Bass Left Hand Position
Bassists have a special left hand position that differs slightly from the cello in that the first finger must extend backwards slightly to provide correct finger spacing. Bassists do not use their third or fourth finger alone until they reach higher positions because the distance between the pitches is too large. Instead, third and fourth finger work together.
If you place your left
hand in position and
then bend your third finger into your palm (lower image at left), you
can clearly see that the space
between 1 and 2 is smaller than the distance between 2 and
4, unless you adjust your first finger.