Perpetual motion machines do not exist

Robert Fludd’s description of a perpetual motion machine from the 17^th Century. The idea involved water held in a tank above the apparatus driving a water wheel which, through a complex set of gears, rotate an Archimedes screw which draws the water back up to the water tank.

 

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The idea of creating a machine which can continue indefinitely without any source of energy to power it is one that has fascinated inventors since the astronomer and mathematician Bhāskara II described a wheel which could run forever in the 12^th century. The failure to build such a machine hasn’t stopped people from trying to build them or even applications for patent; whether using magnets, or gravity or buoyancy as the basis for perpetual motion. However, no attempt to create one has ever worked.

Perpetual motion machines do not exist, because no one has built a machine which can continue indefinitely without some external source of energy to keep it going.

It would be very, very odd for someone to claim that they did exist, simply because inventors periodically try to create one. I’d certainly accept that they have tried to create a perpetual motion machine (and thus far failed), or created a machine which they claimed possessed perpetual motion (but didn’t really) – but to say that perpetual motion machines ‘exist’ surely implies that someone has built one that actually works.

I recently read a short series of blogs defending the idea of ‘learning styles’. The idea at the heart of learning styles is that information provided to a student in a form that matches their ‘style of learning’ will lead to improved learning.

Coffield et al (2004) review over a dozen attempts to measure differences in learning ability so that instruction can be matched to this ‘style of learning’. Certainly, all of the systems have tried to define learning styles, but the question is whether any of them actually work. They found that whilst a few of the them provided some relatively valid measures of differences between people, none of them demonstrated that attempting to match teaching to this style would have any benefit.

They conclude that whilst learning style theorists have conducted small-scale, weakly controlled studies to support their claims, none of them produce systems with any clear evidence that using them will advantage learners. None of the proposed systems work.

Pashler et al (2008) helpfully define what a learning style is supposed to be.

“The term ‘‘learning styles’’ refers to the concept that individuals differ in regard to what mode of instruction or study is most effective for them. Proponents of learning-style assessment contend that optimal instruction requires diagnosing individuals’ learning style and tailoring instruction accordingly.”

This makes it clear that merely identifying some differences in people isn’t sufficient for the label of a ‘learning style’ to be applied. As well as being able to measure some sort of psychometrically reliable differences, a learning style also needs to show what mode of instruction would be most effective for an individual. They also note that very few studies have actually tested whether proposed learning styles actually improve learning when instruction is tailored to them. Where these studies have been conducted, several found results which contradicted their claims. The data so far do not support the idea of learning styles.

No attempt at ‘learning styles’ has ever succeeded. It would seem bizarre, therefore, to claim that learning styles exist. I’d certainly accept that people have tried to describe learning styles (and failed) or that some people claim a system of learning styles is effective (when they don’t have evidence to support that view).

Cognitive scientists like Daniel Willingham and teachers like Tom Bennett seem on pretty safe ground making the claim that they don’t exist. The burden of proof is on those claiming that learning styles exist – let them produce the data showing both valid measures which differentiate learners and that matching instruction to these differences enhances learning. If robust evidence to support this comes to light in the future, then I am certain both would change their position (as would I) – that’s the nature of science.

In the meantime, however, claiming that ‘learning styles exist’ smacks almost of what Irving Langmuir called pathological science: ‘an area of research where “people are tricked into false results … by subjective effects, wishful thinking or threshold interactions”’. Langmuir identified pathological science, like perpetual motion machines, as fruitless ideas that simply will not “go away” despite repeated failure.

Given that attempts to identify effective learning styles is hardly new (at least since the 1980s), I have sympathy with the frustration in this article by Tom Bennett which argues that VAK – the most notorious attempt at learning styles in UK education –  is a ‘zombie’ idea in education that simply fails to die.