Later studies by Cooper and Shepard (1973, 1975) showed that participants also mentally rotated more recognizable stimuli, such as alphabet letters or drawings of …(ดูไม่ออก). In one study (Cooper & Shepard, 1973), participants were sometimes given a drawing of the letter to be used on a trial, followed by a cue showing the orientation to which the test stimulus would be rotated, before the test stimulus appeared. If these two cues were presented early enough (for example, 1000 milliseconds before the test stimulus appeared), then the participants’ performances were the same for all angles of rotation. Figure 8.4 depicts (ดูไม่ออก) the experimental conditions, and Figure 8.5 shows the results.