Jean Piaget was a scientist who in the early to mid 1900's studied the tendency to focus attention on only one characteristic of shape. In particular, he studied the human inability to distinguish identical volumes in different sized containers.
Piaget studied the inability of small children to understand that cylinders with different aspect ratios could have the same volume. Small children have difficulty conceiving the shift in volume from one dimension (say the width of a glass) to another dimension (say the height of a glass). They have difficulty visualizing that there is no more liquid in a tall, slender glass than in the shorter, wider glass. He showed that for certain individuals, this tendency could extend into adulthood.
This is illustrated in the following Figure:
The tendency is to believe that even though the two glasses have the same volume, the tall, slender glass has more volume because the height of the liquid is greater.
This fact explains why studies show that mixed drinks at bars that use short, wide glasses are typically stronger then the same drink at bars that use tall, slender glasses (see study). The height of a 1.5 oz. shot of alcohol in the short, wide glass is not as high as the same 1.5 oz. shot in the tall, slender glass. When bartenders pour a shot in a short, wide glass they have the tendency to think that since the liquid level is not very high they have mis-poured, and so add a little more alcohol to the drink. The moral of this study is always get your mixed drink from bars that use short, wide glasses.
This misconception of relative volume is what leads us to think that the relatively small top portion of a pint glass could not contain such a large percentage of the total volume. In fact, if beer is poured into a pint glass to about 1/2 inch from the top, 13% of the beer is GONE. A pour to about an inch from the top of the glass leaves out 25% of the beer. This is illustrated below, where the "Beer Gauge" is used to indicate the amount of beer missing from the pint glass.
Figure 1: 13 % missing from the pint. Figure 2: 25 % missing from the pint.
Keep your bartender honest and Order your very own "Beer Gauge" today (Order Information).
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