**Exclusion Criteria**
Subject data will be excluded on the following grounds:
* Subjects reported being under 18 years of age.
* Subjects reported problems with experimental playback, such as stuttering, freezing (pre-determined options) or another issue specified in a free-response.
* Subjects reported needing correction to their vision but not wearing it during the experiment.
* Subjects reported counts that err by more than 50% in either direction more than once.
* Subjects reported having performed a similar task before, wherein they tracked multiple objects and something unexpected appeared.
* Subjects failed to answer any question during the course of the experiment.
**Measures** <br>
After each trial in which no unexpected object appears and after the critical trial, we will collect subjects' counts of how many times the attended objects bounced off the edge of the frame.
On the critical trial, we will ask whether subjects noticed an extra object and then ask them to describe the shape and color from a menu of pre-determined options. Subjects will be counted as having noticed the object only if they affirm having seen something new and correctly identify either its shape, color, or both. <br>
We will also collect a set of demographic data for exclusion purposes, as well as characterizing our sample.
**Analysis** <br>
We will conduct two tests: one on the (notice vertical - notice horizontal) difference score in the attend rectangles condition, and one on the (notice vertical - notice horizontal) difference score on the attend circles condition.
For each test, we will determine the difference in noticing rates for each condition and will compute a 95% confidence interval around that difference to determine whether it includes 0.
If subjects noticed the less-similar unexpected object more often when attending to rectangles because of confusability between the matching unexpected object and the display objects, then making the unexpected object a unique color should generate the pattern of data expected under the similarity account: more similar objects should be noticed more often when they match the attended set, and less often when they match the ignored set. If we find the same results as before, it suggests that confusability does not drive this effect.
