What becomes possible when something isn't the same?

Something changes. A sound is slightly different. One option costs less. Someone sees something you don't. An outcome isn't what you expected. Difference gives us something to work with. But a difference can exist without becoming available to you. The difference has to be perceived by the receiver.

Different from what?

Nothing is simply different. It is different relative to something else. A sound differs from the sound you expected. Today's result differs from yesterday's. A person's behaviour differs from what you've come to regard as normal. Option A differs from option B. This is why models of normal matter. To notice that something has changed, you need some representation against which the change can be perceived. Sometimes the comparison is obvious. Sometimes a difference catches you before you know what the comparison was: Something isn't quite right. The difference may reveal the normal you didn't know you were expecting.

Difference has to become available

Two signals can be different without the receiver being able to tell them apart. To one person: same. To another: different. The difference may be in the world. But whether it becomes available depends partly on the receiver. Experience can matter. Training can matter. Attention can matter. The model of normal can matter. And resolution can matter. A difference too fine for one receiver to perceive may be obvious to another. So an important question isn't only: Is there a difference? It is also: Can I perceive the difference?

Expertise can increase resolution

A novice hears an engine. An experienced mechanic hears that engine. A beginner watches a tennis serve. A coach sees the fractionally late movement that changed it. A new pilot sees an instrument reading. An experienced pilot sees that it isn't behaving quite as expected. Expertise can build richer models of normal against which increasingly fine differences can become available. What once looked the same becomes distinguishable. And that gives us an important possibility: Perhaps we can train ourselves to perceive useful differences that would previously have passed us by. Not every difference. Not maximum resolution. Useful resolution for the purpose.

Difference makes choice possible

Imagine two options: A or A. There is nothing to choose between. Now: A or B. Something differs. That difference gives the receiver a possible basis for comparison. Which is cheaper? Which is safer? Which is faster? Which do I prefer? Which is good enough? Which is better — according to the ruler I'm using? Without a perceived difference, there is no basis on which to prefer one identical representation over the other. Difference doesn't tell us which option to choose. It gives us something to judge.

Difference makes better possible

Suppose you do something one way. Then you try something slightly different. You judge the second version to be better. The improvement might be enormous. Or tiny. Either way, something had to differ. So: Difference makes BETTER possible. But difference also makes WORSE possible. And that's fine too. A worse result gives us something else to compare. What changed? Why was this worse? What might we do differently next time? Worse can provide information. Difference gives learning something to work with.

Other receivers give us difference

Difference isn't only between things. It can also exist between representations. You see one thing. I see another. Your experience makes something available to you that mine doesn't. My perspective gives me a different comparison. Neither of us necessarily has the complete representation. That can make difference uncomfortable. But it can also make another receiver extraordinarily valuable. You may see something I can't. A team of identical receivers, with identical models, identical resolution and identical perspectives, would have little difference to contribute to one another. Another receiver can give us something we couldn't generate alone.

Don't eliminate difference too quickly

We naturally try to resolve disagreement. Who's right? Which representation should we keep? Which option should we reject? Sometimes that is necessary. But difference itself may contain useful information. Before eliminating it, perhaps ask: Why do we see this differently? Different experience? Different information? Different model of normal? Different ruler? Different purpose? Different timescale? Different resolution? The disagreement may still need resolving. But first, it may deserve understanding.

Difference can change what matters

Not every difference deserves resources. Most don't. And which differences matter can change. A tiny change in an aircraft instrument may deserve immediate attention. A much larger difference elsewhere may deserve none. Change the environment and you may change which differences are consequential. What mattered yesterday may not matter today. What passed unnoticed yesterday may suddenly become important. So the task isn't: Notice every difference. We couldn't. It is closer to: Become capable of noticing useful differences — and get better at judging which deserve more.

Difference can change the receiver

You notice a difference. You explore it. Perhaps you learn something. Now you have a distinction you didn't have before. Something that previously looked: ‘same’ may forever afterwards look: ‘A / B’. Your resolution has changed. Your model of normal may have changed. And that means a finer difference may become available next time. So difference doesn't merely give us something to notice. Learning from difference can change what we become capable of noticing next.