Impressionable years hypothesis refers to proposition that adolescents and young adults are more easily persuaded than their elders.

The impressionable years hypothesis, also known as the sensitive period hypothesis, suggests that there are certain critical periods during childhood and adolescence where environmental experiences have a greater impact on development than during other periods of life. These critical periods are thought to be a time when certain cognitive, social, and emotional skills are particularly malleable and susceptible to change.

The idea behind the hypothesis is that early experiences can shape the way the brain develops, leading to long-lasting effects on behavior, cognition, and emotion. For example, research suggests that early exposure to stress or trauma can increase the risk for mental health problems later in life, while positive experiences during childhood can promote resilience and enhance well-being.

Some specific examples of critical periods identified by the impressionable years hypothesis include language development in early childhood, social development during adolescence, and the development of emotional regulation skills throughout childhood and adolescence.

However, it's important to note that the impressionable years hypothesis is not without controversy. Some researchers argue that development is much more complex and dynamic than a simple critical period model can account for, and that the impact of early experiences may be more dependent on an individual's genetic makeup, environmental context, and ongoing experiences throughout life.