Operationally define anxiety using both measurement and manipulation. A testable hypothesis is one that is falsifiable. Gremlin theory which states that gremlins exist but can't ever be observed is an example of a theory which is not falsifiable. Beagles are smarter than poodles. African violets grow better in filtered than in direct sunlight.
Humans are innately aggressive.
You learn more information when studying for an essay test than when studying for a multiple-choice test.