Kosslyn's experimental results may be invalid as:
- Subjects' tacit knowledge of real objects makes them think that they are supposed to work with images in the same way that they work with real objects. As a result, subjects are not literally scanning or rotating images, but are mentally simulating a real scanning or rotation of a real object. That is, the task demands of the experiment confound its results.
- The experimenter is able to affect the subject with "non-verbal cues, tacit messages... loaded answers to questions and so on" (p.544). This gives rise to a variety of undesirable experimenter affects.
Charles L. Richman, David B. Mitchell, and J. Steven Reznick (1979)—as articulated by Zenon Pylyshyn (1981).