Reasoning is the ability to manipulate information in your brain according to logical rules. Mental activities that determine if something is true or false, or that require paying close attention to one thing while ignoring others, rely on your reasoning ability.

Reasoning does not live in a single part of the brain. Rather, there are networks throughout your brain that are activated when you do tests that require a lot of reasoning ability. Functional brain imaging of volunteers performing BrainLabs tests has revealed where these networks are:

The blue regions that control reasoning are known as the inferior frontal sulcus (IFS), inferior parietal cortex (IPC), and the dorsal portion of the anterior cingulate cortex / presupplementary motor area (ACC/preSMA). As you can see, they are distinct from the red regions, which are the parts activated by the working memory domain.

Does it matter which parts of your brain improve reasoning performance if you're not a neuroscientist? Maybe not, but it helps to know that your performance on the tests relies on physical chunks inside your skull. And just like any other physical performance, such as that of your muscles, it can be measured and improved.

Domain scores are calculated based on more than one test, and each test may contribute to more than one domain score. Specifically, domain scores are a weighted sum of individual test scores.

Reasoning is important in a lot of mental tasks, so many test scores contribute to it:

These calculations are based on a large study with over 44,000 people that looked at how the tests relate to each other (see Hampshire et al., 2012, for more detail). Your reasoning domain score is in relation to the population, telling you approximately how many people scored lower than you within that domain.