Reading: Multiple Choice: Question 1

A woodpecker striking a tree trunk decelerates its head at forces that would concuss almost any other vertebrate almost instantly, repeated dozens of times a second during a single bout of drumming. Yet under normal conditions in the wild, woodpeckers show no obvious sign of brain injury from this behaviour, a puzzle that has drawn the attention of biomechanics researchers for decades. Early explanations focused almost entirely on the skull's internal structure, assuming that some part of the head must be acting as a built-in cushion to soak up the shock before it reaches the brain.

Dissections identified several candidate features. Plates of spongy, air-filled bone sit at the front and back of the skull, and the hyoid bone, a long, flexible structure that in most birds simply supports the tongue, wraps almost the entire way around a woodpecker's skull, an arrangement researchers have compared to a seatbelt holding the head and beak assembly firmly together. The upper and lower parts of the beak also differ slightly in stiffness, a mismatch some biomechanists argued directs stress away from the brain case and toward the beak's tip instead, where the bird can better tolerate it.

This shock-absorber picture, in which the spongy bone plates were assumed to act as a built-in cushion, was widely accepted until a 2022 study combining high-speed video with computer modelling of skull movement during impact reached a strikingly different conclusion, calling that cushioning hypothesis into question. The researchers found barely any relative motion between the skull and the brain during a strike, suggesting the skull is not compressing to absorb an impact so much as remaining rigid enough that very little of the force ever reaches brain tissue in the first place. Under this newer view, a woodpecker's brain survives less because of internal padding and more because its small mass, combined with the extremely short duration of each strike, keeps the resulting strain below the threshold for injury.

Even so, the underlying anatomy has already proved useful outside biology. Engineers studying the layered stiffness gradient running through a woodpecker's beak and skull have borrowed the principle for designing impact-absorbing structures, including cycling and industrial helmets and the protective casings built around aircraft flight recorders, both of which must survive a single violent impact without transmitting damaging force to whatever they are protecting.

Choose the correct letter, A, B, C or D.

1. According to the passage, what has long puzzled researchers about woodpeckers? A. They peck at a noticeably slower rate than most other woodland birds. B. They avoid pecking on the hardest tree trunks to reduce the risk of injury. C. Their brains appear undamaged despite impact forces that would concuss other animals. D. Only a small number of woodpecker species peck on solid wood.

2. According to the passage, what does the hyoid bone do? A. It wraps around the skull in a way researchers have compared to a seatbelt. B. It cushions the brain with extra fluid stored in the skull. C. It is present only in a handful of woodpecker species. D. It absorbs sound rather than mechanical force.

3. What did the 2022 study using high-speed video and computer modelling suggest? A. The skull functions mainly as a shock absorber that cushions the brain. B. Woodpeckers deliberately slow their pecking speed to limit the force involved. C. Fluid inside the skull plays the dominant role in protecting the brain. D. The skull may be rigid enough that very little of the impact reaches the brain at all.

4. According to the passage, the idea that spongy bone acts as a cushion A. has been fully confirmed by the 2022 study. B. has been challenged by more recent biomechanical modelling. C. was first proposed by aerospace engineers studying flight recorders. D. applies only to the beak rather than to the skull itself.

5. According to the passage, insights into woodpecker skull structure have been applied to A. improving the aerodynamics of aircraft wings. B. developing lighter beaks for agricultural robots. C. designing impact-absorbing structures such as helmets and flight-recorder casings. D. creating adhesives used in furniture manufacturing.