本文對社交網站傳遞的產品品質信號進行實證。我們以「朋友」和「讚」的線索來衡量它們對產品品質認知的影響，並同時研究熟悉度、認知風險和評論效價的調節作用。透過兩個Facebook實驗，我們首先比較了朋友、朋友的朋友、和廣告所提供的資訊之影響。結果表明，品質認知會受到社交信號的影響而帶來購買意願。「朋友」線索的影響受到熟悉度和風險的正向調節。然而，「讚」對品質認知的影響在不同的熟悉度和風險中沒有明顯的差異。接著，我們區分正面和負面評論以探討資訊效價的影響。結果顯示，在負面評論下，朋友和衍生朋友的線索所產生的信號之影響並沒有差異；「讚」的數量也是一樣的結果。亦即，對負面評論的評斷會遮蓋掉好友類型和評級數量的影響。

This study examines the signals of product quality transmitted on social network sites. We use the cues friend and like as measurements to determine their influence on perceived product quality and the moderating role of familiarity, perceived risk, and review valence. The hypotheses were tested using two Facebook field experiments. We first compared the effects of information provided by friends, friends of friends, and advertisements. The results indicate that social signals affect perceived product quality, which produces intentions to purchase. The effect of friend cues is positively moderated by perceived familiarity and risk. Nevertheless, like does not make a noticeable difference on perceived quality for varying perceived familiarity and risk. We then studied the effect of information valence by differentiating between positive and negative reviews. The results indicate that the power of signals produced by friends’ and derived friends’ cues does not differ under negative review situations; the same result was found for like volume. The judgment of negative reviews overshadows both friendship type and rating volume effects.