This is what i have been using trying with face/ eye detect on and off.
Tracking:This setting is available only when the focus mode is set to [Continuous AF]. When the shutter button is pressed and held halfway down, the product tracks the subject within the selected autofocus area. Point the cursor at [Tracking] on the [
Focus Area] setting screen, and then select the desired area to start tracking using the left/right sides of the control wheel. You can also move the tracking start area to the desired point by designating the area as a [Tracking: Zone], [Tracking: Spot S]/[Tracking: Spot M]/[Tracking: Spot L] or [Tracking: Expand Spot].