Manipulating the reliability of target-color information modulates value-driven attentional capture.

Previously rewarded stimuli slow response times (RTs) during visual search, despite being physically non-salient and no longer task-relevant or rewarding. Such value-driven attentional capture (VDAC) has been measured in a training-test paradigm. In the training phase, the search target is rendered in one of two colors (one predicting high reward and the other low reward). In this study, we modified this traditional training phase to include pre-cues that signaled reliable or unreliable information about the trial-to-trial color of the training phase search target. Reliable pre-cues indicated the upcoming target color with certainty, whereas unreliable pre-cues indicated the target was equally likely to be one of two distinct colors. Thus reliable and unreliable pre-cues provided certain and uncertain information, respectively, about the magnitude of the upcoming reward. We then tested for VDAC in a traditional test phase. We found that unreliably pre-cued distractors slowed RTs and drew more initial eye movements during search for the test-phase target, relative to reliably pre-cued distractors, thus providing novel evidence for an influence of information reliability on attentional capture. That said, our experimental manipulation also eliminated value-dependency (i.e., slowed RTs when a high-reward-predicting distractor was present relative to a low-reward-predicting distractor) for both kinds of distractors. Taken together, these results suggest that target-color uncertainty, rather than reward magnitude, played a critical role in modulating the allocation of value-driven attention in this study.

Perceptual Fading of a Stabilized Cortical Image: Replication in the Undergraduate Classroom.

Prolonged exposure to a stimulus causes desensitization of cortical neurons and results in perceptual changes. One example of this phenomenon is contrast adaptation, in which perceived differences between light and dark regions of a stimulus decrease. Blakemore, Muncey, and Ridley reported evidence for the "perceptual fading of a stabilized cortical image" in a 1971 Nature paper. Our goal was to replicate their second experiment, in which adaptation was measured across many contrasts, and develop an active learning exercise for undergraduate students. The experiment was coded using an open-source python package and psychophysical data were collected from two observers. On each trial, a sinusoidally modulated luminance grating appeared above fixation, and the task of the observer was to adjust the contrast of a grating below fixation until the two appeared identical. Between trials in the adaptation condition, a high contrast grating was presented in the top location; no such grating appeared between trials in the control condition. Contrast matches showed a clear reduction during the adaptation condition, thus demonstrating perceptual fading and a successful replication of Blakemore et al. (1971) We then simplified the approach and modified the code to create a single, seamless experience for use in the classroom. With instructions and theoretical background provided in a one-page handout, students can perform the experiment on themselves and view their results in an automatically generated figure. This exercise, a primary example of active learning, will help students gain a first-hand understanding of the perceptual effects of adaptation.