Cross sectional research design are usually used to understand the dominant character or features in a population at a particular point in time. Some of the characteristics of a this study design are; takes place at one time, allows researchers to compare certain characteristics such as age, can provide information about what is happening with a certain population and what is happening in another population say 5 years later, and then use this information as a basis of comparison. Researchers do not use this study to show cause-and-effect, but it is used mainly for correlational analysis.
Intelligence is a set that forms all the intellectual characteristics of an individual, that is, the faculty of knowing, understanding, reasoning, thinking and interpreting. Intelligence is one of the main distinctions between humans and other animals.