Postdiscrimination Gradients With Familiar and Unfamiliar Faces

Abstract

Discrimination training is often used to improve accuracy in stimulus recognition. However, intradimensional discrimination training with a single positive exemplar and a single negative exemplar may reduce accuracy during a generalization test. More specifically, discrimination training can cause a shift in responding from the positive exemplar to stimuli unlike the negative exemplar. Previous studies have shown that the length of discrimination training affects the degree to which a shift occurs. We sought to determine whether pre-experimental exposure ("familiarity") to the stimuli would have a similar effect. Twenty participants were trained and tested with two different sets of facial images. Each set of images consisted of stimuli that ranged from the naturally asymmetrical version of the face to a symmetrical version of the face. In one condition, the images were based on the participant's own face; in the second condition, the images were based on the face of a stranger. In both cases, the median face served as the positive exemplar. In half of the conditions the naturally asymmetrical face served as the negative exemplar, and in the other half, the symmetrical face served as the negative exemplar. Images based on a stranger's face produced greater generalization than images based on the participant's own face. A significant gradient shift occurred only with familiar faces.

A jump to the left and a step to the right: A test of two accounts of peak shift

“…Given these assumptions, it is possible to make quantitative predictions about the effects of different combinations of stimuli on adaptation level that allow different predictions about the shape of generalization gradients from ALT. Peak shift has been shown to be a general and robust effect that has been demonstrated across multiple dimensions including; faces (e.g., Derenne 2010;Derenne, Loshek & Bohrer, 2015;Spetch, Cheng, & Clifford, 2004), face caricatures (Lewis, 1999), line angles (Bloomfield, 1967;Thomas, Mood, Morrison, & Wiertelak, 1991), spatial location (Cheng & Spetch, 2002;Cheng, Spetch, & Johnston, 1997), and wavelengths of light (Thomas, Windell, Williams, & White, 1985). Furthermore, peak shift has been demonstrated across multiple species including: chickens (Rudolph & Honig, 1972), goldfish (Ames & Yarczower, 1965), guinea pigs (Thomas & Setzer, 1972), horses (Dougherty & Lewis, 1991), monkeys (Moody, Stebbins, & Iglauer, 1971), pigeons (Hanson, 1959), and rats (Thomas & Setzer, 1972), as well as humans (e.g., Derenne 2010; Lewis, 1999;Spetch et al, 2004;Thomas, et al, 1991).…”

“…Peak shift is also affected by the range of stimuli used during training and testing (e.g., Derenne, 2006;Derenne, 2019;Derenne et al, 2015;McLaren & Mackintosh, 2000;Wisniewski, Church, & Mercado, 2009), and if the stimuli are arranged simultaneously or successively (Derenne & Garnett, 2016). It is from experiments that have manipulated the relative positions of the S+ and S-that the most convincing evidence supporting ALT has been reported.…”