Final answer:
The locations on the scalp that might be sensitive during a scalp massage include the crown, hairline, behind the earlobes, and sides of the head, due to the presence of nerve endings and variable tissue thickness.
Step-by-step explanation:
During a scalp massage, certain locations might be more sensitive than others due to the presence of nerve endings and the thinness of the scalp tissue in these areas. The locations mentioned - at the crown, along the hairline, behind the earlobes, and at the sides of the head - all have differing levels of sensitivity. The hairline is especially sensitive because it is where the facial nerves extend to, while behind the earlobes contain a thinner layer of skin and are closer to the occipital nerves. The crown might also be sensitive because it is a pivotal point where several nerves meet, and the sides of the head may be sensitive due to the temporal muscles underneath the skin.