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Background: Advanced age is associated with difficulties in understanding the emotional or mental state of others. However, little is known about the underlying cognitive processes that may contribute. We investigate how perspective taking changes in older adults and how this relates to executive and social cognition. Method: Using a novel visual perspective taking (VPT) task, 50 healthy older adults and 122 healthy young adults completed measures of implicit VPT (i.e. egocentric--perspective only) and level one (i.e number of balls seen from egocentric/allocentric) and two (i.e. more balls on left or right from egocentric/allocentric) explicit VPT. Age differences on accuracy and response time (RT) were analysed. Baseline executive and social cognitive functioning were assessed for processing speed, updating, response inhibition, set--switching, affective theory of mind (ToM), and social--emotional cognition. Regression models were used to determine the relationship between VPT, executive, social cognition and ageing. Results: Older adults were slower when required to switch to the allocentric perspective in both level one and two VPT tasks. Congruency effects (impaired performance when scenes were incongruent with the alternate perspective) were identified for accuracy and RT for the egocentric and allocentric conditions of both level one and two explicit VPT. Older adults also displayed a greater congruency effect during the egocentric trials of the level two VPT task. Younger adults displayed a greater congruency effect for errors on the egocentric condition of the level one VPT task. Congruency effect for errors on the allocentric condition of both level one and two VPT tasks correlated with social emotional cognition, such that a greater ability to inhibit the egocentric perspective was associated with better social cognitive performance. Switching to the allocentric perspective was associated with both processing speed and response inhibition and these partially, but not completely, explained the age-related effects on switch cost. A robust implicit VPT effect was identified in both young and older adults. Conclusion: Social difficulties may arise in older adults due to difficulty switching to the allocentric perspective. A greater tendency to rotate into allocentric perspectives during egocentric judgements may reflect a weaker embodied self in older adults. Executive and social cognition are associated with perspective taking ability, but these only partially explain age--related performance differences. Lower level perspective taking difficulty should be considered in studies of social difficulties in advanced age.

Learning associations between words and their referents is crucial for language learning in the developing and adult brain and for language re-learning after neurological injury. Non-invasive transcranial direct current stimulation (tDCS) to the posterior temporo-parietal cortex has been suggested to enhance this process. However, previous studies employed standard tDCS set-ups that induce diffuse current flow in the brain, preventing the attribution of stimulation effects to the target region. This study employed high-definition tDCS (HD-tDCS) that allowed the current flow to be constrained to the temporo-parietal cortex, to clarify its role in novel word learning. In a sham-controlled, double-blind, between-subjects design, 50 healthy adults learned associations between legal non-words and unfamiliar object pictures. Participants were stratified by baseline learning ability on a short version of the learning paradigm and pairwise randomized to active (20 mins; N = 25) or sham (40 seconds; N = 25) HD-tDCS. Accuracy was comparable during the baseline and experimental phases in both HD-tDCS conditions. However, active HD-tDCS resulted in faster retrieval of correct word-picture pairs. Our findings corroborate the critical role of the temporo-parietal cortex in novel word learning, which has implications for current theories of language acquisition.