Example headsets and methods for gathering electroencephalographic signals are disclosed herein. An example headset disclosed herein includes a cap to be worn on a head of a person and a first electrode carried by the cap. The first electrode holder defines a first opening therethrough. The example headset includes a first electrode that insertable into the first opening. The first electrode has a first length and is adjustable in the first opening to a first plurality of discrete positions having different depths of insertion relative to the first opening. The first electrode is to engage the head of the person when inserted a sufficient depth into the first opening. The example headset also includes a second electrode that is interchangeable with the first electrode and insertable into the first opening. The second electrode has a second length, greater than the first length, and is adjustable in the first opening to a second plurality of discrete positions having different depths of insertion relative to the first opening. The second electrode is to engage the head of the person when inserted a sufficient depth into the first opening.