In 2011, the New York Times  reported on what inspires and motivates people to share links, videos, images and offers online:
- Define/realize yourself: People share content to give others a better sense of who they are and what interests them (68%). In addition, sharing gives them the opportunity to contribute more strongly (69%).
- Sharing as a form of information management: 73% say that they process information more thoroughly when they share the information. 85 % help others to better understand and process information and events.
- Maintain relationships: People share information online to stay in touch with other people to whom they have no other connection (78%). It also helps them connect with others who share their interests (73%).
- Valuable and entertaining content: 94% consider in advance whether the information will be useful for the recipients. And 49% report that sharing allows them to inform others, influence their opinions or encourage them to act.
- Stand up for a cause: 84% share content because it is an opportunity to support a cause or a topic that interest them.
It is noteworthy that these reasons lie all in a triangle of I, others and content. So, it is not just about showing off.
There is a driving force behind sharing.
As early as 1966, Ernest Dichter [2, 3, 4], who was looking for the factors of successful word-of-mouth propaganda in advertising, outlined four - more or less equally strong - motivations to share content.
Every single one has to do with involvement. Involvement is a term with many conceptualizations . Sometimes the focus is more on the attitudes of the individual, sometimes it is more on the behavioral aspect. Generally, involvement can be defined as the degree of subjectively perceived meaning of behaviour, e. g. in decision-making processes. As involvement increases, the cognitive and emotional engagement of the individual increases. The purchase of a house, for example, triggers more involvement than the purchase of a toothbrush, and - accordingly - the behaviour will be different.
Dichter distinguished four types of involvement in the consumer's relationship to the product:
- Product Involvement describes the urge to report a personal experience (e. g. the user's experience with a product). This kind of engagement can be observed on a company's social media websites when people photograph how they use the product.
- Self-involvement has to do with satisfying emotional needs, such as "getting attention","showing that you belong to it". People share content that expresses their knowledge and opinions. They feel important when they can share the latest news, for example.
- Other-Involvement describes a rather altruistic component. People feel good when they help others. For example, by sharing coupons or product reviews or tagging a friend in a Facebook post.
- Message Involvement refers to the advertising message. Some advertising is so original and entertaining that it itself becomes an object of word-of-mouth propaganda.
These four types can be transferred almost 1:1 to content sharing on the Internet. Thus, product involvement can also be interpreted as content involvement.
Sharing is shaped by motivation.
In an empirical study, Hennig-Thurau et al.  analyzed the motivational structure of users of a Deutsche Bahn opinion platform. They identified eight factors that motivated people to visit the platform:
- strengthening self-esteem,
- seeking advice,
- getting support from the platform,
- gaining social benefits from connecting with others,
- worrying about others,
- talking about negative things with the company,
- receiving economic incentives such as web miles,
- helping the company.
In this context, the authors empirically formed four types of users, which differ by a different combination of the eight factors:
- Self-interested helpers are strongly influenced by their concern for others and by economic incentives.
- Consumers with multiple motives are motivated by all factors except economic incentives.
- Altruists are motivated to help other consumers and businesses.
- Consumer "advocates" are primarily driven by their concern for other consumers.
There are other such typologies or persona approaches that sometimes differentiate even more precisely. It is important to realize that there are different forms of involvement behind these as well. Those who know the motivation of their visitors can address them with tailored content and increase the likelihood that this content will be shared.
Virality of content can be influenced.
To answer the question of why some content performs better, Berger & Milkman  looked at all articles in the New York Times for several months. They found that virality was partly dependent on the emotion that was triggered. Content that provoked an activating emotion (awe, anger or fear) was more viral than content that evoked a rather disabling emotion (e. g. sadness). This result was also valid when controlled for other variables - e. g. the type of content (surprising, interesting, practical - all positively linked to virality) or the type of presentation (prominent, less prominent).
These and other findings led to Berger's six STEPPS  for "contagious" contents:
- Social awareness: We are concerned about what others think about us. And we want to feel "special". That's why we tend to share content that makes us look "good".
- Trigger: This is about staying in touch with your own content and remembering it from time to time.
- Emotions: Feelings are a strong impulse for sharing, especially when they have an activating effect.
- Publicity: People are looking for information. In order to be found, the content should be clearly visible.
- Practical value: Useful information is often shared. Therefore, the practical value of the content should be emphasized.
- Stories: Stories are particularly suitable to be passed on because we are used to thinking in stories.
- Virality is not necessarily an inherent feature of content.
- Rather, it depends on the value that users recognize in the content for themselves and others.
- This value is more obvious for some content and less obvious for others.
- It is worthwhile for content providers to highlight this value (e. g. with the six STEPPS).
 The New York Times Insights (2011): The Psychology of Sharing. Link
 Dichter, Ernest (1966), "How Word-of-Mouth Advertising Works," Harvard Business Review, 44 (6), 147-66.
 o. V. (2011). Sex and advertising - Retail and therapy Link
 Moore, J. (?). Ernest Dichter on Word of Mouth Marketing - Ernest Dichter is a name every marketer should know. Link
 Robert N. Stone (1984),"The Marketing Characteristics of Involvement", in NA - Advances in Consumer Research Volume 11, eds. Thomas C. Kinnear, Provo, UT: Association for Consumer Research, Pages: 210-215.
 Hennig-Thurau, T., Gwinner, K. P., Walsh, G., & Gremler, D. D. (2004). Electronic word-of-mouth via consumer-opinion platforms: what motivates consumers to articulate themselves on the internet?. Journal of interactive marketing, 18(1), 38-52. Link
 Berger, J., & Milkman, K. L. (2012). What makes online content viral? Journal of marketing research, 49(2), 192-205.
 Berger, J. (2016). Contagious: Why things catch on. Simon & Schuster.