Experimental results.

<p>Threshold change ratios for the three main conditions are computed by dividing the contrast threshold in each case with the corresponding baseline threshold, such that a value of one indicates no effect of adaptation. Values below one represent lowered thresholds, i.e., a facilitation effect, and values above one represent elevated thresholds, i.e., a suppression effect. Geometric averages across nine subjects are shown. Adapting to the same face as the test face lowered thresholds below baseline performance, and adapting to a different face elevated thresholds. Most importantly, adapting to a different face elevated thresholds even more if it also differed in gender from the test face. Stars represent significant pair-wise differences. Errorbars are 68% bootstrap confidence intervals.</p

Hypothetical model predictions for magnitude of figural aftereffects in same-gender, cross-gender and gender-contingent conditions based on proximity in face space.

<p>(A) Effects of adaptation are dependent on the similarity between the adapting and test stimuli. Perceptual aftereffects peak at a neighboring location, then gradually fall off as the test stimuli become more dissimilar. For example, the effect of adapting to a contracted female face will have greater impact on a female test face (red curve, ‘a’) than a male test face (red curve, ‘d’) simply due to greater similarity between faces of the same gender compared to faces of different genders. The result is cross-gender transfer of aftereffects (‘d’) that is less than the aftereffect for the same-face (‘a’). The same logic applies to the effects of adapting to an expanded male face (blue curve). (B) Gender-contingent aftereffects are obtained by simultaneously adapting to a male and a female face with opposing figural distortions. The fact that contingent aftereffects are usually found to be smaller in magnitude than same-gender aftereffects are predicted by an additive effect of the simultaneous adaptation: Adapting to a contracted female face generates a large perceptual bias on a female test face (red curve, ‘a’), which is offset by a smaller but opposite bias caused by adapting to an expanded male face (blue curve, ‘b’). Thus the contingent aftereffect magnitude ‘c’ will be equivalent to the same-gender aftereffect ‘<i>a</i>’ reduced by the cross-gender aftereffect ‘b’.</p

Illustration of a typical trial.

<p>Each trial starts with a 100-ms adapting period during which either one of four faces (two females and two males) or a blank stimulus is shown. Following this is a 50-ms noise mask, a 150-ms fixation cross, and a 150-ms blank. After this a test face is shown for 150 ms. The test face is randomly chosen from the same set of four faces that were used as adapting stimuli. The task of the subject is to indicate which one of the four test faces they saw by choosing it from a choice display that remained until the subject entered their response. Contrast thresholds were measured for recognizing each face in a 4-alternative forced-choice (4-AFC) paradigm. A psychophysical staircase controls the contrast of the test face at each trial to estimate thresholds for 82% accuracy. The adapting faces are shown at a fixed rms contrast of 60%. The 20 adapting/test stimulus pairs (five adapt×four test) were further classified into three main conditions: (1) <i>the same-face condition</i>, where the test and adapting faces were the same, (2) <i>the same-gender condition</i>, where they were different faces of the same gender, (3) <i>the different-gender condition</i>, where they were different faces of different genders, in addition to <i>the baseline condition</i>, where the adapting stimulus was a blank.</p