The development of schemes for recognizing additive and alternative effects in a "natural experiment" context.

20 Ss at each of 4 age levels (4th, 6th, and 8th grade and college) were presented a "natural experiment" problem situation in which they were asked to interpret the more complex situations in which (a) either of 2 alternative variables is sufficient to produce an outcome, or (b) 2 variables are additive in their effect on an outcome. Not until adolescence could Ss isolate alternative or additive causes in a multivariable situation, though it is speculated they may comprehend the concept of alternative causes well before this age. Only 65% of college Ss exhibited correct reasoning in one or both situations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)