You spot the shortest supermarket queue, confidently wheel your trolley over and settle in. 

Within seconds, the line next to you starts flying. Another shopper who arrived after you is already leaving with their groceries, while you're still waiting behind someone searching for the right loyalty card.

It feels like a universal law of life.

But according to psychologists, mathematicians and queueing researchers, there are good reasons why it seems like we always end up in the slowest line, and surprisingly, it isn't just bad luck.

Your brain remembers the frustrating moments

One of the biggest reasons is how human memory works.

Psychologists say our brains are naturally wired to remember frustrating or negative experiences more strongly than ordinary ones. Standing in a queue that barely moves is emotionally irritating, making the experience far more memorable than the many times your chosen line moved quickly.

This creates what's known as confirmation bias. Over time, we begin to believe we're always unlucky because our brain keeps replaying the occasions when we were stuck waiting, while quietly forgetting all the successful choices.

Researchers also describe an illusory correlation, where people mistakenly connect two unrelated events, in this case, choosing a queue and it turning out to be slow. The more often we notice this coincidence, the more convinced we become that it happens every time.

The maths isn't on your side either

Even if every checkout is operating normally, probability works against you.

Imagine there are three queues. You only have a one-in-three chance of selecting the fastest one. That means there's a two-in-three chance that at least one other queue will move faster than yours.

So if another line appears to be overtaking yours, statistics suggest that's actually the more likely outcome.

Queueing theory, a branch of mathematics developed to study waiting lines, shows that small random delays can dramatically affect how quickly a queue moves. A single customer needing a price check, paying with multiple vouchers or having dozens of items can slow everyone behind them.

Meanwhile, another queue may consist entirely of customers buying just a handful of products, allowing it to move rapidly despite appearing longer.

Length doesn't always mean speed

Many shoppers instinctively choose the shortest queue.

Researchers say that's often the wrong metric.

What really determines waiting time is the amount of work waiting at the checkout, not simply the number of people.

Five customers carrying a basket each may finish much sooner than two customers with overflowing trolleys, complicated returns or payment issues.

Because these delays are impossible to predict, choosing the "best" queue becomes largely a matter of chance.

Switching queues often makes things feel worse

Almost everyone has experienced abandoning one line only to watch it suddenly speed up.

This happens because the queue you leave becomes the one you're now watching most closely.

Once you've switched, every customer moving through your old line feels like evidence that you've made the wrong decision, even if the overall waiting time ends up being nearly identical.

Psychologists say this heightened attention exaggerates the feeling that you've lost out.

Why one long queue usually works better

This is why airports, banks and many modern retailers increasingly favour a single winding queue feeding multiple counters.

Instead of each checkout having its own line, customers join one shared queue and move to whichever cashier becomes available first.

Queueing researchers say this system is generally more efficient because unexpected delays at one checkout no longer trap an entire group of customers. Instead, the delay is shared across everyone waiting, reducing the chance that one unlucky shopper bears the full impact.

Interestingly, studies have also found that people don't always like these systems. Even when a single queue gets customers through faster overall, many still prefer multiple lines because they enjoy the feeling of having control over their choice.

So, is the universe really against you?

Probably not.

The next time another queue seems to race ahead, remember that mathematics says it probably would. Your brain is also paying far more attention to the frustrating experience than to the countless ordinary ones you've already forgotten.

So while it may feel like the slowest queue has your name on it, science suggests you're simply experiencing a combination of probability, unpredictable delays and a brain that's especially good at remembering life's little annoyances.