In a dichotic listening task, different stimuli are delivered to each ear. The subject is told to attend to one signal over the other. Which of the following is most likely to be noticed in the unattended ear?

A) a shift in the speaker's language
B) a change in the speaker's gender
C) discussion of a controversial topic
D) all of the above are equally likely or unlikely to be noticed

In a dichotic listening task, the subject's attention is directed to one ear, while stimuli are presented simultaneously to both ears. When the attention is focused on one ear, it is less likely that the subject will notice stimuli presented in the other ear. However, any feature that is sufficiently salient or important may still capture the attention of the subject, even if it is presented in the unattended ear. Therefore, any of the options listed in the question may or may not be noticed, depending on various factors such as the subject's cognitive load, motivation, and arousal level. As such, all of the above options are equally likely or unlikely to be noticed in the unattended ear.