Topic drift

Topic drift is the naturally occurring phenomena where-by related but off-topic subjects are introduced into topic debates. For example, chess to strategy to real-time strategy games (the latter of which may be irrelevant to chess as a turn-based strategy game).

Psychology
Akin to wiki-walk, individuals bring up related topics to a subject based on relative interconnectivity to the subject, which may in turn result in relative subjects related to the new subject being brought up.

This is a natural progression as the human mind often becomes bored with a singular, unchanging topic, and people are often eager to discuss related ideas that they know more about as an opportunity to further discuss their own ideas and topics with their peers as part of acceptance psychology.

Learning follows a similar pattern in that individuals may investigate similarly related chains of information even if it takes them further and further away from the original subject matter. Information is theoretically also appended in a similar manner akin to tree-like lists of information or as sub-referencing nodes that relate to one another.

Counteraction
Naturally occurring topic drift shouldn't be intrinsically discouraged as it may produce positive results in that individuals explore related subjects and thus come up with solutions or ideas that may relate to the subject matter. Malicious topic drift however classifies as derailment and should be counteracted with re-rail attempts. Individuals should be gently reminded to keep to a similar topic if natural but non-malicious topic drift occurs.

Gentle reminders may however result in reverse Milgram experiment results, however aggressive or commanding behaviour may also trigger instinctive oppositional behaviours causing individuals' behaviour to worsen.