In the philosophy of science, observations are said to be “theory‐laden” when they are affected by the theoretical presuppositions held by the investigator. The thesis of theory‐ladenness is most strongly associated with the late 1950s and early 1960s work of Norwood Russell Hanson, Thomas Kuhn, and Paul Feyerabend, and was probably first put forth (at least implicitly) by Pierre Duhem about 50 years earlier 
Two forms of theory‐ladenness should be kept separate: (a) The semantic form: the meaning of observational terms is partially determined by theoretical presuppositions; (b) The perceptual form: the theories held by the investigator, at a very basic cognitive level, impinge on the perceptions of the investigator. The former may be referred to as semantic and the latter as perceptual theory‐ladenness.
- Schindler, Samuel (2013): 'Theory-ladenness', In: Kaldis, Byron (ed.) Encyclopedia for Philosophy and the Social Sciences. Sage
- Samuel Schindler (2013). Theory-laden experimentation. Studies in History and Philosophy of Science Part A, Volume 44, Issue 1, p. 89.
- Schindler, Samuel (2013): 'Theory-ladenness', In: Kaldis, Byron (ed.) Encyclopedia for Philosophy and the Social Sciences. Sage ISBN 9781412986892 (penultimate draft):