Abstract
According to Kirchner and Thorpe (2006), it takes less than 120 ms to detect the presence of an animal in peripheral vision. Here we investigated whether the same applies to a very different kind of visual object: printed words. Using their forced-choice saccade paradigm, we measured the time to initiate a saccade to target stimuli presented in peripheral vision (6° left or right of a central fixation mark). Targets were pictures of animals in one block and 5-letter words in another block. Targets were accompanied by distractor stimuli in the contra-lateral visual field, which were visual scenes without animals for animal targets, and random strings of consonants for word targets. To limit differences between words and images and compensate for the visual acuity decrease in peripheral vision, we used large words (about 1.7° per letter). Targets were also presented without contra-lateral stimuli in a control condition. Although saccade latencies did not differ across words and animals in the control condition, we found that animal detection was faster and more accurate than word detection. The estimated fastest latencies of saccades to the target were 140 ms and 200 ms respectively for animal and word targets. The results for animal targets replicate those reported by Kirchner and Thorpe (2006). The timing found for word targets shows that word identification processes require more time. Within 200 ms, combinations of letters can be processed and can direct eye movements to the target words even if word identification is not complete. This is in line with estimated time-course of visual word recognition derived from ERP studies of foveal word recognition (Grainger & Holcomb, 2009). Our findings raise the possibility that words are processed by mechanisms that have adapted to the specific constraints imposed by printed words compared with other types of visual object.
European Research Council.