Designing for Social Interaction

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It took both the telephone and the mobile phone 15 years to amass 100 million users, but Facebook did it in 9 months. We see more and more people becoming connected on online social networks, and it seems our networks are growing exponentially. But the reality is, social networks rarely add to our number of connections. We’ve already met almost all the people we’re connected to on social networks. We’re already connected to these people offline. Social networks simply make the connections visible. For example, we often connect with old school friends, and catch up over a couple of wall posts. But rarely do we continue the conversation once we’ve connected, and over time we forget that the connections exist. In fact, Facebook users often have no interactions with up to 50% of their connections.1 When we study how people are interacting on social networks, we see that most interactions are with a very small subset of the people we’re connected to.

The average number of friends on Facebook is 130, and many users have many more.2 Yet despite having hundreds of friends, most people on Facebook only interact regularly with 4 to 7 people,3 and for 90% of Facebook users, 20% of their friends account for 70% of all interactions.4 We also see this with phone usage. We have hundreds of people in our phone contacts, yet 80% of phone calls are made to the same 4 people. We know dozens of people who use Skype, yet 80% of Skype calls are made to 2 people.5 Even when people play computer games online, they mostly play with people they know offline.6

We also have varied interactions with the people we’re not as close to. We find out about new jobs, not through our friends, but through friends of friends. When our friends’ friends’ friends lose weight, we lose weight.7 We go onto eBay and buy things for hundreds and thousands of dollars from people we’ve never met, and will probably never interact with again.

We have many diverse relationships with the people in our lives, yet the web doesn’t support this very well.

the web doesn't support different layers of relationships very well

On Facebook (left), all my “friends” are treated equally. I’m presented with a long alphabetical list. Some of these people I would trust with my deepest secrets, and there are others that I’ve met less than five times. Yet they are grouped together in a big bucket of “friends”. Of the people who are “friends” with me on Facebook, there are many that I wouldn’t call a “friend”. I may call them an acquaintance, or a colleague, or even a family member, but they’re not in the same category as my closest friends.

In my phone (right), all my contacts are treated equally. I’m presented with a long alphabetical list. My best friend is given the same number of pixels as someone I haven’t spoken to in 5 years. I may be able to access my most frequently contacted people via a ‘Favorites’ tab, but these people are still presented in the same way as the people I’ve lost touch with. On LinkedIn (right), all my connections are treated equally. Yet I have worked with some of them every day for years, and there are others that I met once at a conference.

Our social web tools must start to understand the strength of ties, that we have stronger relationships with some people than with others. And with this knowledge they need to adapt.

There are three kinds of relationship ties:

  • Strong ties: People we care deeply about.
  • Weak ties: People we are loosely connected to, like friends of friends.
  • Temporary ties: People we don’t know, and interact with temporarily.

Let’s look at each type of tie, and how we might design for them.

Most people have less than 10 strong ties

For decades, people have talked about social networks being made up of strong and weak ties. Think of the people in your life. Think about your closest friends, the people you are closest to in your family. These are examples of your strong ties. Strong ties are the people you care about most. People often refer to strong ties as people in their “circle of trust”. Strong ties often wield the most influence over people‚Äôs decisions.

Most people have very few strong ties, usually less than ten. A study of 3000 randomly chosen Americans showed that the average American has just four close social contacts (four strong ties). Most Americans have between two and six strong ties. People’s strong ties come from a variety of places. About half of the strong ties are said to be friends. The other half includes spouses, partners, parents, siblings, children, co-workers, fellow members of clubs, neighbors, and professional advisors and consultants.8 In both 2002 and 2007, a study of 1,178 adults found that on average, people had about 10 friends they meet or speak with at least weekly (10 strong ties).9 So, when we’re designing for strong ties, we’re designing for small groups of people.

Some people believe that this is changing, that the web is making us closer to more people.10 On the contrary, research studies have shown that the vast majority of usage on social networks is between strong ties. As we saw earlier, on Facebook it’s with 4 to 6 people, with phone calls its with 4 people, and with Skype it’s 2 people. When people play online computer games with others, they are mostly interacting and playing with people they know, often with people who live less than a few miles away. This pattern of technology being used for strong tie communication is not new. When the telephone was invented, it did more to expand and strengthen strong ties than to weaken them. A study in the 1970s showed that the majority of phone calls were to people who live within five miles of the caller’s home.11

When designing for strong ties:

  • Think about their existing means of communication. Phone calls, text messages, email. Strong ties already have established ways to interact, we should support them, and not try and replace them with our own messaging systems.
  • Showing more information about the ten closest people is likely to be much more valuable than showing less information about many more people.
  • Avoid generic terms such as “Friends”. This will likely lead to over-populating groups and reducing their relevance.
  • Suggest connections to people, but communicate the effects of adding new connections.

People have about 150 weak ties that they stay up-to-date with

Moving away from your strongest ties, think about some of your friends’ friends. People you don’t know so well. These are examples of your weak ties. Weak ties are people you know, but care less about. These are the people that are loosely connected to you. Weak ties are people you wouldn’t feel uncomfortable stuck in a elevator with, yet don’t feel much emotional closeness to.

In the 1970s, the sociologist Marc Granovetter wrote a seminal paper about the strength of weak ties. He concluded that weak ties are often a much better source of information than strong ties. As our strong ties are a very small circle, weak ties can be a more powerful source of information and advice. Studies show that most people can only stay up-to-date with 150 weak ties in real life. This pattern has been true for thousands of years. Neolithic villages tended to separate into two once they reached 150 inhabitants, the Roman army was split into groups of 150, so that everyone knew each other.12 It is still true today, online and offline. We are connected to many more than 150 weak ties, but don’t stay in touch with them. We may be connected to hundreds of people on Facebook, but we would struggle to tell anyone what is going on in all of their lives.

In social networks, weak ties can sometimes be very useful, for example, connections on LinkedIn can help you find a new job, a friend of a friend can give you advice on a specific topic. Yet sometimes, weak ties on social networks can lead to awkward social situations, for example, receiving unwanted Facebook invites from people you don’t know very well.

When designing for weak ties:

  • Consider the trade-off between communication and trust. Weak ties may be more knowledgeable about something we’re interested in, but we may trust them less. It may be important to show our other shared ties, or expose their sources of knowledge, so that we can increase the trust between people.
  • Make it easy for people to expose their networks to people they trust with that data. This will open up links between weak ties, without compromising user privacy.
  • Enable appropriate communication channels between weak ties. It may be better to go through, or highlight, a shared strong tie.

The web is increasing our interactions with temporary ties

Strong and weak ties are not enough when we think of relationships online. We need a new category of tie – the temporary tie.

Temporary ties have always existed, but the web is bringing them to the fore. Think about some people you’ve only interacted with once. You don’t actually know who they are. A store assistant, a call center employee, the person you bought from on eBay. These are examples of your temporary ties. Temporary ties are much more common online than offline. They are people that you have no recognized relationship with, but temporarily interact with for a specific reason. Once the task has been completed, temporary ties are unlikely to interact again. You don’t know these people beyond the words they typed, and whatever online profile they have. With the rise of online user generated content, temporary ties are becoming more important.

Following are four common types of temporary ties:

  1. People sometimes interact with temporary ties around an information need. People needing information seek people with knowledge of the answer. Once the request for information has been fulfilled, interaction with these ties usually ceases. You may ask a person in the street for directions, or online you may seek information from people on Yahoo! Answers. This type of temporary tie is increasingly important for the future of web search. People are looking to other people, rather than businesses, to answer certain queries.
  2. Temporary ties also exist when people need to temporarily interact to complete a task. Once the task is completed, interaction ceases. For example, interacting with a sales assistant in a shop, or having a plumber in your house to fix a leaking pipe. Many of these tasks are now online, for example interacting with a call center representative to arrange cable installation, or buying something from a temporary tie on eBay.
  3. Temporary ties can form around a shared ongoing interest such as a sports team or hobby. Interaction can often happen on a community website, for example a sports team forum. The true identity of these ties can remain unknown. One some of these sites, frequent posters start to recognise each other and each other’s behaviour. Although they likely have never met, their relationship can move from temporary tie to weak tie. There are an increasing number of examples where temporary ties interact online, and meet offline.
  4. People often form temporary ties with people sharing the same physical space. These ties can be as simple as a 1 minute conversation on the street, or as complex as an intermittent 3 day conversation at a music festival. Technology now allows us to communicate with temporary ties who shared the same physical space with us, albeit not at the same time. We can use our phones to see who has previously been to the restaurant we’re considering, what they ordered, and whether they thought it was any good.

Because we have no relationship history with our temporary ties (unlike with our strong and weak ties), representing identity and reputation are critical for successful interactions. We need to know that the eBay seller is trustworthy. We need to know that the medical advice we’re reading is from an actual doctor, and not someone pretending that they are a doctor. We need to know that the restaurant review is from someone who knows about food, and that the Amazon review wasn’t written by a company employee.

reputation building

On Yahoo Answers, people can build their reputation in different ways. On the left, “Messykat” is building her reputation by trying to provide the best answers to questions. She may be helpful in 20% of cases, but we still don’t know much about her credentials as an expert in any of her 3 specialty areas (Cats, Dogs, Weddings). On the right, “RuthAnn” is trying to build her reputation by stating that she “has been training dogs for 40 years”. This only adds a superficial layer of credibility, as we can’t verify if it is true.

building trust by positive feedback from temporary ties

On eBay (left), “jmjenkins” is building trust by getting positive feedback from temporary ties who have dealt with him in the past. Some of these people have also left positive comments on his profile, e.g. “Item just as described, arrived safe and sound. Thanks! A++”.

On Amazon (right), “W.Todd Dominey” is building his reputation by providing helpful reviews in 665 of 711 cases. He is also building trust by using his real name, and sharing where he is from. However, as with “RuthAnn” on Yahoo Answers, we don’t know how much “W.Todd Dominey” knows about the topic being reviewed. We can’t verify his credentials.

The motivation for most people who help their temporary ties is not monetary. You can’t create a great temporary tie community with financial reward. Yelp tried to do this by paying people $1 per review, and later they tried to build communities by paying people $15 an hour to comment on existing reviews and write new ones. Yelp ended up with a lot of poor quality reviews 13 14, and a lot of bad press. Some of the actual motivations for temporary ties include recognition of being an expert, altruism, and feeling that they belong to a community. All of these behaviors need to be understood and accounted for in our social web designs.

Supporting temporary ties is good for business. One study showed evidence that “an increase in positive comments about a mobile handset typically appeared a month or two before an increase in market share for that handset.”15 Another study over 7 months showed that when the online promoter activity (an estimate of the online chatter likely to lead to a recommendation) went up, sales went up the following month. When activity went down, sales went down. 16

When designing for temporary ties:

  • Prioritize a great system for building reputation. Allow people to give feedback to one another.
  • Encourage people to expose content that will increase trust in their identity. This could be their real name, a real photo rather than an avatar, or proof of their qualifications.
  • Prioritize a great system for building trust between people. This may be highlighting shared connections, shared groups, or shared interests.
  • Don’t incentivize people with money, incentivize them to build their reputation.


Social web design will become an important part of every interaction designer’s skillset. To do it well, we’ll need to understand some basics about human relationships. If your users’ needs center around strong ties, you’ll design something very different than if they center around temporary ties. Understanding the difference between strong, weak, and temporary ties will help us build better online social experiences.


1, 4 User Interactions in Social Networks and their Implications, Wilson et al. 2009


3 The Economist article quoting stats from Cameron Marlow, sociologist at Facebook

5 Data from a TED talk by researcher Stefana Broadbent

6 PBS article by Henry Jenkins, MIT Professor

7, 8 Nichola Christakis + James Fowler “Connected: The surprising power of our social networks and how they shape our lives” Little, Brown and Company 2009

9 Reports from the Center for the Digital Future, University of Southern California

10 Brave New World of Digital Intimacy

11 I. de Sola Pool, The Social Impact of the Telephone, MIT Press, 1977

12 Quoted from studies by Robin Dunbar

13 Paying People to Yelp

14 Yelping for Dollars

15, 16 Charlene Li + Josh Bernoff, Groundswell, Harvard Business Press, 2008