You're a terrible sister! Now do what I want.

I received the above messages from my sister yesterday after I missed a phone call from her. Having been reminded of what a terrible sister I am, I rang her back immediately and we spoke for half an hour while I ignored the friend I was with, who sat quietly in the background playing candy crush.

My sister knows how to play me well.

In this instance, she has successfully used a guilt trip to persuade me to do what she wants. This guilt trip has three key parts.
1) She let's me know she's unhappy, and I don't want her to be unhappy so I start wondering if there's anything I can do to make her not unhappy.
2) She suggests her unhappiness is exacerbated by my not loving her (which I do in spite of her shameless emotional manipulation), so making me feel partly responsible for her unhappiness.
3) She implies that my lack of love is proved by me not answering her phone call, making it obvious that I have to call her to show I do love her and make her stop being unhappy.
The over dramatic 'WWHHHHHAAAAAAAAAYYY' is a nice touch too, you can really feel her pain.
She made me feel guilty for not answering the phone and so to assuage my guilt I called her, thus giving in to what she wanted.

The power of guilt to get people to do things you want them to do but they don't necessarily want to do has been demonstrated by Carlsmith and Gross (1969). In this study, participants were told they would be delivering painful electric shocks to another participant (actually a confederate), or that they would be providing feedback in a non-painful way. After this procedure, a confederate asked the participant to make some phone calls regarding a petition to save redwood trees in North America. The study found that participants were more likely to agree to make the phone calls if they had been in the electric shock (guilt inducing) condition. Compliance was highest when the request was made by a confederate who had witness the participant giving the shocks, but was not actually the 'recipient' of the shocks, suggesting the raised compliance was no due to sympathy but rather to guilt.

The table above is taken from Carlsmith and Gross' (1969) original paper and shows all the conditions they ran, with the first column labelling the emotion they used to explain why people complied to the request. The bottom row, representing general guilt, has the highest level of compliance. And so, just like the poor subjects of Carlsmith and Gross' (1969) experiment, I was made to feel guilty for my actions and so persuaded to do what was asked of me. It makes me feel a little better to know I'm not just a pushover - the guilt gets to all of us.

Carlsmit, J. M., & Gross, A. E. (1969). some effects of guilt on compliance. Journal of Personality and Social Psychology, 11, 232-239.