Comparison Blindness

Change blindness has been linked to comparisons over time when visual input is disturbed by a transient. This is most directly seen in “flicker” paradigms where change is invisible when introduced during a blank period between successive presentations of stimuli, and is implicit in paradigms where a stimulus is changed during a saccade. Difficulties in comparing two simultaneously present stimuli have been considered to be due to transaccadic memory limitations in tasks requiring saccades. We present here experiments that demonstrate the phenomenology of change blindness, but in tasks where two stimuli are present in the central visual field within a single fixation and where there are no transients present. These experiments are based on contrast discriminations of patterns composed of a few simple elements. We have found comparisons over space within a single fixation to be as difficult as comparisons over time. As in the more usual paradigms for change blindness, cueing makes changes easy to detect. These results suggest that a memory bottleneck is not essential to produce change blindness.     

The illusory-letters phenomenon: an illustration of graphemic restoration in visual word recognition

We present a demonstration of word perception in which stimuli containing very few letters (just 50% of their original number) are presented for unlimited durations and yet are seen unequivocally as complete words. The phenomenon suggests that recognition of words can be achieved even when perception of their component letters is prevented.     

Assessing the importance of letter pairs in initial, exterior, and interior positions in reading

Exterior letter pairs (e.g., d--k in dark) play a major role in single-word recognition, but other research (D. Briihl & A. W. Inhoff, 1995) indicates no such role in reading text. This issue was examined by visually degrading letter pairs in three positions in words (initial, exterior, and interior) in text. Each degradation slowed reading rate compared with an undegraded control. However, whereas degrading initial and interior pairs slowed reading rate to a similar extent, degrading exterior pairs slowed reading rate most of all. Moreover, these effects were obtained when letter identities across pair positions varied naturally and when they were matched. The findings suggest that exterior letter pairs play a preferential role in reading, and candidates for this role are discussed.