They found that the lower a subject's score on this scale was, the more successful he was at detecting the target.

ECONOMIST: Gory and erotic images can affect your vision

Others researchers use magnetism not only as a way of detecting the target, but also as a way of carrying it to the spin valve.

ECONOMIST: Labs on a chip

In particular, this sensitivity makes the new chips better at searching for strands of DNA. At the moment, such searches require the number of DNA molecules in a sample to be multiplied using a trick called the polymerase chain reaction before there is a decent chance of detecting the target.

ECONOMIST: Labs on a chip

An example of a bottleneck is when people have difficulty detecting a second target if it appears on screen a few tenths of a second after an initial one.

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