★ We modified classification image technique working fine with fewer trials than ever. ★ The technique was applied to autistic individuals to show face-processing strategy. ★ We showed unexpected autistic observer’s face-processing strategy on forehead.
In the present study we modified the standard classification image method by subsampling visual stimuli to provide us with a technique capable of examining an individual’s face-processing strategy in detail with fewer trials. Experiment 1 confirmed that one testing session (1450 trials) was sufficient to produce classification images that were qualitatively similar to those obtained previously with 10,000 trials (Sekuler et al., 2004). Experiment 2 used this method to compare classification images obtained from observers with autism spectrum disorders (ASD) and typically-developing (TD) observers. As was found in Experiment 1, classification images obtained from TD observers suggested that they all discriminated faces based on information conveyed by pixels in the eyes/brow region. In contrast, classification images obtained from ASD observers suggested that they used different perceptual strategies: three out of five ASD observers used a typical strategy of making use of information in the eye/brow region, but two used an atypical strategy that relied on information in the forehead region. The advantage of using the response classification technique is that there is no restriction to specific theoretical perspectives or a priori hypotheses, which enabled us to see unexpected strategies, like ASD’s forehead strategy, and thus showed this technique is particularly useful in the examination of special populations.