In The Mismeasure of Man, biologist Stephen Jay Gould uses Morton’s original notes and raw data to evaluate his methods. Gould summarized Morton's inconsistencies and "finagling" into four general categories:

1. Morton’s sub-samples were not inclusive. For example, of the 333 skulls in his "American Indians" sample, 155 were Inca from South America. Their skulls tended to be smaller than those of other Indian groups. At the same time, he lumped the relatively larger Iroquois skulls into a separate category called "Barbarous Tribes." When he found that Indian skulls were smaller than other Caucasian skulls, he omitted them from his "Modern Caucasian" group.

2. Morton’s measurements were influenced by his subjective expectations. Morton used mustard seed to measure the cranial capacities of his skulls. Gould found that the seeds were often packed tightly in the European skulls but not in Indian or African American skulls. As a result, Morton inflated the sizes of European skulls and deflated those of other groups.

3. Morton failed to correct his figures for gender and stature. Since females tend to be smaller than males, they have smaller skulls. Morton included more female skulls in his African and Indian groups than in his European group. The result was to inflate the size of European skulls and decrease those of other groups.

4. Morton miscalculated some numbers and left out others. For example, he rounded down measurements for Egyptian skulls and rounded up measurements of German and Anglo-Saxon skulls.₁

Despite these errors, Gould does not think that Morton intended to deceive anyone. If that had been his intention, he probably would have tried to cover up his data and hide his procedures. What does Gould’s study suggest about the ways unconscious assumptions may affect one’s objectivity?