Date of Award


Degree Name

Doctor of Philosophy




Wendy S. Francis


Most research on visual object identification focus on the bottom-up processes of the visual what? and where? pathways. However, such research has not been able to fully account for many visual abilities (e.g., identifying an object among many other objects and across changing conditions). Neurological evidence has shown that feedback from high-level areas (i.e., top-down processing) makes object processing more efficient. However, there are no behavioral studies that have tested this. Thus, four experiments used a concurrent n-back task to occupy higher-level areas and tested its effects on visual object processing relative to a number-repetition control task.

Experiment 1 examined change detection in a flickering task, in which two versions of a picture alternated rapidly with an intervening mask. Concurrent performance of the n-back task reduced the ability to detect changes relative to the concurrent control task. Experiments 2, 3, and 4 examined the identification of pictures that were presented briefly (50, 100, or 500 ms). Overall, there were more errors and longer response times when a concurrent n-back task was performed relative to the control task. With shorter presentation times, identification was less accurate and more adversely affected by the n-back task. Experiment 3 examined short-term priming of object identification in picture naming based on a briefly presented prime picture. Short-term repetition priming effects were reliable but reduced when a concurrent n-back task was performed, but priming was not affected by prime presentation time. Experiment 4 examined long-term priming of object identification based on a briefly presented prime picture. Although the concurrent task effect indicated slower test-phase picture-naming responses for the n-back condition, this result was inconclusive given that none of the priming effects were statistically significant.

The results suggest that top-down processes affect object processing in terms of attention, which is essential to store and maintain information in working memory. It is also suggested that attention plays an important role in facilitating the process of object recognition. In terms of repetition priming, the present study confirmed the involvement of top-down processes in short-term and long-term priming effects.




Received from ProQuest

File Size

88 pages

File Format


Rights Holder

Gabriela Durán