the answer is balance tabs. The balance panels assist during manual reversion. I was going to explain it, but I forgot, I have an official explanation available. All B737s have balance tabs (along w/balance panels) on the Ailerons and Elevator to assist during Manual reversion. Here it goes:
AILERON AND AILERON TRIM CONTROL SYSTEM - BALANCE PANEL AND TAB
Purpose
The aileron balance panels and tab decrease the force necessary to move the aileron in flight.
Location
The balance panels are in the number one through four aileron bays.
Physical Description
The forward edge of the balance panel attaches to the wing structure through an idler hinge. The aft edge attaches to the aileron.
Seals connect the hinge assemblies along the two sides of the balance panel. This makes two separate chambers. The upper chamber vents to the airstream over the wing and the lower to the airstream under the wing.
Functional Description
When there is no lateral input, pressure forces occur across the balance panel and keep the aileron in the neutral position. When the aileron moves, it causes a differential pressure. This moves the balance panel in the opposite direction of the aileron movement.
As the balance tab moves, differential forces occur at the tail of the aileron. They help the power source that moves the aileron. These forces are always applied but they are most useful during manual control.