EDITING ESSAYS
578 Part Five • Other Grammar Concerns
typhus, salmonella poisoning, and bubonic plague. (4) Rats have such
huge appetites that it has been estimated that they destroy as much as
one-third of humans’ food supplies every year. (5) It has been estimated
that rats have been responsible for ten million deaths over the past cen-
tury alone. (6) Rats in the laboratory should probably be given credit for
saving as many lives as wild rats have taken.
(7) Rats are used widely in laboratory research. (8) Rats have many
similarities to humans. (9) Young rats are ticklish. (10) When a rat pup
is gently scratched at certain spots, such as the nape of the neck, it will
squeal. (11) The squeal can be heard only with an ultrasound scan.
(12) The squeal has a similar soundgram pattern to that of a human
giggle. (13) Rats can get addicted to the same drugs that humans do.
(14) Rats crave alcohol, nicotine, amphetamine, and cocaine. (15) Rats
can also overindulge. (16) They can continue consuming food or drugs
until they die.
(17) Studies also show that rats, similar to humans, have personali-
ties. (18) They can be sad or cheerful depending on how they were raised
and their circumstances. (19) Rats that have been raised in stable, caring
conditions tend to be optimists. (20) Rats reared in uneven and unreli-
able conditions are likely to be pessimists. (21) Both types of rats can
learn to connect a certain sound with getting food. (22) They also can
associate another sound with no food. (23) However, when they hear a
new sound, the two types of rats react differently. (24) The new sound is
not associated with either food or no food. (25) The optimist will run to
the food dispenser. (26) It is expecting to be fed. (27) The pessimist will
go somewhere else. (28) It is expecting nothing.
ANK_47574_32_ch32_pp563-581 r5 ko.indd 578ANK_47574_32_ch32_pp563-581 r5 ko.indd 578 10/29/08 10:21:26 AM10/29/08 10:21:26 AM