Children begin to master notions of classes, relations, and quantities. Conservation and seriation are possible, enabling children to formulate hypotheses and explanations about concrete events. Children formulate a hypothesis originating from the concrete data, rather than from internal resources. And, once the hypothesis is formulated, children in concrete operations are reluctant to change the hypothesis, tending instead to alter the data. Adolescents develop the ability to think about mental constructs as objects that can be manipulated, and they can master concepts such as probability and belief.
Cognitive growth appears to stop once substance abuse becomes habitual.
One developmental delay associated with chemical abuse is the ability to think in abstract terms. Thinking then remains at the concrete level. Chemical abuse undermines moral development, which rests on the ability to make ethical choices according to abstract concepts such as justice and social responsibility. Adolescent and young-adult substance abusers think and act more like children with respect to morality and ethics. Adolescent substance abusers cognitively function on a concrete level.