How can you prefer one of two identical items?

𝗦𝗲𝗻𝘀𝗼𝗿𝘆 𝘀𝗰𝗶𝗲𝗻𝗰𝗲 would go nowhere 𝘄𝗶𝘁𝗵𝗼𝘂𝘁 𝗽𝘀𝘆𝗰𝗵𝗼𝗹𝗼𝗴𝘆. I am often reminded that some basic principles involving psychological components can appear 𝗰𝗼𝘂𝗻𝘁𝗲𝗿𝗶𝗻𝘁𝘂𝗶𝘁𝗶𝘃𝗲 to many, especially for those new to our field.

𝗖𝗮𝘀𝗲 𝗶𝗻 𝗵𝗮𝗻𝗱: How to interpret the preference choices in a 𝗯𝗹𝗶𝗻𝗱 preference test with a ‘No preference’ option? What if the two items are 𝗽𝘂𝘁𝗮𝘁𝗶𝘃𝗲𝗹𝘆 𝗶𝗱𝗲𝗻𝘁𝗶𝗰𝗮𝗹?

🟰 𝗔𝗻 𝗼𝗯𝘃𝗶𝗼𝘂𝘀 𝗮𝗻𝘀𝘄𝗲𝗿

When I ask students what results they would expect from this question:

• Prefer one of the two: 0%

• 𝗡𝗼 𝗽𝗿𝗲𝗳𝗲𝗿𝗲𝗻𝗰𝗲: 𝟭𝟬𝟬%

⁉️ 𝗔𝗻 𝘂𝗻𝗲𝘅𝗽𝗲𝗰𝘁𝗲𝗱 𝗼𝘂𝘁𝗰𝗼𝗺𝗲

As many of you are aware, the 𝗮𝗰𝘁𝘂𝗮𝗹 outcome will be much closer to:

• Prefer one of the two: 80%

• 𝗡𝗼 𝗽𝗿𝗲𝗳𝗲𝗿𝗲𝗻𝗰𝗲: 𝟮𝟬%

This clearly challenges the meaning of ‘prefer one of the two’ and how such results should be interpreted.

𝗧𝘄𝗼 𝗺𝗮𝗶𝗻 𝗱𝗿𝗶𝘃𝗲𝗿𝘀 𝗳𝗼𝗿 𝘁𝗵𝗶𝘀 𝘂𝗻𝗲𝘅𝗽𝗲𝗰𝘁𝗲𝗱 𝗼𝘂𝘁𝗰𝗼𝗺𝗲

- 𝗥𝗲𝘀𝗽𝗼𝗻𝘀𝗲 𝗯𝗶𝗮𝘀: The subject feels a subconscious drive to ‘pick a winner.’

- 𝗠𝗼𝗺𝗲𝗻𝘁𝗮𝗿𝘆 𝗽𝗲𝗿𝗰𝗲𝗽𝘁𝘂𝗮𝗹 𝘃𝗮𝗿𝗶𝗮𝗯𝗶𝗹𝗶𝘁𝘆, cornerstone of the Thurstonian/Signal Detection Theory frameworks. Our senses are noisy and no two momentary perceptions 𝘄𝗶𝗹𝗹 𝗲𝘃𝗲𝗿 𝗯𝗲 𝘁𝗿𝘂𝗹𝘆 𝗶𝗱𝗲𝗻𝘁𝗶𝗰𝗮𝗹.

𝗧𝗵𝗲 𝗻𝗲𝗲𝗱 𝗳𝗼𝗿 𝘀𝗽𝗲𝗰𝗶𝗮𝗹𝗶𝘇𝗲𝗱 𝗮𝗻𝗮𝗹𝘆𝘁𝗶𝗰𝗮𝗹 𝗮𝗽𝗽𝗿𝗼𝗮𝗰𝗵𝗲𝘀 𝗶𝗻𝗰𝗼𝗿𝗽𝗼𝗿𝗮𝘁𝗶𝗻𝗴 𝗿𝗲𝘀𝗽𝗼𝗻𝘀𝗲 𝗯𝗶𝗮𝘀

- 📊Use 𝗶𝗱𝗲𝗻𝘁𝗶𝗰𝗮𝗹𝗶𝘁𝘆 𝗻𝗼𝗿𝗺𝘀 (expected score distribution for identical samples)

- 🧠Apply 𝗽𝘀𝘆𝗰𝗵𝗼𝗹𝗼𝗴𝗶𝗰𝗮𝗹 𝗺𝗼𝗱𝗲𝗹𝘀 such as the Thurstonian 2-Alternative Choice

Statistics alone 𝘄𝗼𝘂𝗹𝗱𝗻’𝘁 𝗯𝗲 𝗮𝗯𝗹𝗲 𝘁𝗼 𝗵𝗮𝗻𝗱𝗹𝗲 this scenario, just as they can’t handle the 𝘂𝗻𝗲𝗾𝘂𝗮𝗹 𝗺𝗲𝗻𝘁𝗮𝗹 𝘀𝗽𝗮𝗰𝗶𝗻𝗴 of categories on rating scales or 𝗲𝘅𝗽𝗹𝗮𝗶𝗻 𝘁𝗵𝗲 𝗵𝗶𝗴𝗵𝗲𝗿 𝗽𝗼𝘄𝗲𝗿 of the 3-AFC and tetrad methods over the triangle test.

📄 For a recent publication listing many relevant references (𝗿𝗲𝗾𝘂𝗲𝘀𝘁 𝗼𝗻 𝗼𝘂𝗿 𝘄𝗲𝗯𝘀𝗶𝘁𝗲): Biases in paired preference tests: Cross-cultural comparisons of Japanese and American consumers. 2019. Yuka Hasegawa 𝘦𝘵 𝘢𝘭. Journal of Sensory Studies.

• 🎯Do you have go-to approaches to handling 𝗯𝗶𝗮𝘀𝗲𝘀 in 𝗽𝗿𝗲𝗳𝗲𝗿𝗲𝗻𝗰𝗲 𝘁𝗲𝘀𝘁𝘀?

• 💡Also, what 𝗼𝘁𝗵𝗲𝗿 𝗰𝗼𝗻𝗰𝗲𝗽𝘁𝘀 of sensory science do you know can be 𝗽𝗲𝗿𝗽𝗹𝗲𝘅𝗶𝗻𝗴 to students/professionals not -yet- versed in the intricacies of our field?