Two sensory systems benefit. Widely spaced nostrils sharpen the stereo comparison a shark uses to steer up an odour plume, a mechanism supported by experiments showing hammerheads track scent with strong lateral separation. The ampullae of Lorenzini, jelly-filled pores that detect weak electric fields, are also spread over a larger sweep, letting the shark sweep the seabed like a metal detector.
The cephalofoil brings other benefits. Eyes at the tips give hammerheads unusually wide binocular overlap in front and near-complete visual coverage around the head, and the broad head provides lift that improves manoeuvrability.
The cost side is less discussed. The wide head increases drag, and scalloped hammerheads are exceptionally fragile on capture, with among the highest at-vessel mortality of any shark in longline and gillnet fisheries. That fragility, plus demand for their fins, is why a once abundant schooling shark is now Critically Endangered.