The effects of types of both memorized items and probes (digit, word, and dot pattern), using Sternberg's character-recognition procedure, were studied. Reaction time (RT) was a linear function of the set size of memorized items consistent with a serial search model. Response type (positive or negative) affected the encoding time (intercept of RT function) or probes only, and was explained by a rechecking operation. Finally, probe types had effects on both search rate (slope) and encoding time, but types of memorized items affected neither. These results were discussed in terms of the encoded information and its relations to search operation. (Author)