Curious readers who start with the first chapter are introduced to a puzzle that seems trivial yet is such a mystery that science still doesn’t have a full answer to it. Namely, why is it that we can have a goal in mind, can know what needs to be done, can urgently want that it be done, and yet, fail to do it? In other words, what connects our knowledge and goals with our actions? The brain requires a way of linking even our simplest fantasies about what we want to do with the reality of doing it. This is the basic function served by cognitive control, and its implications might surprise you.Consider, for example, the case of patient EVR, who was reported in the literature by Paul Eslinger and Antonio Damasio. A brain tumor had necessitated the removal of a large portion of EVR’s frontal lobe, a part of the brain that is essential for cognitive control function. After his surgery, EVR’s clinical assessment came out quite positive. He aced the cognitive tests he was given, and based only on these, it appeared his cognitive function had not been impacted by his brain damage at all.But EVR’s life outside the clinic had taken a very different turn. Prior to EVR’s disease and surgery, he had been a successful accountant, who was well respected and active in his community. Within a few short years, however, he lost his job, his marriage, a second marriage, and his overall enterprise in life. He was unable to get much of anything done. He could articulate the goals for his actions, the things he wanted to do, but was unable to carry them out in an organized or meaningful way.In EVR’s case, we see the paradox of cognitive control. It’s not enough that we can know what we want to do or even that we can carry out simple tasks, like those tested in the clinic. We need a way to link our knowledge to our action. In our complex and busy worlds, our brain needs a system to organize our behavior in time and with open-ended goals. And it needs a way to stay on track. The chapter draws on this and other striking observations of patients who have lost cognitive control function along with other examples that have long made scientists curious. I hope it will intrigue readers, as well.Other readers might just jump to chapters on the topics that interest them from the outset. For example, the chapter on multitasking might be of interest to anyone living in our hectic digital world. That chapter explains why we are so bad at multitasking (and why we sometimes aren’t). Armed with this knowledge, it considers what this might mean for our everyday lives.Cognitive control is central to our lives, but there is little broad understanding of the science behind it. I hope that readers will be introduced to something they didn’t know before and will gain a better understanding of this core but unfamiliar cognitive function. Though On Task is not strictly a self-help book, readers may also be able to use this knowledge to help cognitive control in their own lives. Cognitive control is within our control, so to speak, and we can structure our lives and environment to help our cognitive control system.Further, there is a lot of misinformation out there about concepts like executive function and brain structures like the prefrontal cortex. I commonly see claims being made about executive function that are not well grounded in scientific evidence, particularly among groups known to need aid with their executive function, like children or older adults. This has resulted in confusions and some widely held misconceptions.Moreover, there are also a number of widely marketed cognitive training interventions that claim to improve cognitive control or executive function. I treat that topic directly in the book and suggest to readers ways that they can evaluate such claims for themselves.Having a firmer grasp of the science may help readers navigate these topics better when they encounter them in their everyday lives. More generally, this book presents a story about how scientists approach a perplexing scientific problem. I hope reading that captivating tale will contribute to promoting curiosity and an appreciation of science in the broader public.