• Marco Tommasi
  • Silvia Errico


Many psychophysical experiments showed that subjective judgments are affected the frequency of stimulus presentation. Skewing in frequency distributions of stimulus presentation produces a shift in subjective scales of stimulus intensities. This bias is called Frequency Effect. However, no research was carried on to test if Frequency Effect can bias responses obtained in tests or questionnaires. In our research, we asked participants to indicate the correct capital city of a specific country and to judge how much difficult is the item, as well. The test was composed by 30 items, part of them with low, medium or high level of difficulty. We also presented participants three different forms of the test: a form wherein the easy items where more frequent; a form wherein the items with an intermediate level of difficulty were more frequent; a form wherein the difficult items were more frequent. Results showed that subjective judgments of item difficulty were affected by the form of the test. When difficult items are more frequent, participants respond more accurately and rate items as less difficult.

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