Abstract
Car and face expertise are similar because they both engage holistic processing and they also compete with each other when objects from both categories are processed simultaneously. Competition occurs across a variety of tasks (visual search, discrimination in rapid visual streams, working memory tasks) and regardless of whether car distractors are task-relevant or not. Here, we investigate competition in an ensemble coding task. The relationship between single object recognition and ensemble coding is debated, but if ensemble coding relies on the same ability as object recognition, we expect cars to interfere with ensemble coding of faces as a function of car expertise. We measured 53 participants’ ability to make judgments of variability about arrays of faces, in the presence of car or novel object distractors (called Ziggerins). On each trial, participants viewed two sequentially presented arrays of 4 faces and 4 distractors, judging which array had the more diverse faces regardless of distractors. Face-diverse arrays included 4 faces from different people while Face-repeated arrays included 4 faces of 2 different people. The distractors were 4 different cars or 4 different Ziggerins. We measured car expertise with the Cambridge Car Memory Test and the Vanderbilt Car Matching Test. We also measured object recognition ability with novel objects with a Matching Task and with the Novel Object Memory Test and face recognition ability with the Cambridge Face Memory Test. Ensemble coding performance with faces was strongly correlated across the two distractor conditions. Critically, we found evidence against competition as a function of car expertise during ensemble coding of faces, using both a difference score (r=-.10, BF10=.22) or a regression approach (r=-.07, BF10=.19) to index competition. The results suggest that ensemble coding, unlike single object recognition, is not susceptible to competition between different domains of similar expertise.