Jeremy Cherfas

Signals for food: reinforcers or informants?

Ring doves pecked one of two keys for food. Pecks at the chosen key then stopped being reinforced, and the signals that normally preceded food were either present or absent. In the presence of signals for food, the dove switched to the second key more quickly. When only one key was used, the same signals acted, as expected, to keep the bird pecking the extinguished key.

East Germany Struggles to Clean Its Air and Water In the midst of dramatic political changes, environmental planners in East Berlin draw up a scheme to restore what's left of nature

East Germans are working hard on a strategy to improve their polluted environment. Industrial plants are largely responsible for this pollution. A shroud of haze veils the suburbs of East Berlin. Far to the south the giant power plants around Leipzig pour more dust and sulfur dioxide into the air than in any other country in Europe. More than 90% of the countrys electricity comes from brown coal, accompanied by prodigious quantities of dust and sulfur dioxide: almost 6 million tones of sulfur dioxide and more than 2 million tones of dust in 1988. East Germany enjoys some of the cheapest energy in the world, and the worlds third highest energy consumption per capita, behind the United States, and Canada. Naturally, is also suffers air quality and health problems. The country is trying to cut down on consumption and clean up on generation. Actually, water quality is the number one priority, which unlike air is in very short supply.