Scene Gist Categorization by Pigeons

Scene gist categorization in humans is rapid, accurate, and tuned to the statistical regularities in the visual world. However, no studies have investigated whether scene gist categorization is a general process shared across species, or whether it may be influenced by species-specific adaptive specializations relying on specific low-level scene statistical regularities of the environment. Although pigeons form many types of categorical judgments, little research has examined pigeons' scene categorization, and no studies have examined pigeons' ability to do so rapidly. In Experiment 1, pigeons were trained to discriminate between either 2 basic-level categories (beach vs. mountain) or a superordinate-level natural versus a manmade scene category distinction (beach vs. street). The birds learned both tasks to a high degree of accuracy and transferred their discrimination to novel images. Furthermore, the pigeons successfully discriminated stimuli presented in the 0.2- to 0.35-s duration range. Therefore, pigeons, a highly divergent species from humans, are also capable of rapid scene categorization, but they require longer stimulus durations than humans. Experiment 2 examined whether pigeons make use of complex statistical regularities during scene gist categorization across multiple viewpoints. Pigeons were trained with the 2 natural categories from Experiment 1 (beach vs. mountain) with zenith (90 degrees), bird's eye (45 degrees), and terrestrial (0 degrees) viewpoints. A sizable portion of the variability in pigeon categorization performance was explained by the systematic variation in scene category-specific statistical regularities, as with humans. Thus, rapid scene categorization is a process that is shared across pigeons and humans, but shows a degree of adaptive specialization.