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The book "Productive Thinking", by Gestalt psychologist Max Wertheimer, was published over 50 years ago, yet it continues to wield influence. The book's argument on productive thinking, and why it is still relevant today, are the focus of this paper. Productive thinking involves going from a situation of bewilderment or confusion about some issue to a new state in which everything about the issue is clear. The process involves a kind of reorganization, and marks a transition from a state that is meaningless to one that is meaningful. Aural and visual examples of productive thinking are presented, along with word games and the importance of problem reformulation. A number of logic problems are presented and the possibility of their solution is explored. Many scholarly reactions to the book's theme are presented in detail, and some of the research that has been initiated by productive thinking is explained. The ascendance of computer-based, information processing as a paradigm for cognitive psychology is discussed, as well as its application to productive thinking. Contains 50 references. (RJM)

Classical molecular-dynamics simulations have been carried out to investigate densification mechanisms in silicon dioxide thin films deposited on an amorphous silica surface, according to a simplified ion-beam assisted deposition (IBAD) scenario. We compare the structures resulting from the deposition of near-thermal (1 eV) SiO$_{2}$ particles to those obtained with increasing fraction of 30 eV SiO$_{2}$ particles. Our results show that there is an energy interval - between 12 and 15 eV per condensing SiO$_2$ unit on average - for which the growth leads to a dense, low-stress amorphous structure, in satisfactory agreement with the results of low-energy ion-beam experiments. We also find that the crossover between low- and high-density films is associated with a tensile to compressive stress transition, and a simultaneous healing of structural defects of the {\em a-}SiO$_2$ network, namely three- and four-fold rings. It is observed, finally, that densification proceeds through significant changes at intermediate length scales (4--10 \AA), leaving essentially unchanged the ``building blocks'' of the network, viz. the Si(O$_{1/2}$)$_{4}$ tetrahedra. This latter result is in qualitative agreement with the mechanism proposed to explain the irreversible densification of amorphous silica recovered from high pressures ($\sim$ 15--20 GPa)., Comment: 12 pages including 10 postscript figures; submitted to Phys. Rev. B; related publications can be found on web site http://www.centrcn.umontreal.ca/~lewis