David T. Lykken's saying of "we could avoid two-thirds of all crime simply by putting all able-bodied young men in cryogenic sleep from the age of 12 through 28" demonstrates the understanding that with age.

testosterone level and aggressiveness decrease with age

Explanation:

David T. Lykken's saying of "we could avoid two-thirds of all crime simply by putting all able-bodied young men in cryogenic sleep from the age of 12 through 28" demonstrates the understanding that TESTOSTERONE LEVEL AND AGGRESSIVENESS DECREASE with age.

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.