Hick/Hyman Law:  One of the earliest and most-striking results in the study of human information processing is the near-perfect, linear relationship between uncertainty (as defined under Communication Theory) and mean response time.  Our recent work in this area has concerned the seperate effects of stimulus and response uncertainty, as well as residual differences in mean response time between the sub-conditions that are used to set the level of (overall) uncertainty.  Learn More

Redundancy Gains:  When people are given more than one reason to make a response, they usually make the response more quickly.  This phenomenon is known as a redundancy gain  because any additional reasons are redundant with the first but they still produce a gain in performance.  The primary questions in the study of redundancy gains are Why do they occur? and At what level within the system do they occur?  These are questions that we have addressed in the past and continue to study.  Learn More

Contingency Effects​:  If one stimulus or event is a reliable predictor of some other stimulus or event, a contingency exists between them and most creatures -- including people -- will "pick up" and learn the association.  Early in our work (starting with redundancy gains; see above), we viewed this as an issue that researchers ought to avoid, as these contingencies can act as confounds, causing errors in conclusion.  More recently, we have explored the similarities between these effects and other types of Hebbian learning, and we have used these effects as a tool to address other cognitive questions.

Lateralized Readiness Potential:  Prior to the production of a voluntary movement by the left or right arm, an asymmetry in voltage can be detected over the pre-central gyri using scalp elctrodes; this is the Lateralized Readiness Potential  (LRP).  Like many other event-related brain potentials, the LRP is a useful "time marker" -- in this case, for the onset of response-specific processing.  By examining whether a given effect on performance (e.g., the response-time advantage for multiple targets) also influences the timing of the LRP, one can determine whether the effect occurs prior to the motor system.  Note, however, that detecting the onset of the LRP is complicated, which is why we have also conducted large-scale simulations to determine which method works best.

Exogenous Spatial Cuing:  Any salient visual event can "capture" visual attention.  This usually causes an advantage in processing at the location of the salient event for at least a brief period.  Under some conditions, however, the same salient event that causes an advantage in processing when there are only a few possible locations can cause a large disadvantage when there are many locations.  After first documenting this finding, we went on to explain it.  In brief: the disadvantage with many locations is caused by several factors, including the large proportion of trials on which the salient event and the target appear at different locations, plus a benefit due to apparent motion on these same trials.

Simon Effects:  In a task requiring left vs right responses to a non-spatial attribute of a stimulus (such as its color), the location at which the target is presented has a large effect on performance -- responses are both faster and more accurate when the target is presented on the same side of the midline as the correct button to press.  This is the Simon Effect  (named for J. Richard Simon of the University of Iowa, discoverer of the effect).  Our work has centered on two questions: what perceptual codes [plural!] are responsible for the effect and why does the size of the effect depend on recent events.