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The amount of multimedia content shared everyday online recently underwent a dramatic increase. This, combined with the stunning realism of fake images that can be generated with AI-based technologies, undermines the trustworthiness of online information sources. In this work, we tackle the problem of preserving media trustworthiness online from two different points of view. The first one consists in assessing the human ability to spot fake images, focusing in particular on synthetic faces, which are extremely realistic and can represent a severe threat if used to disseminate fake news. A perception study allowed us to prove for the first time how people are more prone to question the reality of authentic pictures rather than the one of last-generation AI-generated images. Secondly, we focused on social media forensics: our goal is to reconstruct the history of an image shared or re-shared online as typically happens nowadays. We propose a new framework that is able to trace the history of an image over multiple sharings. This framework improves the state of the art and has the advantage of being easily extensible with new methods and thus adapt to new datasets and scenarios. In fact, in this environment of fast-paced technological evolution, being able to adapt is fundamental to preserve our trust in what we see.

Yes / This study aimed to develop a clinical test of face perception which is applicable to a wide range of patients and can capture normal variability. The Caledonian face test utilises synthetic faces which combine simplicity with sufficient realism to permit individual identification. Face discrimination thresholds (i.e. minimum difference between faces required for accurate discrimination) were determined in an "odd-one-out" task. The difference between faces was controlled by an adaptive QUEST procedure. A broad range of face discrimination sensitivity was determined from a group (N=52) of young adults (mean 5.75%; SD 1.18; range 3.33-8.84%). The test is fast (3-4min), repeatable (test-re-test r2=0.795) and demonstrates a significant inversion effect. The potential to identify impairments of face discrimination was evaluated by testing LM who reported a lifelong difficulty with face perception. While LM's impairment for two established face tests was close to the criterion for significance (Z-scores of -2.20 and -2.27) for the Caledonian face test, her Z-score was -7.26, implying a more than threefold higher sensitivity. The new face test provides a quantifiable and repeatable assessment of face discrimination ability. The enhanced sensitivity suggests that the Caledonian face test may be capable of detecting more subtle impairments of face perception than available tests. / None

Yes / Faces are highly complex stimuli that contain a host of information. Such complexity poses the following questions: (a) do observers exhibit preferences for specific information? (b) how does sensitivity to individual face parts compare? These questions were addressed by quantifying sensitivity to different face features. Discrimination thresholds were determined for synthetic faces under the following conditions: (i) ‘full face’: all face features visible; (ii) ‘isolated feature’: single feature presented in isolation; (iii) ‘embedded feature’: all features visible, but only one feature modified. Mean threshold elevations for isolated features, relative to full-faces, were 0.84x, 1.08, 2.12, 3.34, 4.07 and 4.47 for head-shape, hairline, nose, mouth, eyes and eyebrows respectively. Hence, when two full faces can be discriminated at threshold, the difference between the eyes is about four times less than what is required when discriminating between isolated eyes. In all cases, sensitivity was higher when features were presented in isolation than when they were embedded within a face context (threshold elevations of 0.94x, 1.74, 2.67, 2.90, 5.94 and 9.94). This reveals a specific pattern of sensitivity to face information. Observers are between two and four times more sensitive to external than internal features. The pattern for internal features (higher sensitivity for the nose, compared to mouth, eyes and eyebrows) is consistent with lower sensitivity for those parts affected by facial dynamics (e.g. facial expressions). That isolated features are easier to discriminate than embedded features supports a holistic face processing mechanism which impedes extraction of information about individual features from full faces.

<p>This study examines the effects of a person's appearence on grading. 80 teachers in Swedish have assessed a text, illustrated with a picture of the supposed author. The pictures were varied by attractiveness, personality in looks, and gender. Furthermore, a text illustrated by a drawing and an unillustrated text were also used in the study. The texts were sent to the teachers by e-mail and assessed on a scale from 1-10 and the Swedish grading scale IG-MVG (Did not pass – Passed – Passed with credit - Passed with great credit). The photos used had been assessed by university students with regards to attractiveness, intelligence, sympatethicness and ambitiousness. The later three categories were put together in a category named Personality in Looks. No significant effects of looks on grading were found in this study. However, substantial differences indicated that attractiveness seems to have a slight negative effect on grading and that the category Personality in Looks seems to have a slightly positive effect. Gender differences were nearly significant, in favour of the male authors.</p>

This study examines the effects of a person's appearence on grading. 80 teachers in Swedish have assessed a text, illustrated with a picture of the supposed author. The pictures were varied by attractiveness, personality in looks, and gender. Furthermore, a text illustrated by a drawing and an unillustrated text were also used in the study. The texts were sent to the teachers by e-mail and assessed on a scale from 1-10 and the Swedish grading scale IG-MVG (Did not pass – Passed – Passed with credit - Passed with great credit). The photos used had been assessed by university students with regards to attractiveness, intelligence, sympatethicness and ambitiousness. The later three categories were put together in a category named Personality in Looks. No significant effects of looks on grading were found in this study. However, substantial differences indicated that attractiveness seems to have a slight negative effect on grading and that the category Personality in Looks seems to have a slightly positive effect. Gender differences were nearly significant, in favour of the male authors.

Title from first page of PDF document. Includes bibliographical references (p. 22-25).

This thesis explores the causes of the face inversion effect, which is a substantial decrement in performance in recognising facial stimuli when they are presented upside down (Yin,1969). I will provide results from both behavioural and electrophysiological (EEG) experiments to aid in the analysis of this effect. Over the course of six chapters I summarise my work during the four years of my PhD, and propose an explanation of the face inversion effect that is based on the general mechanisms for learning that we also share with other animals. In Chapter 1 I describe and discuss some of the main theories of face inversion. Chapter 2 used behavioural and EEG techniques to test one of the most popular explanations of the face inversion effect proposed by Diamond and Carey (1986). They proposed that it is the disruption of the expertise needed to exploit configural information that leads to the inversion effect. The experiments reported in Chapter 2 were published as in the Proceedings of the 34th annual conference of the Cognitive Science Society. In Chapter 3 I explore other potential causes of the inversion effect confirming that not only configural information is involved, but also single feature orientation information plays an important part in the inversion effect. All the experiments included in Chapter 3 are part of a paper accepted for publication in the Quarterly Journal of Experimental Psychology. Chapter 4 of this thesis went on to attempt to answer the question of whether configural information is really necessary to obtain an inversion effect. All the experiments presented in Chapter 4 are part of a manuscript in preparation for submission to the Quarterly Journal of Experimental Psychology. Chapter 5 includes some of the most innovative experiments from my PhD work. In particular it offers some behavioural and electrophysiological evidence that shows that it is possible to apply an associative approach to face inversion. Chapter 5 is a key component of this thesis because on the one hand it explains the face inversion effect using general mechanisms of perceptual learning (MKM model). On the other hand it also shows that there seems to be something extra needed to explain face recognition entirely. All the experiments included in Chapter 5 were reported in a paper submitted to the Journal of Experimental Psychology; Animal Behaviour Processes. Finally in Chapter 6 I summarise the implications that this work will have for explanations of the face inversion effect and some of the general processes involved in face perception.

Call number: LD2668 .T4 1985 S53 / Master of Science-

Master of Science / Department of Psychology / Lester C. Loschky / To investigate the role of various bands of spatial frequencies for drawing, untrained artists drew four portraits from four different bands of spatial frequencies (e.g. unfiltered, 4-8, 8-16, & 16-32 cycles per face width (c/fw)). Raters then judged the accuracy of the drawings in comparison to both the source image from which the drawings were produced and an unfiltered version of the same face. The results show that low spatial frequencies (LSFs) and high spatial frequencies (HSFs) were useful for drawing, relative to middle spatial frequencies (MSFs). Additionally, the unfiltered condition that contained all spatial frequencies produced the most accurate drawings. This suggests that when artists are allowed access to both LSFs and HSFs they are able to utilize the global structure information carried in LSFs as well as the edge and detail information carried in HSFs to create more accurate drawings. The author posits that the MSFs that are useful for face recognition become redundant for drawing and that novice artists discount these MSFs in the control condition in order to increase the saliency and usefulness of the LSFs and HSFs. The results have implications for art education, drawing technology and the development of low-level drawing theory.