People who are obese  have a worse memory than their thinner friends, a small study shows.  Tests on 50 people showed that being overweight was linked to worse "episodic memory" or the ability to remember past experiences. The study in the Quarterly Journal of Experimental Psychology argues that a less vivid memory of recent meals may lead to overeating. However, other aspects of memory -- such as general knowledge -- show no signs. Tests on rats have previously shown that with burgeoning waistlines come poorer performances in memory tests, but the evidence in humans has been mixed. Fifty people with a Body Mass Index (BMI) ranging from 18 (healthy) to 51 (very obese) took part in a memory test -- a bit like doing a treasure hunt on your own. They had to "hide" objects at different times and on different scenes displayed on a computer screen. They were later asked to recall what they had hidden, when and where. The results showed obese people's scores were 15% lower than thinner people. Dr. Lucy Cheke, from the University of Cambridge, told the BBC News website, "The suggestion we're making is that a higher BMI is having some reduction on the vividness of memory, but they're not drawing blanks and having amnesia  . As a matter of fact, if they have a less strong memory of a recent meal, with a less strong impact in the mind, then they may have less ability to regulate how much they eat later on." Hunger hormones  play a huge role in how much we eat, but it has already been recognized that our minds have a key role too.  Dr. Cheke concluded, "It is too early to talk in terms of advice, but we are certainly beginning to observe how obesity causes itself to continue." Which of the following is TRUE about the experiment?
The researchers compare the performances of people with various BMIs. Fifty subjects are required to seek for objects hidden by the researchers. All aspects of memory will be influenced by obesity. The number of rats tested is the same as that of people.