Which feature do all the studies highlighting the possible importance of early experience in animals have in common

A)  The researchers used very small samples. 
B)  They used species that cannot be logically compared to humans. 
C)  They used relatively crude measures of brain growth. 
D)  They used extreme conditions to make their comparisons.

All the studies highlighting the possible importance of early experience in animals have in common the use of extreme conditions to make their comparisons. These extreme conditions could include sensory deprivation, social isolation, or manipulations of early experience in a way that is not reflective of typical developmental circumstances. This approach allows researchers to identify the potential impact of early experiences on brain development and behavior in a more controlled manner.