Papers by Marco Bertamini
Behavior Research Methods, 2022
Observers can quickly estimate the quantity of sets of visual elements. Many aspects of this abil... more Observers can quickly estimate the quantity of sets of visual elements. Many aspects of this ability have been studied and the underlying system has been called the Approximate Number Sense (Dehaene, 2011). Specific visual properties, such as size and clustering of the elements, can bias an estimate. For intermediate numerical quantities at low density (above five, but before texturization), human performance is predicted by a model based on the region of influence of elements (occupancy model: Allïk & Tuulmets, 1991). For random 2D configurations we computed ten indices based on graph theory, and we compared them with the occupancy model: independence number, domination, connected components, local clustering coefficient, global clustering coefficient, random walk, eigenvector centrality, maximum clique, total degree of connectivity, and total edge length. We made comparisons across a range of parameters, and we varied the size of the region of influence around each element. The an...
Symmetry, 2022
symmetric patterns are generally preferred to less regular patterns. Here, we studied 2D patterns... more symmetric patterns are generally preferred to less regular patterns. Here, we studied 2D patterns presented as 2D images in the plane, and therefore producing a symmetric pattern on the retina, and the same patterns seen in perspective. This perspective transformation eliminates the presence of perfect symmetry in terms of retinotopic coordinates. Stimuli were abstract patterns of local coplanar elements, or irregular polygons. In both cases they can be understood as 2D patterns on a transparent glass pane. In the first study we found that perspective increased reaction time and errors in a classification task, even when the viewing angle was kept constant over many images. In a second study we tested a large sample (148 participants) and asked for a rating of beauty for the same images. In addition, we used the Cognitive Reflection Test (CRT) to test the hypothesis that people who tend to give the more immediate and intuitive answer would also show a stronger preference for the sym...
Acta Psychologica, 2015
We studied adults' understanding of the relationship between objects and their reflections. Two s... more We studied adults' understanding of the relationship between objects and their reflections. Two studies investigated whether adults performed in a similar way when asked to predict the movement of a reflection in a flat mirror based on the movement of the corresponding object or, vice versa, predict the movement of the material object based on the movement of its reflection. We used simple movements in the experiments: movements in a straight line at various angles with respect to the mirror. Despite the simplicity of the task, some of the participants made incorrect predictions in a percentage of cases ranging from 0% to 54%, depending on the angle. Asymmetries between the two directions of prediction emerged, in particular in terms of types of error. Results confirmed a cognitive difference between deriving the reflected (virtual) world from the "real" (material) world and vice versa. In particular the expectation that something will be opposite in a mirror is more salient when people imagine how a reflection will be with respect to the material world rather than when they imagine how the material world will be with respect to a reflection.
The Editors gratefully acknowledge the assistance of the following persons who acted as referees of contributions to Acta Psychologica in 2004
Reviewers November 2000±October 2001
Exogenous cueing modulates preference formation
Journal of Vision, 2015
Attentional shifts can be produced by external (exogenous) cues. Here we focus on whether a shift... more Attentional shifts can be produced by external (exogenous) cues. Here we focus on whether a shift of attention modulates affective responses. In five experiments, the peripheral onset of an uninformative cue was followed by a novel abstract pattern. We observed that exogenous cuing enhanced target discrimination (RTs) and preference formation (ratings) (Experiment 1a). We therefore distinguish two validity effects: VERTs and VEpreference. Validity effects are measured by the difference between valid and invalid conditions. Interestingly, VEpreference was sensitive to several parameters. When oculomotor responses were inhibited, cuing induced VERTs but not VEpreference (Experiment 1b). Also the cue-to-target (inter-stimulus interval, ISI) interval was critical. By increasing ISI we eliminated both VERTs and VEpreference (Experiment 2a and 2b). Further investigation revealed that the VEpreference originates from a combination of a validity benefit and an invalidity cost (Experiment3). We also investigated whether VEpreference indirectly results from the experience of fluency on valid conditions. The target in Experiment 4 was a simple circle and participants responded to its location. After this response, a non-target pattern appeared at fixation and was evaluated. Although VERTs was present for target detection, VEpreference for non-target patterns at fixation was absent. In Experiment 5 the non-target patterns were presented at the peripheral location of the target. Both VERTs and VEpreference were observed. Preference modulation may thus be determined by a sense of fluency associated with the cue-to-target contingency. However, reorienting attention with an additional saccade can reset the effect. Overall these studies document the relationship between exogenous attention and preference. Our results highlight the important role of attention and oculomotor responses in the mechanism that links visual and emotional responses. Meeting abstract presented at VSS 2015.
Programming Is Fun
Programming Visual Illusions for Everyone
A programming language is a way to give commands to a computer. These commands are written as tex... more A programming language is a way to give commands to a computer. These commands are written as text and when we put many commands together we call that a program. Python® is a high-level, easy-to-read, interpreted language. We will see how to install Python together with an application called PsychoPy (which will be discussed in Chapter 3). We will also see how to write simple commands, perform mathematical operations, and control the flow of the program with if, for and while statements.
Hierarchical Motion Organisation
Programming Visual Illusions for Everyone
This is one of my favourite illusions. It may not be the one that jumps out and is immediately ob... more This is one of my favourite illusions. It may not be the one that jumps out and is immediately obvious, but the implications of this effect are important. Any given motion can be interpreted in different ways based on the frame of reference. We will move a dot on the screen, and depending on the frame of reference it will be seen to move counter-clockwise (relative to the static background) or along a line (relative to its own motion up and down) or clockwise (relative to a bigger system that includes all the dots). In the program we will also learn how to set up some clickable buttons. These will replace the controller and we learn therefore how to do the monitoring of the mouse directly.
i-Perception
We compare two versions of two known phenomena, the Curvature blindness and the Kite mesh illusio... more We compare two versions of two known phenomena, the Curvature blindness and the Kite mesh illusions, to highlight how similar manipulations lead to blindness to curvature and blindness to illusory curvature, respectively. The critical factor is a change in luminance polarity; this factor interferes with the computation of curvature along the contour, for both real and illusory curvature.
A number of studies have explored visual symmetry processing by measuring 16 event related potent... more A number of studies have explored visual symmetry processing by measuring 16 event related potentials and neural oscillatory activity. There is a sustained posterior 17 negativity (SPN) related to the presence of symmetry. There is also functional MRI activity 18 in extrastriate visual areas and in the lateral occipital complex. We summarise the evidence 19 by answering six questions. (1) Is there an automatic and sustained response to symmetry 20 in visual areas? Answer: Yes, and this suggests automatic processing of symmetry. (2) 21 Which brain areas are involved in symmetry perception? Answer: There is an extended 22 network from extrastriate areas to higher areas. (3) Is reflection special? Answer: 23 Reflection is the optimal stimulus for a more general regularity-sensitive network. (4) Is 24 the response to symmetry independent of view angle? Answer: When people classify 25 patterns as symmetrical or random, the response to symmetry is view-invariant. When 26 people attend to ...
How do visual skills relate to action video game performance?
Journal of Vision, 2021
It has been claimed that video gamers possess increased perceptual and cognitive skills compared ... more It has been claimed that video gamers possess increased perceptual and cognitive skills compared to non-video gamers. Here, we examined to which extent gaming performance in CS:GO (Counter-Strike: Global Offensive) correlates with visual performance. We tested 94 players ranging from beginners to experts with a battery of visual paradigms, such as visual acuity and contrast detection. In addition, we assessed performance in specific gaming skills, such as shooting and tracking, and administered personality traits. All measures together explained about 70% of the variance of the players’ rank. In particular, regression models showed that a few visual abilities, such as visual acuity in the periphery and the susceptibility to the Honeycomb illusion, were strongly associated with the players’ rank. Although the causality of the effect remains unknown, our results show that high-rank players perform better in certain visual skills compared to low-rank players.
PeerJ
Background Preference for smooth contours occurs for a variety of visual stimuli. However, there ... more Background Preference for smooth contours occurs for a variety of visual stimuli. However, there are individual differences. Openness to experience, a trait associated with aesthetic appreciation, emotional sensitivity and abstract thinking, correlates with this preference. The evaluation of meaningless stimuli entails automatic associations influenced by knowledge, intellectual interests and individual experiences which are diverse. However, it is difficult to capture this variability in studies restricted to Undergraduate students in Psychology with a prevalence of female participants. Methods Here we examined preference for curvature with 160 undergraduate students in Psychology, Mathematics, Engineering and Computer Science, balanced for gender. Participants viewed abstract shapes varying for contour (angular vs. curved). The shapes presented variations in Vertices (10, 20, 30) and Concavity (30%, 40%, 50%) to increase complexity. Participants rated how much they liked each shap...
Breathing Square Illusion
The Breathing square is an illusion of movement, therefore in this chapter for the first time we ... more The Breathing square is an illusion of movement, therefore in this chapter for the first time we will program an animation. In it, a red square rotates but some parts may be hidden from view. As a consequence the rigid rotation of the square become hard to see and instead the object appears to deform. We will learn how to show an animation on screen, with every image updated every new frame. We set the frame rate to 60 frames per second. This will be done by reading the clock and then waiting without doing anything until the correct amount of time has elapsed (1/60 of a second).
The fact that curved shapes and curved objects are seen as beautiful and attractive has been know... more The fact that curved shapes and curved objects are seen as beautiful and attractive has been known for a long time. Here we discuss the role of curvature with examples from works of art, starting from the earliest paleolithic cave painting and statuines. The strogest theoretical argument for a 'line of beauty' comes from William Hogarth (1759). Recent empirical work has broadly supported the idea that curvature is linked with beauty, although many questions remain about the origin of the effect. An analysis of visual art across the centuries provides support for a curvature preference, but only as one factor that is sometimes absent or sometimes combined with sharp and angular shapes. The aesthetics of smooth contour curvature in historical context
Using a paper-and-pencil task, undergraduate students predicted when a character would be able to... more Using a paper-and-pencil task, undergraduate students predicted when a character would be able to see her reflection in a planar mirror. Experiment 1 showed that participants expected the character to be able to see her reflection earlier than she actually would when moving horizontally, but not when moving vertically, confirming previous findings (Croucher, Bertamini & Hecht, 2002; Bertamini, Hecht, Spooner, 2003), but unlike previous studies the vantage-point from which the character was depicted was identical for both conditions. In Experiment 2 and 3 we tested for the role of body orientation, and relation between the eyes and the mirror surface in explaining these results. We conclude that the early error can be avoided only when the eyes define an axis parallel to the near edge of the mirror. We call this the eye-plane heuristics. Experiment 4 did not reveal a significant increase in the early error with distance from the mirror, and Experiment 5 demonstrated a weak effect of ...
PsychoPy Is Fun
In this chapter we start to use Python within PsychoPy. PsychoPy is an open-source Python tool th... more In this chapter we start to use Python within PsychoPy. PsychoPy is an open-source Python tool that makes it easy to get images and animations on the screen of a computer. It includes a text editor and we will see how to start a program by writing lines and saving the script to a file. In the process of learning how to use PsychoPy we also start learning about objects and object-oriented programming. Once we have created objects we will learn how to draw them on screen and after that we will be ready to write our first program (in Chapter 4).
Perception
Human observers make errors when predicting what is visible in a mirror. This is true for percept... more Human observers make errors when predicting what is visible in a mirror. This is true for perception with real mirrors as well as for reasoning about mirrors shown in diagrams. We created an illustration of a room, a top-down view, with a mirror on a wall and objects (nails) on the opposite wall. The task was to select which nails were visible in the mirror from a given position (viewpoint). To study the importance of the social nature of the viewpoint, we divided the sample ( N = 108) in two groups. One group ( n = 54) were tested with a scene in which there was the image of a person. The other group ( n = 54) were tested with the same scene but with a camera replacing the person. Participants were instructed to think about what would be captured by a camera on a tripod. This manipulation tests the effect of social perspective-taking in reasoning about mirrors. As predicted, performance on the task shows an overestimation of what can be seen in a mirror and a bias to underestimate ...
PLOS ONE
Earlier work by one of us examined a historical corpus of portraits and found that artists often ... more Earlier work by one of us examined a historical corpus of portraits and found that artists often paint the subject such that one eye is centred horizontally. If due to psychological mechanisms constraining artistic composition, this eye-centring bias should be detectable also in portraits by non-professionals. However, this finding has been questioned both on theoretical and empirical grounds. Here we tested eye-centring in a larger (N~= 4000) and more representative set of selfies spontaneously posted on Instagram from six world cities. In contrast with previous selfie results, the distribution of the most-centred eye position peaked almost exactly at the horizontal centre of the image and was statistically different from predictions based on realistic Monte-Carlo predictions. In addition, we observed a small but statistically reliable pseudoneglect effect as well as a preference for centring the left-eye. An eye-centring tendency appears to exist in self-portraits by non-artists.
Scientific Reports
Electrophysiological (EEG) studies of human perception have found that amplitude at posterior ele... more Electrophysiological (EEG) studies of human perception have found that amplitude at posterior electrodes is more negative for symmetrical patterns compared to asymmetrical patterns. This negativity lasts for hundreds of milliseconds and it has been called sustained posterior negativity (SPN). Symmetry activates a network of visual areas, including the lateral occipital complex (LOC). The SPN is a response to presence of symmetry in the image. Given the sustained nature of this activation, in this study we tested the persistence of the SPN after stimulus offset. Two shapes were presented (for 0.5 s each) with a 1 s blank interval in between. We observed a sustained response after stimulus offset, irrespective of whether the task required processing of shape information. This supports the idea that the response to symmetry is generated by information in the image, independently of task, and that it is sustained over approximately one second post stimulus onset. Visual symmetry has an important role in the study of visual perception, and empirical work on perception of symmetry has a long history 1-6. Neurophysiological and neuroimaging work has found evidence, using different methodologies, of tuning to image regularity within ventral, lateral and dorsal occipital cortex, including the Lateral Occipital Complex 7. For example, several ERP studies have shown a regularity-related negativity over parieto-occipital areas (Fig. 1). In this paper, we briefly review this literature, and then present new data about the persistence of the symmetry response after stimulus offset. Observers compared patterns presented in two intervals (500 ms each) separated by a 1000 ms blank interval. This presentation is short compared to that used in previous EEG studies (typically more than 1 s). We use this procedure to (i) analyse persistent activity during the blank interval, and (ii) test whether this persistent activity is present also when shape information is not relevant for the task. In addition, we will analyse the response to the second pattern as a function of its relationship with the first pattern. Observers compared the patterns (symmetrical or asymmetrical) and decided whether they were identical or different. Note that this is a task requiring processing of shape, but not necessarily processing of symmetry. We compared this shape matching task to a different task in which observers were not required to process the shape relationship between patterns (i.e. colour task). It is possible that when participants are engaged in matching the stimuli based on shape information, response to symmetry continues after the first offset; on the contrary when colour is attended, symmetry-related activity might be reduced or absent. To anticipate our results, we report that the activation continues after stimulus offset in both tasks, and this activation does not change (it is not enhanced) when the task requires a comparison and therefore a processing of shape information. With respect to the response to the second stimulus, symmetry-response was enhanced in the second interval when a novel symmetrical exemplar was shown, more than when the same symmetrical pattern was repeated, suggesting a form of symmetry priming. The main focus of the study is the persistence of the response to a visual stimulus after offset, using electroencephalography (EEG) and the analysis of visual evoked potential (VEP). The International Society for Clinical Electrophysiology of Vision (ISCEV) defines three standard VEP protocols based on the type of stimuli used: (a) Pattern-reversal, (b) Pattern onset/offset and (c) Flash 8. For pattern reversal there is no distinction between onset and offset, and the typical VEP has an initial negative deflection (N70), a prominent positive peak (P100), and a later negative component (N155). For pattern onset/offset, the time course is similar but with reversed polarity.
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Papers by Marco Bertamini