'Dice' Tests
Participants are asked to attempt to influence the fall of a small physical object, either a die, a coin or similar, with the intention of getting a pre-specified outcome (e.g. a particular number on a die, heads or tails, etc).
Possible problems: Bias due to physical construction of object, bias in throwing technique if participant were allowed to handle object.
Example study: Mitchell, A.M.J. & Fisk, G.W. (1953). The application of differential scoring methods to PK tests, Journal of the Society for Psychical Research, 37, pp. 45-60.
Targets at rest or in motion
Participants are asked to attempt to perturb the target object from it's equilibrium state (e.g. move a compass needle, stop residual oscillations in a torsional pendulum). One of the most famous recent ostensible psychokinetics was the Soviet Woman Nina Kulagina.
Possible problems: Need to disallow possibility of 'normal' influences (hidden magnets, draughts, vibrations, etc).
Example study: Puthoff, H.E. & Targ, R. (1975). Physics, entropy and psychokinesis. In L. Oteri (ed.), Quantum Physics and Parapsychology pp. 129-144, New York: Parapsychology Foundation.
Brought to the public's attention by Uri Geller, such PK tasks ask the participant to attempt to deform the target object (usually some sort of metallic object) without using their physical strength. Participants often have some sort of physical contact with the object, although in controlled experiments this is minimised.
Possible problems: Need to prevent participant from physically bending the object, or substituting a pre-stressed or pretreated object. Possibility of sleight-of-hand techniques being employed.
Example Study; Hasted, J.B. & Robertson, D. (1980). Paranormal action on metal and its surropundings, Journal of the Society for Psychical Research, 50 (784), pp. 379-398.
Also known as 'thoughtography', this phenomenon was made famous by experiments conducted with Ted Serios. The participant attempts to cause an image, or at least some form of anomalous exposure, to appear on an unexposed film emulsion once it is developed.
Possible problems: Need to avoid fraudulent exposures due to chemical contamination or hidden light sources. Care must be taken during developing to avoid accidental light sources. Possibility of electrostatic or ionising radiation effects.
Example study: Watkins, G.K & Watkins, A.M. (1974). Apparent psychokinesis on static objects by a 'gifted' subject: a laboratory investigation, Research in Parapsychologyc 1973, pp. 132-134.