How many psychologists does it take to change a light bulb? None, the light bulb has to want to change. So the joke goes. However, it's possible that the light bulb could be persuaded to change. Persuading people to buy online (from TVs to groceries, holidays to services) can be achieved with techniques that marketers and psychologists have known for years.

Persuasion isn't rocket science; it involves understanding aspects of human nature that are often automatic and work at a subconscious level. Here are 7 ethical ways to persuade people.

Online persuasion - 7 ways to persuade people to buy

How many psychologists does it take to change a light bulb? None, the light bulb has to want to change. So the joke goes. However, it's possible that the light bulb could be persuaded to change. Persuading people to buy online (from TVs to groceries, holidays to services) can be achieved with techniques that marketers and psychologists have known for years.

Persuasion isn't rocket science; it involves understanding aspects of human nature that are often automatic and work at a subconscious level. Here are 7 ethical ways to persuade people.

1. Show what others are doing

People look to others and will often do what they're doing, especially when uncertain about something. This psychological phenomenon is called social proof. People feel reassured and often make decisions based upon what other people are up to - the assumption being that they possess more knowledge or are better informed than they are.

You can increase social proof online by showing:

• Most popular items
• 'Customers who bought this also bought'
• Top sellers
• Testimonials

Additionally, people will do what people that they like do.

2. Show user-generated reviews

User-generated reviews can have a massive influence on peoples' buying decisions. Fuelled by the rapid growth of web 2.0 and social media they're becoming an essential part of website design. Allow your site users to write reviews and express overall ratings for products and services on your site - after all, it's free content for your site. Web users are more inclined to trust what people like themselves say, compared to marketers. Reviews are especially critical in sectors like travel and electrical goods, although they're rapidly being adopted across all areas.

People generally want user generated reviews and if they can't find them on your site, they'll simply look elsewhere. There's no hiding online so you might as well keep them on your site. Sites like Figleaves and the UK Apple store website understand this and implement them really well.

Also, don't be scared of bad reviews - people can smell sites that have been 'edited' a mile away, forcing them to simply not trust anything you say. Instead, be prepared to act quickly on your customers' feedback.

3. Show scarcity of products

Scarcity generates demand and encourages people to buy sooner. People want what they think they can't have and social psychology would indicate that loss is a more powerful emotion than gain. So, a person who loses $100 is estimated to lose around twice as much satisfaction as another person will gain from a $100 windfall.

You can show scarcity online by displaying:

• 'For 1 week only'
• '2 items in stock'
• 'Sale ends today'
• 'Out of stock - Add to wish list'
• 'This offer ends in 2 days 4 hrs 3 mins 17 secs' (Count down timers)

Webcredible shows the number of places remaining on training courses on its site. The numbers decrease daily until all places have gone, giving visitors a sense of urgency to book their place before it sells out. Research on decision-making also indicates that people value something more so if they felt they lost out on it, rather than if they never had it in the first place.