Attentional limits on the perception and memory of visual information

Palmer, J. (1990). Attentional limits on the perception and memory of visual information. Journal of Experimental Psychology: Human Perception and Performance, 16(2), 332-350.

Abstract:
Attentional limits on perception and memory were measured by the decline in performance with increasing numbers of objects in a display. Multiple objects were presented to Ss who discriminated visual attributes. In a representative condition, 4 lines were briefly presented followed by a single line in 1 of the same locations. Ss were required to judge if the single line in the 2nd display was longer or shorter than the line in the corresponding location of the 1st display. The length difference threshold was calculated as a function of the number of objects. The difference thresholds doubled when the number of objects was increased from 1 to 4. This effect was generalized in several ways, and nonattentional explanations were ruled out. Further analyses showed that the attentional processes must share information from at least 4 objects and can be described by a simple model.

Note:
A partial discrimination paradigm was used. This paradigm was like the single probe change detection paradigm. After a study display of 1 to 4 stimuli, a single test probe was presented at one of the locations. Participants were asked to judge if the probe was the same as the study item.

A set-size effect was observed with an increase of detection threshold as a function of the display set size. Palmer ruled out the possibility of sensory limitation by controlling the eye movement, configuration effect (solution: cued item was presented in the center as the single probe. As a result, the configuration information was excluded. The set-size effect was still observed.) The psychometric function was tested in Exp 2. the function shifted to the right as the set-size increased with similar shape. The set-size effect can be applied to different features such as size, and orientation (Exp 3). This effect was also resistant to the variation of the retention interval (Exp 4 for 0.5 s, Exp 1 for 2 s).

The sensory hypothesis was ruled out in Exp 5. Results showed the relevant set-size could account for the set-size effect. Exp 6 further demonstrated the effect o attention. Even when the set-size was four, performance with a cue was equal to that of set-size two. Exp 7 demonstrated uncured information is less well processed.

These results ruled out the sensory hypothesis, and decision hypothesis (This result is slight different from Palmer (1995), But the tasks were totally different: visual search vs. partial discrimination task). Results supported that attention plays a role in perception and memory.