor of launching and landing still conveys some of the inexplicit value of greetings.

VERDICT: Rational.