Trick questions or toying with emotions or our subconscious desires.
There are a number of ways that games can use text, graphics or sounds to subconsciously influence our decisions.
1) Toying with Emotions - Games may make players feel bad for making a choice or rejecting an offer. For example, maybe the point of the game is to save cute little bunnies from the evil foxes. When you lose a level, the game may show you a picture of a sad little bunny and say something like "Spend 2 coins and save this little bunny." Even though you know it's not a really bunny, it is still toying with your emotions and trying to get you to spend money on the game. Another example could be to make you feel bad for not helping your team. Because of social pressure, the game can emphasize that you are letting your team down to get you to play more.
2) Trick Questions - Sometimes games try to trick you into doing something. Maybe they give you an option to spend coins on something, but they make the "Yes" button red instead of green. We are habituated to press a red button to cancel something, so mixing the colors up can confuse us into pushing the wrong button. Other ways of tricking us is to make one button bigger than the other. People are more likely to click the bigger button. Using checkboxes to opt-out of something is also a way trick people, since checkboxes are usually used to opt-in.
3) Subconscious Associations - People like cute things or tasty things. This is why a lot of games use cute animals or candy imagery. In-game candy attracts the subconscious desire for sweets and makes the game more desirable.
4) Over-the-top Feedback - This is most exemplified by a casino floor. The constant ringing and dinging and over the top sounds of people winning huge jackpots toys with our emotions. Games do this by using extreme graphics, sounds and vibration when you win or lose.