The person next to me had plenty of heavy duty tape and when he started struggling to tape his pieces of cardboard to the wall I offered a helping hand. He then left however he had 'abandoned' his tape. So a bit immorally, I borrowed some of his tape. When he returned he assured me it was no problem that I had used some, I thanked him hugely and he then let me borrow some more.
By helping him previously he was more likely to then help me later one due to this social norm of reciprocity which we implicitly abide to. Support for this effect has been found by Bartlett and DeSteno (2006) who found another factor may also influence this effect. The participants were in one of 3 conditions. The first was the gratitude condition where the computer, in which they were completing a menial search task on, broke. A confederate, who was believed to be another participant, came to try and help fix the problem. The second condition induced amusement in the participant through showing them a TV clip. A neutral condition was also used where they only met the confederate briefly. Helping behaviour was measured in the act of doing, and time taken to do, a very boring survey for the confederate.
They found that the greatest helping behaviour was seen in the gratitude condition due to the reciprocity element seen in this specific scenario where by helping with the broken computer, the participants were more likely to help the confederate back later (shown through greater time spent on the survey).
This figure shows how as well as reciprocity playing a key role in this increase in helping behaviour in the participants of the gratitude condition, the gratitude shown may have also played a role. In my experience with the tape I thanked the individual for him letting me use his tape (or not hating me for using it) and this may have increased the chance of him allowing me to use more, which he did.
So overall, as well as providing a helping hand in the beginning, and being very grateful for his supply of tape at my time of need, I may have increased the chances that he would let me use more which I definitely needed. Life lesson: help other as much as possible, be as grateful as possible, and at your time of need they'll be there with the heavy duty tape in hand.
Bartlett, M. Y., & DeSteno, D. (2006). Gratitude and prosocial behavior helping when it costs you. Psychological science, 17, 319-325.