Hi soup006,
It depends on the specific chemical formulation of the memory foam (or gel memory foam). There is a very wide range of different memory foam formulations with different properties including density, response time, temperature sensitivity, breathability, and firmness. Many of the newer memory foam formulations or gel memory foam formulations are more breathable and have a faster response time than older formulations because of consumer complaints about heat and about the “stuck in sand” feel that can go with some memory foam formulations that have a slower response time. There is more about the different properties that can be formulated into of different types of memory foam (gel or non gel) in post #9 here and in post #8 here.
Phoenix