We parsimoniously model the effect of proactive interference and memorization effort in learning stable graphical layouts. We model the visual search cost, i.e. the number of distractors visually encoded while looking for a target item, as a reasonable surrogate of onscreen proactive interference. Further, we show that a novel quantity that we term "effort factor" is an acceptable estimate for comparing the memorization effort across different access cost of onscreen information during the early stages of practice.