Conspiracy theorists hang onto theories despite the indicators you would expect to see if it were true not being there.
The argument
People often believe in conspiracy theories because they hold on to degenerating research programs. If something is true, there are certain outcomes we can reasonably see along the way. Conspiracy theorists, when these outcomes do not appear, do not let go of the theories, holding on to the degenerating research programs instead of re-evaluating. For instance, the sheer amount of people that would be needed to keep a conspiracy theory secret over time is such that for many things, they could reasonably be expected to be revealed. However, theorists ignore this, instead continuing to cling to the degenerating research program.
Premises
Counter-arguments
The Lakatosian language of "degenerating research programmes" describes how conspiracy believers reason but does not fully explain why they adopt or retain the belief in the first place. The sibling positions note that clinging to a failing theory despite disconfirmation is characteristic of motivated reasoning driven by distrust, social identity or psychological need — so the "cognitive error" account may be redescribing a symptom rather than identifying the cause. Moreover, not every unfulfilled prediction marks a degenerating programme: some conspiracies are genuinely hard to disconfirm because absence of evidence is exactly what a believer would expect, so labelling all such persistence a bare cognitive error risks begging the question against them.
Rejecting the premises
[Rejecting P2] That believers "cling" to a failing programme may reflect motivated reasoning rooted in distrust or identity rather than a purely cognitive error, so the cognitive-reaction framing may mistake a mechanism for a cause. [Rejecting P3] The "many people would reveal it" heuristic is itself contestable — believers argue secrets are kept by compartmentalisation — so treating their refusal to update as simple error assumes the conclusion. [Rejecting C] Even if the reasoning pattern is real, it describes how the belief persists, not why it is held; the other positions' social and psychological accounts may do the explanatory work the cognitive story only redescribes.