The mediation of external variables in the technology acceptance model

TAM specifies a pathway of technology acceptance, from external variables to beliefs, attitudes, and system usage. We tested one of its assumptions that the ‘perceived ease-of-use’ and ‘perceived usefulness’ constructs fully mediate the influence of external variables on usage behaviors. Using a survey of 125 employees of a U.S. Government agency we found, contrary to the normally accepted assumption, that external variables could have direct effects on usage behavior over and above their indirect effects. We also found that TAM is significantly and consistently better at predicting frequency than volume of usage.