<p>Four experiments assessed the effect of practice with similar stimuli on the ability of adult humans to identify a target stimulus by means of same/different judgments. The study found the target identification task sensitive to the effect of practice and to stimulus length and distinctiveness (Experiments 1 and 2). By the other hand, training improved performance on same but not in different trials (Experiment 3 and 4), being these findings apparently not related to any potential response bias. The target identification task was then sensitive to variables related to perceptual learning, providing some new insights about the potential biases to respond same or different. Further, it raised the hypothesis that the stimulus recognition and differentiation process might appear dissociated in such kind of task.</p>