Time course of visual object categorization: Fastest does not necessarily mean first

Perceptual categorization at the basic level is generally faster than categorization at more superordinate or subordinate level [Rosch, E., Mervis, C. B., Gray, W. D., Johnson, D. M., & Boyes-Braem, P. (1976). Basic objects in natural categories. Cognitive Psychology, 8(3), 382-439]. But, what does it mean to be fastest? One possibility is that levels of abstraction that are categorized fastest are processed first. In this vein, the basic level is often considered the "entry level" into our knowledge about categories in the world [Jolicoeur, P., Gluck, M. A., & Kosslyn, S. M. (1984). Pictures and names: Making the connection. Cognitive Psychology, 16(2), 243-275]. We tested this "fastest means first" hypothesis by contrasting the time course of basic- and subordinate-level categorization of objects in a signal-to-respond experiment. This method probes subjects to respond at systematically varying points in time after the onset of the object. The time course function relating performance to time is characterized by its onset, growth rate, and asymptote. While basic and subordinate categorization differed significantly in growth rate and asymptote, they did not differ significantly in onset. If a basic-level stage preceded a subordinate-level stage, we should have observed a difference in onset. We conclude that fastest does not necessarily mean first in perceptual categorization.