Brain training is based on the premise that mental stimulation can improve neuroplasticity. This is the brain's ability to form and reorganize connections between brain cells in response to new tasks.
While some studies have failed to find a link between brain training and improved cognitive functioning, other research has found the opposite.
A study published in PLOS One in 2013, for example, found that young adults who engaged in brain training games demonstrated improvements in brain processing speed, working memory, and executive functions.
It is not only young adults who might benefit from brain training. Research presented at the 2016 Alzheimer's Association International Conference found that older adults who took part in ten 1-hour brain training sessions over a 5-week period were 48 percent less likely to develop cognitive decline or dementia over 10 years.
Such studies have fueled the development of hundreds of brain training apps, many of which claim to improve cognitive functions such as learning, memory, and concentration. With so many to choose from, however, how do you know which one is best for you?
Medical News Today have tried and tested five of the best brain training apps available to help you make an informed decision.
Lumosity: Colorful and fun
Considered by many as the "original" brain training app, Lumosity is used by more than 85 million people across the globe. The app consists of more than 50 colorful and fun minigames designed to train five cognitive functions: speed, memory, attention, flexibility, and problem-solving.
Lumosity's games have been created with the help of more than 100 researchers from around the world. Furthermore, their website cites a study of more than 4,700 adults that found that brain training with Lumosity improved cognition more than crosswords.
With this in mind, we couldn't pass up the opportunity to try the app for ourselves.
At sign-up, you are required to complete a "fit test," which calibrates your speed, attention, and memory through three separate games.
Once the games are complete, users are shown how their results compare with those of other users in the same age group. This provides insight into the areas of cognition that require the most attention.
Each day going forward, Lumosity sends a reminder to complete a brain "workout." The daily brain workout involves playing three minigames - five with the premium version - each focusing on the five cognitive functions.
One game we enjoyed was Train of Thought, which focuses on attention. In this game, the user must change the direction of train tracks, with the aim of guiding different colored trains to the correct home. We found that this game really challenged our concentration - although it could be frustrating at times.
Luminosity is an app that could easily appeal to both children and adults. Many of the games - such as Highway Hazards, a driving game that involves moving left or right to avoid road hazards - have a child-like appeal.
Elevate: Boosting 'productivity, earning power, and self-confidence'
While Elevate has fewer users than Lumosity, at 10 million downloads worldwide, it holds the title of iPhone's best app of the year for 2014. So what makes it stand out?
The app consists of more than 40 minigames designed to boost math and speaking skills, as well as improve memory, attention, and processing speed.
According to the app's creators, "the more you train with Elevate, the more you'll improve critical cognitive skills that are designed to boost productivity, earning power, and self-confidence."
Just like Lumosity, Elevate encourages daily brain training, which involves the completion of three games, or five games with the "PRO" version.
Elevate has more of an adult feel than many of the other brain training apps; the minigames take a more serious approach, focusing less on colorful illustrations and more on text. Each game also comes with a brief description of its goal, such as "stop mixing up commonly confused words" and "improve your reading comprehension."
One game we enjoyed was Error Avoidance, whereby the user is required to "keep" or "swap" two words in a passage of text within a set time. For example: "He fashioned the cookie doe into the shape of a grazing dough." In this case, the two words would be swapped.
Elevate provides a daily, weekly, and monthly rundown of overall performance, as well as performance in five specific areas: writing, listening, speaking, reading, and math. If you're feeling competitive, you have the option of comparing your performance with that of other users in the same age group.
Peak: Flexible training and tracking
Rated by Google as one of the best Android apps for 2016, Peak offers more than 30 minigames to help improve concentration, memory, mental agility, language, and problem-solving.
These games have been developed with the help of scientists from respectable universities across the globe, including Yale University in Connecticut and the University of Cambridge in the United Kingdom.
Like Lumosity, there are a number of games that may appeal to children and adults alike. One such game is Turtle Traffic - a mental agility game that requires the user to navigate a turtle through the sea and collect jellyfish.
Based on performance in baseline tests, a personalized workout plan is provided, although the user is not limited to this plan. In the "Pro" version, all games are available to play at any time.
The Peak creators recommend brain training for 3 days per week. One great feature of Peak is that you can select the days that you want to train and set reminders for these days.
Cognitive performance is also very easy to track. Not only does the app provide information on individual game performance, but it also provides data on overall performance in each of the five cognitive functions. Similar to the other brain training apps, you are also able to compare performance with other users.
Fit Brains: Targeting emotional intelligence
Fit Brains is a creation of Rosetta Stone - an education technology software company best known for their online language courses.
This brain training app boasts the largest variety, with more than 60 minigames and more than 500 personalized training programs. With the input of neuroscientists, these games have been created to help exercise key cognitive functions, including concentration, memory, speed of thinking, and problem-solving.
What sets Fit Brains apart from other brain training apps, however, is that it also targets emotional intelligence through games that focus on social skills, social awareness, self-awareness, and self-control.
One game we enjoyed at MNT was Speedy Sorts - a game that tests thinking speed by asking the user to arrange objects into the correct piles as quickly as possible.
Based on the results of each game played, the user is provided with a score out of 200 for each cognitive area. The app also compares individual results with those of other users.
Unlike many other brain training apps, Fit Brains also has a school edition - a brain training package that aims to boost the cognitive functions of schoolchildren.
CogniFit: For consumers, scientists, and clinicians
CogniFit is perhaps the most advanced brain training app we reviewed, consisting of a variety of minigames designed to train more than 20 cognitive skills, including short-term memory, planning, hand-eye coordination, and auditory perception.
The CogniFit developers are keen to point out that all of their brain training tools have been validated by scientists - including researchers from the University of Washington and the Albert Einstein College of Medicine in New York. Furthermore, they state that the efficacy of their tools has been established through general population studies.
MNT tested the brain training games for consumers, and we found them to be a good balance of fun and mental stimulation.
One game we enjoyed was Reaction Field, which tests response time, visual scanning, and inhibition - which is the ability to control impulsive behavior. This game is similar to Whac-a-Mole; the user is required to remember the color of a mole and tap on moles of the same color as they pop up from holes in the ground.
Individual cognitive performance is assessed using the Lumosity Performance Index, which is calculated using the average scores of all games played. Like the other brain training apps, you can also compare your performance against that of other users.