This study uses signal detection measures and secondary task reaction times (STRTs) to examine the effects of structural complexity and information density on processing television messages. Of particular interest are results pertaining to cognitive overload experienced while processing structurally complex and informationally dense messages. When required resources exceed available resources-that is, when a state of cognitive overload is reached-both memory sensitivity and criterion bias drop dramatically while STRTs get faster. The results provide support for the contention that secondary task reaction times are often very fast during highly complex messages because the system is overloaded and therefore resources are shifted from the primary task to the secondary task. Also of interest, the liberal shift in criterion bias starts before overload has occurred, suggesting that criterion bias may be tracking available resources.