Psychokinesis refers to the direct influence of the mind on a physical system that cannot be explained by known physical forces. Examples include moving or distorting objects and influencing random number generators. The study of purported psychokinetic phenomena is part of parapsychology, although research has shifted focus from large-scale effects to attempts to influence dice and random number generators. Parapsychologists distinguish between macro-PK (large effects visible to the naked eye) and micro-PK (minor effects only visible through statistical analysis). Current research investigates both types of PK, particularly microscopic effects studied using random event generators. However, anomalous perturbation experiments and research into psychokinesis are generally not considered mainstream science due to lack of reliable proof.