According to the Socioemotional Selectivity Theory (SST), the normal aging process is associated with a greater emphasis on self-regulation of emotional states, and this fosters a bias in cognitive processing for information that is positively valenced (e.g., pleasant images and autobiographical events, happy faces), such that older adults have better memory for, and pay greater attention to, positive relative to negative valenced information (a ???positivity effect???). Two hypotheses have recently emerged which differ in the cognitive mechanism proposed to account for the emergence of aging-related positivity effects. The first, termed the ???cognitive control??? hypothesis, suggests that positivity effects arise from older adults' directed application of cognitive efforts to preferentially process positive information, essentially a top-down explanation. The second is a bottom-up hypothesis, suggesting that positive information is relatively easier (more fluent) for older adults to detect and process, compared to negative information, due to changes in amygdala reactivity to negative stimuli, and is termed the "processing fluency" hypothesis. To evaluate these hypotheses, I conducted a suite of memory and attention experiments and compared performance of younger and older adults. I used five different tasks (three different memory tasks, and two different attention tasks) which varied with respect to the degree to which each allowed for the use of cognitive control, and was reflective in nature, or emphasized fluency (i.e., speed of processing and output). In Experiments 1 and 2, I examined the effect of age on two different types of memory task that differed with respect to the degree to which participants must rely on cognitive control/reflective processing or processing fluency to successfully complete the task. Clear positivity effects were found on the task that was reflective in nature (autobiographical memory task) but not on the task that relied more heavily on fluency (phonemic fluency task). In Experiment 3, I examined whether older adults strategically select positive information to later remember (i.e., use cognitive control to regulate encoding of positive material), by asking participants to judge the likelihood of remembering positive, negative, and neutral pictures for a later memory test. In line with a strategic bias, older, but not younger, adults showed a positivity effect in terms of the number of pictures selected as particularly memorable, though both age groups showed a positivity effect in picture recall. Within the domain of attention-based tasks, in Experiments 4a and 4b I used a Rapid Serial Visual Presentation (RSVP) paradigm to examine whether older adults were more likely to detect (or have attention captured by) rapidly presented positive, than negative or neutral, pictures compared to younger adults. Given the rapid rate of presentation in this paradigm, it is unlikely that participants would be able to use cognitive control to strategically direct attention to positive stimuli, thus performance was taken to measure fluency-mediated biases for the pictures of different valence. Results showed little evidence for a positivity effect. In Experiments 5a and 5b, again within the domain of attention, I examined whether older adults preferentially oriented attention toward positive, and/or away from negative, relative to neutral stimuli, on a dot probe task in which trial timings were long enough to allow for strategic control. Experiment 5a used faces whereas Experiment 5b used pictures as stimuli, in an effort to determine whether findings could generalize across different types of stimuli. Some evidence of positivity effects were found, as older adults were less biased to attend to negative (angry) faces compared to younger adults. Results across this series of experiments are consistent with the hypothesis that positivity effects in older adults' memory and attention stem from the strategic application of effortful, reflective, cognitive processing, rather than a bottom-up difference in processing fluency.

Socioemotional selectivity theory posits that as people age, they become motivated and successful at maximizing positive emotions and minimizing negative ones. Yet, 70% of older adults report physical pain, which is associated with negative affect. The strategies and resources that older adults use to maintain positive affect in the face of pain remain largely unknown. Specific positivity-enhancing strategies include recalling, recognizing, and responding to positive stimuli and prioritizing close over knowledgeable social partners. Executive functions (EF, i.e., task-switching, working memory, and inhibition) and heart rate variability (HRV) may be important resources for coping with pain. The current project used two studies to test whether older adults used positivityenhancing strategies and maintained emotional wellbeing following pain more than younger adults; associations with EF and HRV were also investigated. In Study 1, 50 older and 50 younger adults experienced a control and a pain condition, were given the chance to employ positivity-enhancing strategies, and provided EF and HRV data. Study 2 used longitudinal data from community-dwelling older adults (n =150) to test whether task-switching moderated the within-person relationship between pain and wellbeing. In Study 1, after the pain condition, younger adults demonstrated lesser preference toward knowledgeable social partners than older adults (γ = -0.15, p = .016). No other age group x pain condition x valence interactions were found. Older and younger adults did not differ in changes in positive or negative affect following pain. Task-switching and HRV were both associated with reduced preference for knowledgeable social partners following pain, but no other significant EF or HRV interactions were found. Study 2 failed to support the hypothesis that task-switching protected against pain-related declines in wellbeing. Future research on strategies that older adults use to maintain emotional wellbeing in the face of pain is needed.

Dans le vieillissement « sain », la préférence pour les stimuli positifs augmente par rapport aux stimuli négatifs. Ce phénomène est appelé « effet de positivité » et peut être observé au niveau comportemental et cérébral. L'objectif principal de cette thèse a été de caractériser les effets de l'âge sur les traitements émotionnels afin d'améliorer notre compréhension des effets de positivité. L'objectif sous-jacent a été d'évaluer dans quelles conditions ces effets peuvent conduire à une plus grande vulnérabilité des personnes âgées face à des situations menaçantes. Une première étude en électroencéphalographie a révélé que l'engagement attentionnel pour des scènes naturelles négatives diminue avec l'âge quel que soit leur niveau d'activation dans une tâche de catégorisation affective. A l'inverse, ce dernier reste inchangé pour les situations positives, conduisant à une réduction des biais de négativité. Une deuxième étude en électroencéphalographie, dont le paradigme était similaire à la première étude, a mis en évidence que les biais de négativité restent préservés avec l'âge lorsque l'évaluation des scènes s'effectue sur la dimension de « tendance à l'action ». Une troisième étude révèle que l'attention volontaire sur les situations d'intérêt des personnes âgées (positives) et sur les processus d'évaluation modulés par l'âge est nécessaire à l'émergence des effets de positivité. Parallèlement à ces travaux, une méthodologie innovante est proposée pour la classification d'états émotionnels des personnes jeunes et âgées sur la base de leurs signaux électroencéphalographiques. Nous avons obtenu des résultats encourageants qui suggèrent la possibilité cette méthode pour implémenter des interfaces cerveau-machine pour protéger les personnes âgées d'une éventuelle vulnérabilité en raison des effets de positivité. L'ensemble de ces travaux suggèrent que les effets de positivité sont les conséquences de changements sur le plan motivationnel de l'individu âgé, touchant principalement les processus d'évaluation émotionnel. La personne âgée régulerait ses émotions et diminuerait l'impact des émotions négatives lorsque d'autres motivations plus prioritaires sont absentes. / With aging, the preference for positive stimuli increases compared to negative stimuli. This is called “positivity effect” and it may be observed in both behavior and brain activity. The main goal of this work was to characterized age effects on emotional processing to improve our understood of this positivity effect. The second goal was to evaluate in which conditions these effects could make older people more vulnerable when they are confronted to threatening situations. A first EEG study revealed that the attentional engagement decreased with age for negative stimuli, regardless of their activation level, in an affective categorization task. Conversely, the processing of positive stimuli was preserved with age and, consequently, a reduction of the negativity bias was observed. In a second EEG study, using a similar paradigm to study 1 with the exception of the task which was an “action tendency task”, we observed a preservation of the negativity bias. A third study revealed that the voluntary attention on interest situations for aged adults (positive) and on appraisal process modulated with age was requisite to observe positivity effects. Parallel to this work, a new method was proposed to recognize and classify emotional states based on EEG signals. We obtained encouraging results which suggest the possibility to use this method to elaborate brain-computer interfaces to protect old people against a potential vulnerability due to positivity effect. Taken together, these results demonstrate that positivity effect is due to motivational shifts with age. Older people would be motivated to increase their well-being and would regulate their emotions by reducing the impact of negative stimuli, provided no other more important motivations are absent.

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