Alchemy and the role of logic in medical device design

13 Nov 2023 4min read

I recently discovered Rory Sutherland’s book Alchemy – and would recommend it to those interested in human behaviour. One of the key messages in the book is that logic isn’t always the best approach when dealing with human behaviour. To quote Sutherland: “Logic maybe the best way to succeed in an argument or a board meeting. But if you want to have an edge in business and in life, logic is not very useful. As much as economists would want us to believe, human beings don’t run on logic. They run on psycho-logic.”

The link between human factors and logic

As someone who works within human factors for medical device development, this message really resonates with me. It is a concept that can be applied to the design and development of medical devices, including labelling.

This is particularly true when considering how we approach the design of Instructions for Use (IFUs). In the medical device industry, IFUs do not always support a positive onboarding experience for users (e.g., patients and healthcare professionals). As heavily regulated documents, the design of IFUs is all too often constrained by logical thinking born out of risk analyses, precedents and guidance documents. The result is often an IFU that is comprehensive in information but overly detailed to the extent that the cognitive load placed upon the reader is significant. Not only does this reduce the effectiveness of the IFU to communicate the key use steps, it also creates a perception of device complexity that can lead to confusion and negatively impact the experience of interacting with a device for the first time.

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A fresh, logical perspective

If we wish to change this, then I believe manufacturers, designers and regulators of IFUs need to look at the problem from a different perspective. In Sutherland’s book, the simple lesson is this: a plausible ‘why’ should not always be a prerequisite in deciding a ‘what’ when it comes to dealing with human behaviour. A better approach is to try a few experiments, detect the patterns, understand the contexts in which they work, and apply ‘psycho-logic’.

Indeed, while IFUs have often been designed with logical thinking, this may not be the best approach for ensuring an effective, user-based design. In my experience, when it comes to IFU design and instructing well – that is to reduce cognitive load and provide a positive onboarding experience – I am a firm believer that less is more.

To demonstrate the effectiveness of this, it is helpful to set aside the known constraints and start experimenting with the impact of providing users with less information. When users engage with instructions for the first time, it is important to remember that they will have preconceptions about device use before they’ve read the first word of your IFU. Instructions should be designed with these user preconceptions in mind and make use of the users’ mental models and expectations, leveraging them when the device works in a similar way or emphasising key differences when a device works in a manner that contradicts a known affordance or user expectation.

When you experiment with providing users with less information in a manner that leverages existing mental models, you will quickly learn that users can ‘fill in the blanks’ and grasp the core use of a product with very few, well-considered words and illustrations.

Improving the medical device user experience

Of course, achieving this in the highly regulated world of medical device design will be no easy feat. Proposing a perceived “radical” approach, such as providing users with less information and a simplified message of device use that conveys the key use steps necessary to administer a dose, will inevitably come up against logical counter arguments at some point. When it does, we should keep in mind that simply taking the logical approach will make the outcome predictable and indeed similar to what already exists.

If we wish to make the experience better for users of medical devices, we need to be willing to challenge the conventional and logical approach to problem solving. This, of course, extends far beyond the design of IFUs and is an important point for medical device development in general.

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