成人辨識自己種族臉孔的能力較好，而辨識其他種族臉孔的能力較差，此現象稱為「他種族效應」。Kelly等人（2007b；2009）發現三個月大的小嬰兒可以區辨自己種族和其他種族的臉孔，但是到了九個月大僅只能區辨自己種族的臉孔；研究者認為可以用「知覺窄化」的概念加以解釋。然而目前關於嬰兒期「他種族效應」的主要發現僅證明嬰兒辨識其他種族臉孔的能力隨著年齡增長而變差，缺乏研究證據同時探討嬰兒辨識自己種族臉孔的能力是否會進步。
因此，本研究主要目的乃透過操弄不同難易程度的臉孔刺激圖片，來探討台灣地區四個月大、六個月大和九個月大的小嬰兒辨識自己種族臉孔的能力是否會隨著年齡增長而有所變化；同時也探討成人對於自己種族和其他種族臉孔區辨力的表現，如此除了可以證明刺激難易度的操弄之有效性，亦可藉此得到參照值並佐證台灣成人的「他種族效應」。本研究利用「視覺刺激配對比較法」，先呈現單張臉孔圖片讓受試者熟悉化，接著再呈現一組臉孔配對圖片讓受試者觀看，是為一次嘗試。在這一組臉孔配對圖片中，其中一張是和熟悉化相同的臉孔，另一張則是不同難易程度的臉孔。簡單程度是換上另一張不同的人臉，中等程度是改變同一張臉孔的一個特徵（眼睛）和空間位置（口鼻距），困難程度則是僅改變一個空間位置；在成人實驗中，另有「相同程度」的操弄，亦即兩張臉孔皆相同。
嬰兒實驗結果顯示四個月大的小嬰兒僅能區辨亞洲人簡單程度的臉孔，六個月大的小嬰兒可以區辨亞洲人、白種人和黑種人簡單程度的臉孔，九個月大的小嬰兒表現最好，除了可以區辨所有簡單程度的臉孔，更可以區辨亞洲人和白種人中等程度的臉孔。成人實驗結果證明刺激難易度的操弄是有效的，且受試者在判斷自己種族中等程度臉孔時，其正確率顯著高於判斷其他種族中等程度臉孔；而反應時間也較判斷其他種族臉孔的時間要來的短。整體而言，有別於先前研究所看到的知覺窄化現象，本研究發現小嬰兒辨識臉孔的能力會隨著年齡增長而變得更好，且辨識自己種族臉孔的能力看起來會最早出現；而辨認其他種族的能力（如黑種人）並不會消失，僅是維持在最基本的辨識層次上。
Human adults can discriminate own-race faces better than other-race faces (Meissner & Brigham, 2001). This phenomenon is referred to as the other-race effect (ORE). An early onset of ORE has been observed in Caucasian infants (Sangrigoli & de Schonen, 2004b; Kelly et al., 2005). Our purpose was to study the face processing ability for own- and other-race faces in Taiwanese infants aged between 4 and 9 months when the visual system is still maturing. The stimuli contained faces of three ethnic groups (Asian, Caucasian, and African). In each race, the face discrimination task had three levels of difficulty (Easy: change identity, Median: change one feature and one spacing, and Hard: change one spacing only). Infant experiment adopted the visual paired-comparison (VPC) task to assess 4-, 6-, and 9-month-old infants’ discriminability for the familiar/novel faces via recording infant’s looking preference (fixation time). Adult experiment was intended to offer a performance reference, which was conducted in comparable fashion except that an additional “identical” condition (two identical faces in the test phase) was added. The results showed that 4-month olds can only discriminate Asian “easy” faces. 6-month olds can discriminate “easy” faces of all three ethnic groups. 9-month olds can further discriminate “median” Asian and Caucasian faces but not African “median” faces. Adults’ accuracy decreased and response time increased as the stimulus difficulty increased, indicating the validity of the stimulus difficulty. In conclusion, own-race advantage emerges around 4 months of age, while ORE may take place between 6 and 9 months as the discriminability for African faces does not improve. Taken together, these findings suggest a mixture of general improvement in face processing ability as well as a specific tuning by the own-race experience.
