There’s no way around it: methylphenidate - better known as Ritalin - is a stimulant in the same general category as cocaine. This leads to a seeming paradox: why would giving a stimulant to someone struggling with sustained attention help them to focus?

Although there continues to be much debate among researchers concerning the precise reasons for Ritalin’s beneficial impact, one compelling and likely mechanism concerns attention thresholds.

The world is an incredibly noisy place. All day we are constantly and continuously bombarded with sensations (visual, auditory, olfactory, etc). One method the brain has developed to sift through all this input is to generate a “threshold”. Simply put, in order for you to consciously pay attention to any incoming signal, that signal must be stronger than your threshold.

For instance, imagine if somebody near you began to shout. This strong signal would likely be larger than your threshold, meaning you could pay attention to it (if you chose).

Now imagine if a tiny mouse in the corner of the room sneezed. There would still be a signal, albeit an incredibly weak one, likely lower than your threshold. This means you don’t have the option to pay attention to it.

As we saw in an earlier column, one way to manipulate this system is to add random noise to a signal. This process (called stochastic resonance) can boost weak signals above a threshold, thereby allowing us to focus on them.

A second way to manipulate this system is to target the threshold directly. This is essentially what Ritalin, Adderall and other stimulants do. Largely via manipulating the neurotransmitter dopamine, these drugs serve to enhance brain-cell sensitivity, thereby lowering an individual’s attention threshold and allowing for more signals to enter into and be detectable by the system.

It is intuitive to assume that ADHD is characterised by individuals having a naturally low threshold; essentially, too many signals enter the system. In truth, it’s the exact opposite - many forms of ADHD are characterised by individuals having a naturally high threshold; very few signals enter the system. This scarcity leads to an inability to sustain focus (as signals don’t remain above threshold for very long) and rapid shifting (as attention quickly moves to whatever signal most recently jumped above threshold). Do you see the link?

When neurotypical individuals ingest Ritalin, it lowers their attention threshold leading to jitteriness, giddiness and hyperactivity due to too much incoming information. When some individuals with ADHD ingest Ritalin, it lowers their threshold in the same manner as everybody else - however, seeing as their threshold starts at a much higher level, this lowering simply “normalises” them, allowing sustained focus and concentration.

There are a couple of important caveats.

First, there are several different forms and/or causes of ADHD. As such, this mechanism cannot be considered universal.

Second, Ritalin may help some individuals focus, but this does not eliminate the need for motivation, effort, and effective teaching and learning. Just because a person can pay attention does not mean he/she will want to.

Finally, Ritalin is not essential. Via cognitive, behavioural and/or other lifestyle means, some individuals with ADHD can function comfortably (and effectively) without pharmacological intervention.

Jared Cooney Horvath is a neuroscientist, educator and author, and is director of the Science of Learning Group. He is an honorary research fellow at St Vincent’s Hospital and the Melbourne Graduate School of Education

Full references can be found at tes.com, and if you’d like to ask our resident learning scientist a question, email AskALearningScientist@gmail.com

This article originally appeared in the 29 November 2019 issue under the headline “Why would Ritalin (a stimulant) help students with ADHD concentrate?”