Persuasive web design in e-commerce: "How to sell things and influence people"

Many of the techniques introduced in my first captology article are applicable to the design of ecommerce websites.  Unlike other websites which may have a diverse range of behaviours they want to encourage, ecommerce websites have a single objective -  to make you spend money! How does the role of money impact persuasive web design?

How much are your customers prepared to pay?

The internet is forcing many industries to reconsider their traditional business models.  Perhaps the most high profile industries to trial new business models are the music and newspaper sectors.

Many newspapers are trialling micro-payment models whereby users pay a small fee for viewing and reading content.

Spotify main screen with adverts displayed

Spotify main screen with adverts playing

Typically a user pays a flat fee to read a set number of articles a month. Spotify ( uses a premium (or “Freemium” to quote Chris Anderson of “The Long Tail” fame) model where a small percentage of users are wiling to pay £10 a month to listen to music without adverts.

How can I ensure I adopt a pricing structure that will persuade users to buy my services?  If someone is willing to pay £10 for no adverts, would they pay £12?  What is the ultimate persuasive price?


Pretty persuasive isn’t it?!  In his latest book, Free, Chris Anderson identified an interesting finding that he termed “The Penny Gap”.  “The Penny Gap” is the name given to the significant difference in customers that a website sees between giving something away for free and charging for it.

How many businesses sit around prior to the launch of their website debating “shall we charge £10 or £12 a month?”  Chris Anderson argues that differences in our perception of price are negligible until you reach zero.  When your price reaches zero your customer base explodes in comparison to even selling something for £0.01 (hense the term “The Penny Gap”).  It’s not a case of £10 versus £12.  It’s more a case of “something” versus “nothing”.  Why?

A typical check out process involves multiple steps, probably involving forms and registration.  Suffice to say when a financial component is introduced to a website it will in all likelihood:

  • Take you longer to complete your objective, for example buy that T-shirt;
  • Make your task more difficult, for example;  enter my credit card details.

In the language of psychologists, the introduction of a check out process on a website will increase the cognitive load on the user.  The greater the cognitive load the less likely a user is to complete a task on a website.  Think of those web analytic graphs that demonstrate the drop off points of users in a multi-step process.

A second key consideration with the introduction of a price is risk.  I am forcing a visitor to ask themselves “How much am I prepared to pay for this?” This is why Radiohead asking their fans to choose the price of their last album, “In Rainbows”, was so fascinating to watch!

When something is free its easy.  How many people have picked up a copy of Metro on the way to work?  What if the Metro cost £0.10p instead of nothing?  Suddenly, as well as the additional cognitive load (I now have to stop, find my wallet, take out the money, wait for my change and have a conversation – “Beautiful morning isn’t it”) I am also weighing up in my mind whether I think the Metro is worth £0.10p.  I am forced to make a decision.  I’m taking a risk.  If you are asking me to take a risk then you have to work that much harder to persuade me.  How can captology help?

Reducing Cognitive Load – “Keep it simple and quick”

There have been hundreds of articles written about designing multiple step processes (particularly form design).  I will not dwell on how to design a simple checkout process here. It is a well known fact (and yet a poorly understood skill) that designing usability into your checkout process will increase your revenue.

Cognitive load consists of both time and complexity.  In my previous article that reducing complexity is a core aspect of increasing the persuasiveness of a website.  If a simplified ecommerce website with a low cognitive load can be said to be more persuasive, how can captology resolve the issue of time?

The ultimate example of reducing cognitive load to zero has to be Amazon’s “Buy now with 1-Click”.  Once I have used Amazon once this simple (from the front end at least) design effectively reduces my cognitive load to zero!

I have previously talked about the “Kairos Principle” which suggests there are opportune moments in a user journey to present information.  On an ecommerce website we can take this principle a step further and discuss an appropriate point in time in the real world to present key information.

Imagine it is the run up to Christmas and you run a website that sells t-shirts.  Trouble is five days before Christmas it becomes too late for anyone to order any t-shirts because they won’t arrive in time.  Instead of seeing my sales decline in the run up to the holidays I alter my homepage to offer downloadable and printable gift certificates instead!  Clever alterations in my website’s design can be targeted at key moments in the real world to ensure my profits are not adversely affected by the postal service!  In essence this application of the “Kairos” principle also reduces cognitive load because the website aids the decision making of a user (“Crikey, its Christmas Eve what can I buy for Frank?”).

Reducing Risk – “Earn my trust”

If every online purchase is a potential risk, how can we persuade users that the risk is not as great as they may perceive?

There are numerous well documented design techniques for earning trust (and thus persuading people) on an ecommerce website.  Product comparison options on a website give us more information on the pro’s and con’s of a product thus allowing a more informed decision to be made.  Clear prominent pricing and removing “hidden costs” (think tax on airfares) reassure us that we aren’t being scammed.  Perhaps the most powerful and wide spread tool for earning trust and persuading a purchase is reviews.

It is a testament to our natural social instincts that reviews and recommendations have become common place on the majority of ecommerce websites.  When a website says something is great I expect it too because it’s trying to sell it to me!  However, when another human says something is good I’m receiving confirmation that something I suspect might be a worthwhile purchase is in fact the case.  Recommendations are a particularly powerful persuasive tool. As well as building a level of trust they can reduce complexity (and thus cognitive load) by reducing the number of purchasing options from which we might choose.

The mFlow music recommendation listings in a users inbox

mFlow's recommendation listings

A new music service (currently in beta testing) called mFlow ( is banking on the persuasiveness of recommendation.  mFlow’s premise revolves around “friends” recommending music to one another.  If I make a recommendation and my friend buys the track both me and the record label get paid.

The current mFlow business model pays customers approximately £0.16p for a successful recommendation.  Surely paying your customers is even more persuasive than the magic number zero!  It remains to be seen how successful this business model will prove.

A final concern relating to risk and purchasing online is security.  If the design of the website cannot reassure me that my payment method is secure I will not buy.  I don’t have this financial concern when something is free.


When designing a persuasive ecommerce website you need to consider two key factors: reduce the cognitive load of your users and reassure them that the level of risk associated with the purchase is low.

Both cognitive load and risk can be reduced through following a strategic user centred design process.  However, good design will only take us so far in our quest for the ultimate persuasive ecommerce website.

The business model that a company’s website adopts will naturally introduce a level of complexity that will immediately influence the persuasiveness of the website.  It is not unusual to hear of internet start ups claiming “It only costs $3 a month” and yet failing to see significant customer uptake.

I am not suggesting every business should give away its products or services for free.  My point is that the adoption of a certain business model will resonate throughout your design and will have a big impact on the persuasiveness of your ecommerce website (and ultimately performance and therefore revenues).

Before we begin to design our new ecommerce website have we considered the impact of our chosen business model?  Have we already inadvertently introduced an unacceptable level of complexity that the best design in the world will only mitigate and not remove?

What’s my point?

In my opinion, the application of captology within ecommerce is a full lifecycle activity that begins in the boardroom not the wireframe.  As usability and web design professionals can we help our clients to understand the impact that these very early business decisions can have?  I will explore this idea further in my next article.


1.  Chris Anderson.  Free: The Future of a Radical Price.  Hyperion Books. July 2009

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