icient for detecting rotation because the detectors would be unable to relate motions of differing directions. Other researchers have shown that while there are neurons sensitive to translation early in the striate cortex, neurons sensitive to rotation and divergence do not show up until reaching MT and MST. These findings suggest that neural processing of these two types of motion may be similar and consequently would be similar in terms of cognitive demands. The question asked by Thorton and Gilden is what kind of representation is used by attention in acquiring information that specifies direction. The goal is to uncover the type of information that assigns attentional load and this would in turn lead to a better understanding of what is perceived efficiently and why. To determine the level of representation they use two different experimental paradigms. The first is a traditional multiple target search examining spatial parallelism and the second is a signal detection approach. The purpose of the two methodologies is to generalize findings across the late selection models and the early selection models. What they found was that translations and divergence flow produced relatively similar results, that is these two types of optic flow patterns yielded search times and error rates that appeared to be reflective of parallel, capacity limited processing. The curl condition yielded search times that appeared to be consistent with serial processing. In other words, detecting translation flow and divergence flow does not appear to be cognitively demanding or scene-based, while detecting rotation seems to be image-based and requires greater cognitive effort. Local MotionAnother task in motion perception that is relatively effortless under most conditions is tracking an object moving through ones field of view. An object suddenly launched through the air within ones field of view will quickly draw attention. This is particularly he...
