The pilot flying the ill-fated Atlas Air B-767 was probably suffering from Somatogravic Illusion caused due to acceleration of the aircraft. The apparent pitch up experienced could have been as high as 80 degrees nose up. The pilot therefore pitched the nose down fearing an imminent stall.
The Captain, at a later state may have been pulling back on the control column as the co-pilot pushed forward. This caused a spilt elevator where left half moved up and right half moved down.
The net effect was that the aircraft continued to descend at a high rate.
The GPWS which activates warnings to alert the pilots of dangerous terrain did not activate. Could the activation of the warning pull out the copilot from the illusion?