Despite his mother beckoning him to come towards her, this infant hesitates to cross the "visual cliff" – an apparently steep drop that is actually covered by transparent glass. Psychologists in the 1960s found that most infants 6 to 14 months of age were reluctant to crawl over the cliff, suggesting they had the ability to perceive depth. Most psychologists believe that the ability to perceive depth is partly innate and partly a product of early visual experience.

Here's a test you can try to demonstrate how your perception of depth is still live and active. Below are two perfect circles, yet the smaller circle appears distorted. Our brain interprets the converging lines to be adding depth to the screen, as if the solid middle is further aw ...

Angiotensin-converting enzyme (ACE) inhibitors are a remarkable class of drugs for treating hypertension – high blood pressure. These drugs work by interfering with the enzymes that convert an inactive chemical known as angiotensin I to an active form, angiotensin II. Angiotensin II increases the retention of salt and water in the body, raising blood pressure. ACE inhibitors interfere with, or inhibit, the formation of angiotensin II, resulting in relaxed arterial walls and lowered blood pressure.

Since the release of the first ACE inhibitor in the 1980s, known generically as captopril, there are now several different ACE inhibitors available on the market. Many of them are also available in combination with other types of hypertension medic ...