Enhancement and Suppression Flexibly Guide Attention

Previous research suggests that observers can suppress salient-but-irrelevant stimuli in a top-down manner. However, one question left unresolved is whether such suppression is, in fact, solely due to distractor-feature suppression or whether it instead also reflects some degree of target-feature enhancement. The present study ( N = 60) addressed this issue. On search trials (70% of trials), participants searched for a shape target when an irrelevant color singleton was either present or absent; performance was better when a color singleton was present. On interleaved probe trials (30% of trials), participants searched for a letter target. Responses were faster for the letter on a target-colored item than on a neutral-colored item, whereas responses were slower for the letter on a distractor-colored item than on a neutral-colored item. The results demonstrate that target-feature enhancement and distractor-feature suppression contribute to attentional guidance independently; enhancement and suppression flexibly guide attention as the occasion demands.

Reading Ability and Attention to Words and Letters in Words

Students in grades 2, 4, and 6 were tested in two blocks of visual comparison trials. In one block, the primary task was to decide whether two words matched, and in the other block the task was to decide whether a single letter target matched the first letter of a word. On some trials in both blocks, the word comparison item was omitted and subjects were to decide whether a “7” occurred in the replacement display. On those probe trials, the “7” occurred either to the left or right of the display. In all grades, latencies for the primary task were faster for whole-word than for first-letter decisions. On the probe trials, latencies were faster when the probe item appeared in the first position of the display, but only in the block of first-letter trials. Moreover, the first-position advantage on probe trials was greater for good than for poor readers. The results were interpreted to be consistent with the hypothesis that both good and poor readers process words holistically. Poor readers are not more likely than good readers to attend to single-letter units in visual memory (cf. LaBerge & Samuels, 1974). Rather, poor readers are deficient in analyzing a word's components (cf. Wolford & Fowler, 1984).

On the Disruption of Visual Memory: Interference Produced by Visual Report Cues

Report of single letters from centrally-fixated, seven-letter, target rows was probed by either auditory or visual cues. The target rows were presented for 100 ms, and the report cues were single digits which indicated the spatial location of a letter. In three separate experiments, report was always better with the auditory cues. The advantage for the auditory cues was maintained both when target rows were masked by a patterned stimulus and when the auditory cues were presented 500 ms later than comparable visual cues. The results indicate that visual cues produce modality-specific interference which operates at a level of processing beyond iconic representation.