Conceptual ambiguity and empirical confusion regarding the nature and measurement of anxiety have resulted from the failure to distinguish between anxiety as an emotional state and individual differences in anxiety as a personality trait. The distinction between states and traits is an old one. In the first century BC, for example, Cicero (106-43 BC) distinguished between anxiety and anger as emotional states, and anxiousness and irascibility as

personality traits. Spielberger (1966) suggested that emotional states and personality traits were analogous to the concepts of kinetic and potential energy in physics. Like kinetic energy, psychological states describe the expression of energy here and now. Personality traits are like potential energy in that they refer to latent dispositions to respond with certain types of reactions under appropriate circumstances.