Usability of websites may ascribe to the ease in which visitors can navigate and find helpful information through website pages and perform tasks successfully on the website; the visual design of webpages can determine the ease, convenience, as well as pleasure, of reading text, viewing images, interacting, and getting overall self-oriented on each page visited. However, as good as usability can get, it will not be enough if the visitor perceives the topic and context of a website to be of little relevance or interest. If the visitor cannot find a purpose to browse a website, testing for its usability to that visitor would be quite meaningless.

This position, in so many words, has been made by Eric Schaffer, CEO and founder of Human Factors International (HFI), a firm specialised in design practice, training and research. Eleven years ago (Sept. 2008) he published a white paper at HFI titled: “Beyond Usability: Designing for Persuasion, Emotion and Trust” (‘PET Design’ — HFI’s trademark).  The white paper describes a guiding framework and methodology for the design of websites that is driven by three fundamental psychological concepts involved in shaping and influencing human (consumer) behaviour. It is brought here to attention because the thinking behind this framework is compelling and may have come before its time. Schaffer suggested PET Design as the fourth wave of the Information Age (following hardware, software, and usability), and argued that a website cannot be effective and engaging without designing for persuasion, emotion and trust.

Persuasion is assigned with providing purpose. A visitor should be persuaded, for instance, that he may find on the website an answer (e.g., product, service, information) to a problem he needs to solve or a task to accomplish. In order for the prospect visitor-customer to ‘hire’ the website (following the “Theory of Jobs to Be Done” by Clayton Christensen), he or she has to be in a struggle at first — for example, resolving a new and unfamiliar situation or replacing a current solution (product) that is no longer satisfactory or not fitting a changed circumstance; then he or she should come to believe that the website holds the answer. Schaffer advises conducting a research prior to design of the preferences and decision making of potential users, their deeper drives and beliefs, as well as factors that may block them from doing things.

On the route to persuasion, however, an emotional ‘push’ may be needed. The design (structure, appearance) has to be not only persuasive but also engaging, to which an emotional drive would be more appropriate (e.g., fun, excitement and thrill, hope). Schaffer suggests that designing for an emotional reaction to an appropriate extent helps in persuading someone to make a decision, and optimises engagement.

  • Schaffer suggests that in some cases, to persuade visitors that the website is effective and to make it feel more engaging (e.g., increase interactions), the design should be kept as simple as possible (perhaps ‘too simple’); yet if the objective is to promote a sense of discovery and achievement, the design may include some complications or hurdles in purpose to challenge users.

Persuasion and emotion may not do without building trust. Measures to build trust through design have to be introduced pro-actively (Schaffer claims that HFI discovered variables that were most significant in driving trust in an online environment).  At the time, it was recognised, based on research, that FAQs are effective in establishing trust, demonstrating that the website owner is a ‘solid and diligent enough enterprise’ to document such information (note: today new interactive facilities may be more effective for developing trust, but that may not apply to IVA/chatbots). Another way of earning the trust of the user-customer is by providing a piece of information that the he or she can confirm or validate based on the individual’s prior knowledge.

HFI lists on its website an updated set of PET Tools (latest version 3.0 viewed Sept. 2019, see frame on the course page for PET Design). The set is composed of three main groups according to the model: Persuasion, Emotion, and Trust, plus a small subset for Navigation. The toolset refers designers to multiple behavioural, cognitive and emotional effects as well as phenomena that they should take account of in their planning and implementation work. Under Trust, for example, HFI includes aspects of reputation and good design next to ‘fine print’ (e.g., policies, sources of information) and the tone used. It is notable that the toolset itself does not relate directly to elements and figures of visual design — those are implicit or possibly derived as part of the implementation process.

The focus of Schaffer is on application of PET Design to websites, but this conceptual framework remains relevant also to certain types of software (e.g., learning, leisure and entertainment), and should furthermore be applicable today to mobile apps. Nevertheless, the psychological-oriented approach of PET can be beneficial also in the design of physical products such as home appliances and technological devices (many of which now entail software embedded in them). We may remind ourselves that websites (e.g., e-commerce) are frequently a channel or a gateway to tangible and intangible products consumers seek to hire to fulfill their task (or job). Regrettably, and rather strangely, the page on training for design of physical products, devices and tools, makes no mention of the PET Design framework and methodology.

One does not have to accept the line of reasoning used by Schaffer in full; parts of it seem somewhat over-stretched, such as on neuroscience and emotions. His white paper is not presenting a sound theory but a concept for practice. More crucially, the valued contribution of the approach taken by Schaffer and HFI is in application of concepts of persuasion, emotion and trust to the design of websites, with additional extensions conceivable. The relevance and importance of this conceptual framework to the process and outcome of design seems only to increase over time and to these days.



On the Theory of Jobs to Be Done, see: “Competing Against Luck: The Story of Innovation and Customer Choice“; Clayton M. Christensen with Taddy Hall, Karen Dillon. & David S. Duncan, 2016; Harper Business

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