Some people collect teapots, or willow pattern plates, ball point pens, happy meal toys, beer cans - and every now and then they appear in the media with stories about how their collecting has taken over their lives.

Papamoa resident John Tinder had 56,000 ball point pens, with the collection covering every wall in the house and custom shelving.

For non-collectors the questions, ‘why do they do it? And ‘how do they start?' may finally have been answered by the study.

The tipping point theory, as proposed by Professor Gao Leilei, Associate Professor of the Department of Marketing at the Chinese University of Hong Kong (CUHK) Business School and her coauthors, Prof. Huang Yanliu of Drexel University and Prof. Itamar Simonson of Stanford University; say the answer is two. Two items of anything are all it takes to tip someone into collecting mode.

Their theory is that possessing two or more objects of a similar function is perceived as a "neither here nor there" situation, which is difficult to justify.

In order to remedy this awkward situation, people may elicit a goal of building a collection by acquiring more products from the same series. From this point on, having a collection provides the psychological benefits of making the collector believe owing more of the items is reasonable and meaningful.

Their recent study entitled "The Influence of Initial Possession Level on Consumers' Adoption of a Collection Goal: A Tipping Point Effect", they find that people may not always have an initial intention to collect.

However, if they accidentally possess several items which are part of a set, they may spontaneously start a collection on the set of items. Since people need to justify their excessive possessions, they generate the idea that collecting the items would be a good idea. The study further explains that the tipping point for collecting relatively inexpensive items begins with just two items.

Rather than a top-down process where a person simply decides to start collecting stamps one day, the authors explain many collections originate in a more bottom-up process, ad hoc manner. People don't set a prior goal of collecting a set of objects, but commit to the collection later after possessing several similar objects.

While some have an intrinsic preference for the collectible objects, others may purposely decide to build a collection for a particular reason, such as gaining monetary values. For most of us, however, we may neither have a strong liking for something nor a prior commitment in collection at the beginning. So why are we collecting and when do we reach the tipping point when we decide to start building a collection of certain things?

At what point do people start thinking about building a collection? The authors find that the common tipping point happens when people have at least two objects as two is the smallest multiple number that can imply a "waste" and so they have to find a way to justify their possession -- by collecting more.

From seven studies with six of them with participants from Hong Kong and one study with American participants recruited on mturk.com, an online survey platform hosted by Amazon, the authors tested the tipping point effect.

During the 2010 FIFA World Cup soccer game, the authors conducted a study in which they gave participants either one or two boxes of a collectible series of FIFA mints as a gift for taking part in a study. After that, participants were asked to make a choice between another box of FIFA mint and a pen of equivalent value. They found that participants were more likely to choose the FIFA mint box than the pen only when they possessed two boxes of FIFA mint.

The other Hong Kong studies including objects such as refrigerator magnets, Snoopy figurines, 2014 World Cup collectible pins, home decoration pieces, also replicated the tipping point effect that having two or more objects would lead to a higher likelihood for participants to collect for the same series.

In the study with American participants, some participants were assigned a rare and collective Coke can designed in 2007, which was only sold in a limited time in selected cities. The authors found that unlike other studies, when consumers' first-owned collectible is rare and valuable, owning one item is enough to stimulate a desire to collect the series. That is, the tipping point for high-value collectible is one instead of two.

The study has implications for marketers, particularly in China, where collection has a very long history. Chinese people perceive collection as a refined hobby and the Chinese collection market is huge and rapidly growing.

For companies that sell collectable objects or those that use collectable objects in consumer-loyalty programs in China or elsewhere, the research findings offer practical suggestions of how to increase their impact on consumer loyalty.

Instead of highlighting on building a collection right from the start, marketers should instead spark interest among consumers in obtaining individual collectibles. As the study suggests, only after consumers already own a few items should the benefits of building a collection be emphasized.

Offering a single relatively inexpensive item is not enough to generate loyalty. Marketers could instead endow the first few collectibles as free premiums (e.g., give the first two collectible objects for free by making other purchases) or lower the threshold of obtaining the first few collectibles (e.g., lower the requirement of the first few stamps in a loyalty program). Doing so will make it easier for consumers to possess the first few collectable items and commit to collecting the rest of the items and the loyalty program.

The study has implications for other domains of consumer behavior, say the authors. It suggests that a key to motivating customers' repeated engagement in an area of subject, such as forming hobbies and conducting long-term projects, lies in forging the first few trials which help consumers to identify an emerging pattern.

Leilei Gao, Yanliu Huang, and Itamar Simonson (2014) The Influence of Initial Possession Level on Consumers' Adoption of a Collection Goal: A Tipping Point Effect. Journal of Marketing: November 2014, Vol. 78, No. 6, pp. 143-156.