In this research, we applied the operating characteristic of the receiver (ROC) to evaluate item-recognition memory by means of open class words (CA) and closed class words (CC). The purpose was to evaluate memory processes and models, according to the type of stimuli used: words in Spanish, classified according to grammar characteristics. To register the data, a rating scale was applied to obtain the appropriate response levels. Statistically significant differences between the processing of both types of words were obtained. We evaluated models of threshold, continuous, and unequal variance. As a result, we could contribute to the resolution of the present controversy about the models adapted to evaluate the memory of item recognition. Lastly, the differentiation and integration of the models from an empirical point of view is discussed.