Abstract
Boundary extension (BE) is a memory error in which people recall seeing more of a scene than was viewed. A few recent studies challenged this effect as an artifact of particular types of pictures. This study used two pictures sets, one including a diverse set of pictures (Set 1) and another set including more close-up pictures similar to many previous BE studies (Set 2). Two experiments tested the effect of varying presentation times (1.5 s v. 15 s) and picture set size (15 v. 30 pictures) on BE. In Experiment 1, participants viewed either 30 or 15 pictures, from Set 1 or Set 2, for 1.5s each. Afterwards, the same scenes were presented with random initial expanse, participants adjusted the boundaries to match their memory (boundary adjustment test.) Significant BE was obtained in all conditions. There was no significant effect of picture set. An analysis done only on the first 15 pictures in the 30-picture condition revealed no significant effect of set size. Individual picture analysis showed either BE or no significant distortion. No pictures showed significant boundary restriction. In Experiment 2, participants viewed 30 pictures (Set 1 or Set 2) for either 1.5s or 15s. A secondary people search task was done during the presentation. Participants completed the boundary adjustment test. Again, Boundary Extension was obtained for both picture sets, with no significant difference. Moreover, the presentation rate didn’t affect BE. Individual picture analysis showed a systematic pattern of BE. One picture in Set 1 did show significant restriction. However, the other 59 pictures showed either significant extension or no significant directional distortion. These results support the robustness of the BE effect and indicate no significant variations due to picture set, set size and presentation times, in the ranges tested here. Future research should test larger ranges.