Exemplar of a Lab Report
Differentiation between salt and sugar
An analysis of the effect that removing the amount of saliva on the tongue has on the
ability to differentiate between salt and sugar
Sample Studetnt
IB Biology 2 HL
Instructor: Gena Barnhardt
February 12, 2008
Differentiation between salt and sugar
Abstract:
In this lab the relationship between one’s ability to taste and one’s saliva was
tested. The subjects dried the saliva off of their tongues and were asked to determine the
difference between salt and sugar. This lab showed that there was a significant difference
between the subjects’ abilities to perceive the taste with and without drying the tongue.
The data supports the hypothesis that a lack of saliva makes it harder to determine the
difference between dry tastes.
ntroduction
Humans have taste receptors in the taste buds of the tongue. On each taste bud
there is between 1 and 200 cells and there are over 10 000 taste buds on a single tongue.
There are five basic tastes that the tongue perceives: salty, sweet, bitter, sour and umami
(Ritter et al. 1993). Different areas of the tongue have heightened perception of one of
the five main tastes. Though different areas have a heightened perception of one of the
five tastes, all areas of the tongue have receptors for each of the different tastes.
Taste is also closely related to smell. When we eat food our brain receives
messages from all of the different chemoreceptors in the mouth as well as
chemoreceptors in the nose which detect chemicals in the smell and taste of the food
(Ritter et al. 1993). Though the nose is responsible for allowing humans to detect more
complex tastes, the five basic tastes are primarily detected on the tongue. Therefore, in a
test to determine the effect saliva has on the tongue’s ability to taste it would be best to
use two of the five basic flavours. Two of the flavours are salty and sweet and both salt
and sugar look and feel similar so it would be easy to use them in a test between the two.
Also, they are conveniently in solid form which is needed to test the effect of saliva
because liquid taste substances would already be dissolved and would still be detected in
the absence of saliva on the tongue.
The tongue not only plays a significant role in tasting food, it also helps to
mechanically break down the food we eat which starts the process of digestion.
Saliva is excreted into the mouth from salivary glands. Saliva is present in the
mouth to protect humans from some bacteria and viruses. But saliva’s main role in the
mouth is to start the break down of food because it contains enzymes (specifically
Differentiation between salt and sugar
amylase) which break down food and dissolves solid foods so that they can easily access
the taste pores and bind to taste receptors (Gavin 2006). Saliva also affects the taste of
some foods; it decreases the intensity of sour tastes and alters the sweet and salty taste
(ncbi **not ptoper)
Taste is perceived when chemicals enter the taste pore and are detected by taste
receptors. Taste receptors are chemoreceptors; they send messages to the brain based on
the chemicals they detect. For humans to taste, food must be partially broken down in the
mouth and dry food must be mixed with saliva and dissolved in order for the molecules to
be able to fit into the taste pores and bind to the chemoreceptors (Gavin 2006). The
molecules are detected by the taste receptors and signals are sent to the brain with
information about what taste to perceive. Since dry foods must be dissolved by saliva in
order for the molecules to bond with the chemoreceptors reducing the amount of saliva
would reduce a person’s ability to distinguish between and taste different tastes. When
saliva is removed from a subjects tongue, he will suffer a decreased ability to detect taste
and will subsequently be unable to determine the difference between tastes of dry foods
such as salt and sugar.
The objective of this experiment was to determine if minimizing the amount of
saliva on the tongue effect ones ability to distinguish between sweet and salty tastes.
It was hypothesized that if saliva was removed from the mouth with a paper
towel, then subject would have a reduced ability to distinguish the difference between salt
and sugar.
Procedure:
The tests occurred between 8:40 am and 10:30 am in a classroom setting where
other students were participating in other experiments. The tests took place on February
11, 2008.
Subjects were selected at random from classes and areas around the school. Each subject
was between the ages of sixteen and eighteen years old and they were all males. The
subjects were brought one by one into the test area. They were seated in a chair with a
desk in front of it. On the desk were multiple pieces of paper towel and a small cup of
water. The subject was asked to take a sip from the cup of water and was then instructed
Differentiation between salt and sugar
to remove all of the saliva from their tongue using the paper towel. The subjects were
also instructed to keep their tongues out of their mouths so the tongue would stay dry.
The subject was then handed a cup 1 ml (± 0.1ml) of sugar and was instructed not to look
at the substance and was instructed to place a small amount on his tongue. Before the
subject pulled the tongue into his mouth he was asked what the substance on his tongue
tasted like. This information was then recorded on the table below. After the subject had
determined what he tasted he was instructed to take a sip of water and dry his tongue off
again. Then he was handed another cup, this time with 1 ml (± 0.1ml) of salt in it, and
was asked to repeat the procedure. This was done four more times, drinking and drying
off in between each taste. The pattern of tasting went as follows: sugar, salt, salt, salt,
sugar, sugar. After the tests in which the tongue was dried off were completed, the
subjects were asked to take a sip of water and were given 1 ml (± 0.1ml) of the
substances in the same order to see if they could tell the difference between the tastes
without their tongues dried off. They took a sip of water between each taste. Their
ability to tell the tastes without drying off their tongues was recorded. In this experiment
60ml of salt, 60ml of sugar, a 1ml measure, drinking water, and 30 paper cups were used.
A chi-squared test was done using the observed data to determine whether or not there
was a significant difference between tasting with or without drying off the tongue.
Result:
Overall, in the tests where saliva was removed from the subjects’ tongues, there
were twenty-eight incorrect perceived tastes and there were thirty-two correct perceived
tastes (Table 1). Of the thirty tongue-dried tests using sugar seventeen tests resulted in
incorrect perception of taste, while there were thirteen correct perceptions(Appendix A).
Of the thirty tongue-dried tests using salt, eleven were perceived incorrectly and nineteen
were perceived incorrectly (Appendix A).
Differentiation between salt and sugar
Table 1: Results of the total number of times the subjects detected the correct and
incorrect taste when they removed the saliva from their tongue.
Test
Test 1
Test 2
Test 3
Test 4
Test 5
Test 6
Taste
Sweet
Salty
Salty
Salty
Sweet
Sweet
Total
7 Wrong
3 Right
4 Wrong
6 Right
3 Wrong
7 Right
4 Wrong
6 Right
5 Wrong
5 Right
5 Wrong
5 Right
Of the thirty not-dried tests using sugar thirty were perceived correctly, and of the
thirty non-dried tests using salt thirty were perceived correctly as well (Table 2,
Appendix B).
Table 2: Results of the total number of times the subjects detected the correct and
incorrect taste when they tasted the substances with saliva.
Test
Test 1
Test 2
Test 3
Test 4
Test 5
Test 6
Taste
Sweet
Salty
Salty
Salty
Sweet
Sweet
Total
10 Right
10 Right
10 Right
10 Right
10 Right
10 Right
Chi-squared test to evaluate whether or not there is a significant difference in the
statistical data observed during the experiment:
X2 = ∑(Observed value – Expected value) 2
Expected Value
X2 = (13 – 30)2 + (19 – 30) 2
30
30
2
X = 13.66666….
X2 = 13.7
Degree of Freedom = possible out come - 1
Degree of Freedom = 2 - 1
Degree of Freedom = 1
Based on the Chi-squared calculations and the Chi-squared table there is a
significant difference in the two bodies of data.
Differentiation between salt and sugar
Discussion:
The chi-squared value of 13.67 and the degree of freedom of 1 results in a level of
probability of the observed values being merely by chance to be less than 0.0005 which
results in the rejection of the null hypothesis and the support of the hypothesis that
reducing the amount of saliva on the tongue results in a decreased ability to distinguish
between the two tastes. This supports the idea that saliva is needed to partially break
down and dissolve solid, dry food in order for humans to distinguish between and taste
certain, dry foods.
Even though the Chi-squared test supported the hypothesis that the reduction of saliva
will reduce a person’s ability to taste there were still errors in the procedure which could
have affected the results and created false support for the hypothesis. Some sources of
error include: the error of the measuring spoon used to measure the one milliliter of
substance each subject was given in each trial. Another source of error in this experiment
is there area of the tongue the salt or sugar was placed on. In most of the tests the sugar
or salt was placed on the middle to front of the tongue. This could change the results
because of the difference in heightened perception of specific tastes on different areas of
the tongue. The placement of the substance could have been effected by tongue length
because the subjects had varying tongue lengths and had so some would place the salt or
sugar farther back than others. Subjects 1, 2, 5 and 6 all had shorter tongues than the
other subjects. The drying of the tongue is another source of error because each subject
dried his own tongue because the administrator of the experiment did not want to touch
the tongues of the subjects. Since each boy dried his own tongue the degree to which the
tongue was dried could have varied. Some of them may have dried it off completely
getting underneath and on the sides, while others did not dry the sides. Subject 8 mostly
likely did not dry the sides of his tongue because he said that he could tell the taste when
the substance moved to the sides of his tongue. Along with the incomplete drying of the
tongue, this observation by subject 8 also suggests that movement could have been a
source of error. Some of the boys tested may have moved their tongues and been able to
taste the substance or feel how it moved and infer as to whether it was salt or sugar.
Also, even though the subjects were told not to look at the substances in the cups before
they put them on their tongues, some did observe what the substance in the cup looked
Differentiation between salt and sugar
like which could have affected their judgment of the taste. The amount of water between
each taste was not controlled so this too could have been a source of error.
If this experiment is carried out in the future, it should undergo a few changes.
The subjects should be blind folded so they cannot see the substance before it is placed
on the tongue, it would also be beneficial to place the substance in the same area each
time possibly by measuring from the tip. Another change that could be made in order to
improve the accuracy would be to measure the amount of water between each taste and
also to have the same person dry off the tongues in the same way, it would be best to
have the tongue drier wear gloves. The subjects could also be instructed to hold their
tongues still and could be selected to have similar tongue lengths.
One suggestion made by subject 3 would be to us more closely tasting substances
to test between because he said that the reason he could tell which was salt was from the
burning sensation he felt on his tongue. He believed that if the tastes were more neutral
and similar than he would not have been able to tell the difference between the two
substances.
Differentiation between salt and sugar
Literature Cited:
Gavin Mary (2006) Kids health. What’s spit. URL
http://www.kidshealth.org/kid/talk/yucky/spit.html. (Review: November 2006)
Ritter, B., Coombs, R. F., Drysdale, B. R., Gardner, G. A., Lunn, D. T. (1993). Biology
(Nelson), Scarborough, Ontario, Thomson Canada Limited.
NCIB, PubMed. http://www.ncbi.nlm.nih.gov/pubmed/2182682. Visited Feb. 11, 2008.
Differentiation between salt and sugar
Appendix A
Table A: Raw data of the number of times the subject detected the correct and incorrect
taste when they removed the saliva from their tongue.
Subject
Test 1
Test 2
Test 3
Test 4
Test 5
Test 6
Taste
Sweet
Salty
Salty
Salty
Sweet
Sweet
1
Wrong
Wrong
Right
Wrong
Right
Right
2
Right
Right
Right
Right
Wrong
Wrong
3
Wrong
Right
Wrong
Right
Right
Right
4
Wrong
Wrong
Wrong
Wrong
Wrong
Wrong
5
Right
Wrong
Right
Wrong
Wrong
Right
6
Wrong
Right
Right
Right
Wrong
Wrong
7
Wrong
Right
Right
Right
Right
Wrong
8
Right
Right
Right
Right
Right
Right
9
Wrong
Wrong
Wrong
Wrong
Wrong
Wrong
10
Wrong
Right
Right
Right
Right
Right
7 Wrong
4 Wrong
3 Wrong
4 Wrong
5 Wrong
5 Wrong
Total
3 Right
6 Right
7 Right
6 Right
5 Right
5 Right
Differentiation between salt and sugar
Appendix B
Table B: Raw data of the number the number of times the subjects detected the correct
and incorrect taste when they tasted the substances with saliva.
Subject
1
2
3
4
5
6
Taste
Sweet
Salty
Salty
Salty
Sweet
Sweet
1
Right
Right
Right
Right
Right
Right
2
Right
Right
Right
Right
Right
Right
3
Right
Right
Right
Right
Right
Right
4
Right
Right
Right
Right
Right
Right
5
Right
Right
Right
Right
Right
Right
6
Right
Right
Right
Right
Right
Right
7
Right
Right
Right
Right
Right
Right
8
Right
Right
Right
Right
Right
Right
9
Right
Right
Right
Right
Right
Right
10
Right
Right
Right
Right
Right
Right
10 Right
10 Right
10 Right
10 Right
10 Right
10 Right
Total