Necker Island (British Virgin Islands) would survive their castaway adventure for at least three weeks, but as McCullin later recounted, "because of our gathering weakness ... out of temper, and out of water, we hoisted the red flag and were taken off in the early hours of the fifteenth day". According to McCullin, there was nothing idyllic about the desert island: "The mosquitos and other insects were more venomous and persistent than any I had encountered in Vietnam or the Congo." Richard Branson's "Extreme Tech Challenge" has been hosted annually at Necker Island since 2015. Described as one of the largest technology competitions in the
Necker cube occurs to the second interpretation. Similarly, if one is viewing the second interpretation, focusing on the left side of the cube may cause a switch to the first. The Necker cube has shed light on the human visual system. The phenomenon has served as evidence of the human brain being a neural network with two distinct equally possible interchangeable stable states. Sidney Bradford, blind from the age of ten months but regaining his sight following an operation at age 52, did not perceive the ambiguity that normal-sighted observers do, but rather perceived only a flat image. During the 1970s, undergraduates