Examples of "pseudo quantum effects" in history of physics Are there any examples in the history of physics where a phenomenon was considered by the physics community to be not explainable by classical physics and needed a quantum explanation whereas some time later it was noticed that this claim was wrong (perhaps because for instance one "over-idealized" the system, neglected boundary effects or did some other mistakes when "proofing" that there is no classical explanation), i.e. that the phenomenon has indeed a classical explanation? Let me call those effects "pseudo quantum effects" for short. 
Are there such pseudo quantum effects which were today common misconceptions (i.e. where people think that one needs a quantum description but doesn't really do it...)
 A: I think photoelectric effect is a good example. Before formal quantum mechanics(e.g. Schrodinger's equation) was developed, it was believed the effect was due to the quantum nature of light. However, just using Schrodinger's equation+perturbation theory+classical EM wave it is sufficient to demonstrate the existence of photoelectric effect(the electron is still treated quantum mechanically though).
To be brief, perturbation calculation shows that in the presence of a classical EM wave $\vec{E_0}\cos(\vec{k}\cdot\vec{r}-\omega t)$, the transition rate between two energy levels of the atomic system is proportional  to $\delta(E_f-E_i-\hbar\omega)$. So photoelectric effect is really just a resonance effect, and should not be taken as a robust evidence of the existence of photons.
More details about the calculation: The photoelectric effect
A: The "quantum mind" assumption springs to mind. This assumption goes back to Bohm. More recently Penrose has defended a similar position. Yet, nowadays very few physicists would support a brain at 310 K to operate in a quantum coherent way.
