Final Answer:
Even if age is positively correlated with the speed of processing, it would be incorrect to conclude that age directly "caused" this increase. Correlation does not imply causation, and establishing causation requires experimental studies.
Step-by-step explanation:
Correlation indicates a statistical relationship between two variables, such as age and speed of processing. A positive correlation suggests that as one variable increases, the other tends to increase as well. However, correlation alone cannot establish a cause-and-effect relationship. In this case, while age and speed of processing may be correlated, it doesn't mean that age is the cause of changes in processing speed.
To establish causation, experimental studies are necessary. These studies involve manipulating one variable (independent variable) to observe its effect on another variable (dependent variable) while controlling for other factors. Only through experimental research can causation be confidently determined.
Therefore, the answer is that option C: "Even if age is positively correlated with speed of processing, we cannot conclude that age 'caused' this increase because only experimental studies can demonstrate cause and effect relationships."