Cool (we think) Ongoing Research
The "Width" of Attention During Search
A curious, but often replicated (e.g., Hout & Goldinger, 2010), finding in visual search is that observers have better incidental memory for distractors when the search task is relatively challenging (e.g., when they're looking for a poorly specified target, or searching for multiple targets at one time). One explanation for this is that, when search templates are poorly specified, there is a greater likelihood for distractors to share a feature with the template, and capture attention. Another explanation is that observers simply allocate more attentional resources to the search display when they know that the task is challenging. Juan Guevara Pinto and I tested these hypotheses across several RSVP search tasks during which peripheral distractors occasionally appeared at various eccentricities off center. If challenging search involves greater search stream attention, observers should be more likely to miss peripheral distractors, right? That's exactly what we found! We also found that search performance was correlated with incidental distractor recognition, further confirming that observers do well because of enhanced search stream attention. Juan presented these results at VSS this year.
Unfamiliar Face Matching has Amnesia
Although people are often described as face perception and recognition experts, this expertise is really only extended to people with whom we are personally familiar. Whereas friends and family members can be recognized across decades, despite myriad changes in their appearance, individuals with whom we are unfamiliar are challenging to recognize, especially after substantial periods of time. Laura Heisick and I recently finished a series of four experiments investigating what people remember about individuals encountered within an unfamiliar face matching task. For example, if you go through airport security, will the TSA agent remember having seen you? Our research suggests that the answer to this question is "no." Although we presented observers in our study with identical images across "study" and test, which confounds person and picture recognition, performance was still barely above chance! We are currently revising the manuscript for resubmission.
The LPE Transfers across Visual Tasks
Juan Guevara Pinto and I presented the results of several studies on the transfer abilities of the low-prevalence effect in visual search at Psychonomics last year (in fact, Juan won a travel award from the Psychonomic Society for it!). During visual search, observers learned the relative prevalence of two targets (or two categories of targets), inducing an LPE in some of our observers. Later, they completed a series of change-detection trials in which the high- or low-prevalence targets could appear. Observers who were sensitive to the LPE during visual search were also impaired during the change detection trials (with the low-prevalence target). This occurred even when the change detection target was only categorically related to the search target! We can't really express how cool we think this is, and are conducting a series of follow-up investigations with Stephen Walenchok from ASU.
Neural Sharpening in Continuous Recognition Memory
Neurocomputational models often posit the existence of sparse, distributed coding in the human hippocampus (and we have found evidence for this in the past! See left). A related proposal is the existence of neural sharpening mechanisms, by which cells involved in coding a memory inhibit surrounding cells (e.g., lateral inhibition) when their preferred stimulus is present. We have recently finished a project in which we find evidence for this neural sharpening at the single-unit level (Wixted et al, 2018), and are currently exploring follow-up projects using spoken words. In the spoken words projects, listeners hear words spoken in multiple voices, allowing us to further explore the single-unit representation of memory, but with greater precision. Although most studies explore the impact of stimulus-driven activity, we're finding evidence for cool effects much earlier -- during the pre-stimulus baseline! (And no, we're not going to appeal to psychic abilities or something.) A presentation is currently in the works for the Society for Neuroscience meeting..
Developing Expertise in Visual Search
We're revising a manuscript for Attention, Perception, and Psychophysics describing the cognitive and oculomotor changes that occur as visual search expertise develops. Participants simultaneously searched displays for 20 target categories, with some targets appearing more frequently than others, over a series of repeated hour-long sessions. Because each display contained between 0 and 3 targets, we were able to measure participants' eye movements as they decided to stop searching (e.g., after finding all targets or deciding that the display contained none), as well as how efficiently they scanned each display. As experience developed, targets were located more quickly, distractors were more likely to be avoided (see right), and, if participants looked at a distractor, they "rejected" it more quickly. Overall, results show that eye movement variables (e.g., saccade velocity, amplitude) improve with experience, and that mental representations become better refined over time. More interestingly, we also show how the development of expertise affects the "shape" of observers functional viewing fields! This project is a collaboration between us and researchers at NMSU (led by Michael Hout).