Center-surround or spreading inhibition: which mechanism caused the negative effect from repeated masked semantic primes?

In the paradigm of repeated masked semantic priming (Wentura & Frings. 2005), prime and mask are repeatedly and rapidly interchanged. Using this technique in a semantic priming task with category labels as primes and category exemplars as targets (related, e.g.. BIRD - swan --> BIRD - finch; unrelated, e.g., BIRD - lily --> FRUIT - finch), Wentura and Frings found a negatively signed priming effect. Here we used the repeated masking technique with category exemplars as targets and primes (i.e., identity priming) for analyzing, whether this effect reflects center-surround or spreading inhibition. If the repeated masked technique reflects spreading inhibition, a negative effect should also appear for identity priming. In contrast, a center-surround approach would predict a positive effect. In accordance with the latter hypothesis, we found a significant positive effect in identity priming (Experiment 1a) and significant difference to the negatively signed semantic priming effect when primes were category labels (Experiment 1b). This is indicative of the repeated masked semantic priming effect being a negatively signed semantic priming effect due to a center-surround mechanism.