Yes / Purpose.: Crowding describes the increased difficulty in identifying a target object when it is surrounded by nearby objects (flankers). A recent study investigated the effect of age on visual crowding and found equivocal results: Although crowded visual acuity was worse in older participants, crowding expressed as a ratio did not change with age. However, the spatial extent of crowding is a better index of crowding effects and remains unknown. In the present study, we used established psychophysical methods to characterize the effect of age on visual crowding (magnitude and extent) in a letter recognition task. Methods.: Letter recognition thresholds were determined for three different flanker separations in 54 adults (aged 18–76 years) with normal vision. Additionally, the spatial extent of crowding was established by measuring spacing thresholds: the flanker-to-target separation required to produce a given reduction in performance. Uncrowded visual acuity, crowded visual acuity, and spacing thresholds were expressed as a function of age, avoiding arbitrary categorization of young and old participants. Results.: Our results showed that uncrowded and crowded visual acuities do not change significantly as a function of age. Furthermore, spacing thresholds did not change with age and approximated Bouma's law (half eccentricity). Conclusions.: These data show that crowding in adults is unaffected by senescence and provide additional evidence for distinct neural mechanisms mediating surround suppression and visual crowding, since the former shows a significant age effect. Finally, our data suggest that the well-documented age-related decline in peripheral reading ability is not due to age-related changes in visual crowding. / Supported by an Age UK Scholarship (AJB); a National Institute of Health Research (NIHR) Postdoctoral Fellowship (ATA); and a Wellcome Trust Career Development Fellowship (BSW).

Contemporary learning theories derive much of their explanatory power from the assumption that all stimuli presented vie for associative strength, the assumption of Shared Weight Space (SWS). Theories based on this assumption have proven successful in explaining many of the observed conditioning phenomena in animals. However, work with humans has proven more complex due to outside knowledge, biases, and heuristics (see, e.g., Chapman, 1991; Msetfi et al., 2005; Perales et al., 2004; Tversky & Kahneman, 1974; Viken et al., 2005; Waldmann, 2000 & 2001). The present series of experiments sought to test the assumption of SWS in a task that is less susceptible to the influence of "top-down" factors. An information processing task (i.e., the correlated flankers task) was used so that human participants were completing a central task (i.e., responding to the target) and were unaware as to the importance of the contingencies in the designs, yet were still exposed to them via the irrelevant information (i.e., flankers). Four compound conditioning phenomena were studied in order to test the assumption of SWS. Evidence for the simple predictions coming from SWS theories was mixed. However, a slightly more complex version of these theories can explain the entire pattern of data quite elegantly.