fMRI imaging measures brain activity by detecting changes in the brain that are associated with blood flow and can be used in order to determine the size and location of visual field maps. This study measured BOLD responses in humans to understand spatial summation by showing them spatial contrast pattern images through vertical and horizontal apertures.Nonlinear responses can be computed from the visual field responses, from which the spatial summation ratio is calculated. A ratio of less than one indicates a smaller response to exposure to a full aperture or contrast image than predicted by the linear model. Datasets were analyzed using MATLAB, producing eccentricity maps of the visual cortices from stimuli. BOLD response curves identify the intensity of the maps within a particular voxel. The eccentricity maps can then be overlain on anatomical representations of the brain, characterizing the various visual field cortices. Methods of fMRI data analysis are confirmed with the results of this study.

Positive affect, which is known to evoke pleasurable enegagement with one's environment, has well-established potential to reduce the negative effects of stress (Fredrickson, 1998). Although there are various facets of postive affect, we principally examined the alleviating effect of laughter--a common operational defintion of positive affect--on mental and physiological stress responses (Herring et al., 2011). We did so by conducting a replication and extension of a study published by Zander-Schellenberg et al. (2020), who affiirmed the stress-buffering effect of laughter frequency in daily life. In our replication, we attempted to reproduce the findings of the original study, conducted a residual analysis of the statistical models used, and assessed laughter-stress interplay across individual participants. In our extension, we assessed the cumulative stress-buffering effect of laughter frequency in daily life by determining whether the original findings apply to populations of varying daily aggregate laughter frequencies. Our replication results are consistent with the original findings, suggesting that laughter indeed attentuates negative consequences of stress. Interestingly, our extension results only showed this stress-buffering effect at play on days characterized by low daily aggregate laughter frequency. Possible implications of these results are discussed.