Salient object changes influence overt attentional prioritization and object-based targeting in natural scenes

Abstract

A change to an object in natural scenes attracts attention when it occurs during a fixation. However, when a change occurs during a saccade, and is masked by saccadic suppression, it typically does not capture the gaze in a bottom-up manner. In the present work, we investigated how the type and direction of salient changes to objects affect the prioritization and targeting of objects in natural scenes. We asked observers to look around a scene in preparation for a later memory test. After a period of time, an object in the scene was increased or decreased in salience either during a fixation (with a transient signal) or during a saccade (without transient signal), or it was not changed at all. Changes that were made during a fixation attracted the eyes both when the change involved an increase and a decrease in salience. However, changes that were made during a saccade only captured the eyes when the change was an increase in salience, relative to the baseline no-change condition. These results suggest that the prioritization of object changes can be influenced by the underlying salience of the changed object. In addition, object changes that occurred with a transient signal (which is itself a salient signal) resulted in more central object targeting. Taken together, our results suggest that salient signals in a natural scene are an important component in both object prioritization and targeting in natural scene viewing, insofar as they align with object locations.

Fig 1. Example image with the selected object outlined in white (not shown during experiment).

The critical object is increased in luminance (A), unaltered (B), and reduced in luminance (C).

Fig 2. The mean proportion difference from baseline that landed within the bounding box region of the critical object.

(A) For Trial type, Fixation index, and Direction of change. Individual subject mean proportion differences are plotted in lighter shaded points. (B) Baseline object viewing rates. Error bars represent confidence intervals corrected for between-subjects variance [44,45].

Fig 3. 2D density plots of the normalized landing position of the first fixation into the object across Trial type and Direction of change.

Density estimation for this and subsequent plots performed in ggplot2 [46] based on the R function kde2d [47].

Fig 4. 2D density plots of the normalized landing position of the first fixation into the object for fixation trials.

Split into two groups: the first fixation into the object was the first fixation after the change (left) and when the first fixation that landed on the object was later on in the trial (right).