Why Two Easy Tasks Can Make Your Brain Slow Down

Easy plus easy can still create a wait

Two tasks can each be easy and still slow you down when they arrive together. Even changing the rule for the next simple task can add a delay that neither task has on its own.

You do not need a huge workload for this to happen. Lab experiments find extra delays in small choices, including responses to signals and basic judgments about numbers or shapes.

7 · Is it odd or even?Odd

7 · Is it above or below five?Above

An illustration of changing rules, not a timed experiment or a score of your attention. Research sources.

What changed when the number stayed the same?

The rule for answering. Recognizing the number was not the whole task; you also needed to know which question to answer.

Sometimes the second response has to wait

Harold Pashler reviewed experiments in which people responded to separate signals. When the signals arrived close together, the response to the second became slower on average.

One leading explanation is a bottleneck in choosing what to do. Some processing can overlap, but selecting one response can leave the next choice waiting.

Think of a barista taking an order just as a timer sounds. Hearing each demand may be easy. Deciding and responding to both at nearly the same moment adds another problem.

In the lab, researchers could change the gap between the signals. They then measured how long the second response took. Small tasks let them see a delay that a whole busy shift would hide.

The important surprise is that an easy second task does not become free just because you understand it.

Sometimes the rule is the extra job

Now consider a different setup. You see a number and decide whether it is odd or even. Then you see another number. This time, you must decide whether it is above or below five.

The next number may be no harder to read. But before giving an answer, you need the right rule. “Odd” is not an answer to “above or below five?”

In task-switching studies, people tend to respond more slowly after a change than after a repeat. Joshua Rubinstein, David Meyer and Jeffrey Evans found larger switching costs with more complex rules. Cues about the next task reduced the costs.

The changed rule and the second signal are not the same problem. One is about moving between tasks. The other is about demands that overlap. Calling both “multitasking” can hide that difference.

These lab findings do not give a fixed daily time loss, or show that people cannot do anything at the same time. They establish delays under tested conditions. The exact mental steps behind those delays remain debated.

Notice what changes, not just how long you pause

If your day feels full of small jobs that somehow take too long, look at the transitions as well as the jobs. Are two things demanding an answer now, or must you keep changing what kind of answer you are looking for?

Grouping similar tasks is one idea to try. It reduces the need to change rules, instead of asking you to make the same switches with more willpower.

A pause can belong to the setup of the work, not just the speed of the person doing it.