Special types of Kamma Vipaka

According to Buddhism the same good or bad deed has different results depending on who you are and the person being affected by your action, a few examples: Giving food to a Buddha x Giving food to an ordinary person. Lying and cheating if you are a monk x if you are a lay person. Killing your parents x Killing ordinary people. Ok, it does make sense, but the question is: Is there a simple logic behind it? Depending on the impact in the world per haps?! And what kind of force understands that you are doing the good/bad deed against a different (not ordinary) being?