Carolina Sáez Linero, researcher at the CAS research group, defended her PhD thesis titled “Personalised advertising in the algorithmic logic of platforms. Exploring bias, vulnerability and social inequality”, supervised by Dr Mònika Jiménez-Morales and Dr Isabel Rodríguez-de Dios. The defence took place on Friday, 12 December 2025 at 10:00 a.m.

The research analyses the role of personalised advertising within the algorithmic logic of digital platforms and its contribution to the reproduction of social inequalities. From a critical perspective, the thesis examines how advertising segmentation and algorithmic distribution can introduce dynamics of exclusion, biases in content interpretation, and new forms of socio-economic vulnerability. The study pays particular attention to the experience of young people, exploring their perception of personalised advertising, their objective and subjective knowledge of these systems, the strategies they develop to cope with them, and the way in which the power attributed to algorithms can reinforce the authority of personalised content and its capacity to influence.

From a methodological perspective, the thesis adopts a mixed design that combines an exploratory approach with a quantitative approach. In a first phase, a systematic literature review and a theoretical analysis were conducted using databases such as Web of Science and Scopus, as well as grey literature and empirical and theoretical studies. In a second quantitative phase, the study includes an online survey of 1,200 young people aged between 14 and 30 residing in Catalonia, using validated and adapted scales and real TikTok and Instagram videos as stimuli. The methodology is complemented by an experiment conducted with 300 young people aged between 18 and 25 in the United States, TikTok users, which includes pretests and exposure to two visual stimuli.

Overall, the thesis offers a holistic view that combines theoretical analysis, empirical evidence, and experimentation, and highlights that personalised advertising is not neutral, but rather tends to reinforce structural inequalities and generate new forms of vulnerability. The research shows that historical advertising segmentation logics already produced unequal exposure, and that the incorporation of algorithmic systems increases discriminatory potential by relying on dynamics of profiling, opacity, and surveillance. It also shows that, although young people recognise personalisation and express concern about privacy, they rarely take protective actions, in a context in which platform design normalises personalisation and limits users’ sense of agency. Finally, the thesis indicates that personalised advertising reproduces class and gender biases, reinforces vulnerabilities, and influences self-perception and the willingness to interact with advertising content.

The examination committee, composed of Dr Beatriz Feijoo-Fernández (chair), Dr Ana Jorge (member), and Dr Lluis Mas-Manchón (secretary), highlighted the strength and relevance of the results and offered suggestions for future lines of research. The candidate received the grade of cum laude.

 From left to right: Dr Ana Jorge, Dr Isabel Rodríguez-de Dios, PhD candidate Carolina Sáez-Linero, Dr Mònika Jiménez-Morales, Dr Beatriz Feijoo-Fernández, and Dr Lluís Mas-Manchón.