[sparrowInHand]

Particles in heat are more active, as in brownian motion puts them allover the place, the cooler things get, the smaller the ripples, the less likely to interact with another particle, by transfering that ripple.

Now in solid materials, that neighbour is always there to distribute any energy to everyone equally. But from solid to gas, there is only the surface and a gases density is lower, so the transfer propability shrinks again.

[taylorius]

But that's hot vs cold. As I understood it, this article is talking about difference in rate of heating vs. cooling, from the same starting temperature.