Il mio triangolo

Il triangolo di Kanizsa è divenuto, a partire dalla sua apparizione nella letteratura scientifica nel 1954, un’autentica icona, utilizzata per veicolare l’idea che la percezione visiva è, almeno in parte, un’attività creativa, in grado di sorprendere l’osservatore e di farlo riflettere sul rapporto tra apparenza e realtà. Poche altre immagini prodotte dalla ricerca in psicologia sperimentale hanno conosciuto analoga popolarità e sono state così diffusamente reimpiegate nella comunicazione visiva. Questa "Lezione Magistrale" riunisce, per la prima volta, la genesi del fenomeno e l’evoluzione della sua interpretazione teorica, sviluppatasi nell’arco di un trentennio

CAPTCHaStar! A novel CAPTCHA based on interactive shape discovery

Over the last years, most websites on which users can register (e.g., email providers and social networks) adopted CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) as a countermeasure against automated attacks. The battle of wits between designers and attackers of CAPTCHAs led to current ones being annoying and hard to solve for users, while still being vulnerable to automated attacks. In this paper, we propose CAPTCHaStar, a new image-based CAPTCHA that relies on user interaction. This novel CAPTCHA leverages the innate human ability to recognize shapes in a confused environment. We assess the effectiveness of our proposal for the two key aspects for CAPTCHAs, i.e., usability, and resiliency to automated attacks. In particular, we evaluated the usability, carrying out a thorough user study, and we tested the resiliency of our proposal against several types of automated attacks: traditional ones; designed ad-hoc for our proposal; and based on machine learning. Compared to the state of the art, our proposal is more user friendly (e.g., only some 35% of the users prefer current solutions, such as text-based CAPTCHAs) and more resilient to automated attacks.Comment: 15 page

Lo sguardo degli studenti sulle ingiustizie a scuola

Students’ perceptions regarding injustice at school are widespread in every educational stages and refer especially to classroom management and learning assessment strategies used by teachers. In this contribution we present the results of an investigation about injustice at school, realized asking to 175 university students of three different courses (Primary education sciences and Human Resource Development at University of Milan – Bicocca and Engineering Management of Politecnico di Milano) to describe one incident of injusticeregarding their past school experiences. The research was conducted using mixed method approach. The results highlight the importance of student’s perception of injustice about the relationship between students and teachers and among students, the importance of assessment criteria and the importance of teaching strategies adopted.I vissuti di ingiustizia sono molto diffusi tra gli studenti di qualsiasi ordine di scuola ed essi si riferiscono soprattutto alla gestione della classe da parte degli insegnanti e alla valutazione degli apprendimenti. In questo articolo vengono riportati i primi risultati di un’indagine condotta chiedendo a 175 studenti universitari di Scienze della Formazione Primaria, Formazione e Sviluppo delle Risorse Umane (Università di Milano Bicocca) e di Ingegneria Gestionale (Politecnico di Milano) di descrivere un episodio di ingiustizia di cui erano stati soggetti o testimoni a scuola. L’analisi, condotta con metodi qualitativi e quantitativi, secondo l’approccio mixed-method, ha fornito interessanti riflessioni sul peso che i vissuti di ingiustizia degli studenti hanno nella relazione in classe con gli insegnanti e con i compagni, nella valutazione e più in generale nel processo di insegnamento e apprendimento

Giustizia e ingiustizia a scuola nelle parole dei futuri maestri

The words justice and injustice often feature in students’ reflections on their experience of school, most frequently in relation to assessment, teacher-student relations and modes of class management.In this paper, we present the preliminary results of a study in which 82 trainee primary school teachers described both an episode of justice and an episode of injustice that they had either directly experienced or witnessed during their own school years. The data analysis was carried out using mixed-mode methodology and provided interesting insights into issues such as assessment and relationships in the classroom, as well as highlighting the need for teachers to receive training in interpersonal skills to complement their subject knowledge.Le parole giustizia e ingiustizia ricorrono spesso nelle riflessioni che gli studenti fanno sulla loro esperienza scolastica e coinvolgono la valutazione scolastica, la relazione insegnante-allievi e in generale le modalità con cui è gestita la classe. In questo articolo vengono riportati i primi risultati di un’indagine condotta chiedendo a 82 studenti universitari di Scienze della Formazione Primaria di descrivere un episodio di giustizia e uno di ingiustizia di cui erano stati soggetti o testimoni a scuola. L’analisi, condotta con metodi qualitativi e quantitativi secondo il paradigma del mixed-method, ha fornito interessanti riflessioni sul tema della valutazione e della relazione in classe oltre a suggerire indicazioni per una formazione degli insegnanti che ai contenuti disciplinari affianchi buone capacità relazionali

Perceptual grouping ability in Williams syndrome: Evidence for deviant patterns of performance

Williams syndrome (WS) is a rare genetic disorder. At a cognitive level, this population display poor visuo-spatial cognition when compared to verbal ability. Within the visuo-spatial domain, it is now accepted that individuals with WS are able to perceive both local and global aspects of an image, albeit at a low level. The present study examines the manner in which local elements are grouped into a global whole in WS. Fifteen individuals with WS and 15 typically developing controls, matched for non-verbal ability, were presented with a matrix of local elements and asked whether these elements were perceptually grouped horizontally or vertically. The WS group were at the same level as the control group when grouping by luminance, closure, and alignment. However, their ability to group by shape, orientation and proximity was significantly poorer than controls. This unusual profile of grouping abilities in WS suggests that these individuals do not form a global percept in a typical manner

The occlusion illusion: partial modal completion or apparent distance?

In the occlusion illusion, the visible portion of a partly occluded object (eg a semicircle partly hidden behind a rectangle) appears to be significantly larger than a physically identical region that is fully visible. This illusion may occur either because the visual system 'fills in' a thin strip along the occluded border (the partial-modal-completion hypothesis) or because the partly occluded object is perceived as farther away (the apparent-distance hypothesis). We measured the magnitude of the occlusion illusion psychophysically in several experiments to investigate its causes. The results of experiments 1-3 are consistent with the general proposal that the magnitude of the illusion varies with the strength of the evidence for occlusion, supporting the inference that it is due to occlusion. Experiment 4 provides a critical test between apparent-distance and partial-modal-completion explanations by determining whether the increase in apparent size of the occluded region results from a change in its perceived shape (due to the modal extension of the occluded shape along the occluding edge, as predicted by the partial-modal-completion hypothesis) or from a change in its perceived overall size (as predicted by the apparent-distance hypothesis). The results more strongly support the partial-modal-completion hypothesis

Judging distance across texture discontinuities

Sinai et al (1998 Nature 395 497 - 500) showed that less distance is perceived along a ground surface that spans two differently textured regions than along a surface that is uniformly textured. We examined the effect of texture continuity on judged distance using computer-generated displays of simulated surfaces in five experiments. Discontinuities were produced by using different textures, the same texture reversed in contrast, or the same texture shifted horizontally. The simulated surface was either a ground plane or a frontoparallel plane. For all textures and both orientations, less distance was judged in the discontinuous conditions than in continuous conditions. We propose that when a surface contains a texture discontinuity, a small area adjacent to the perceived boundary is excluded from judged distances

The phantom illusion

It is well known that visible luminance gradients may generate contrast effects. In this work we present a new paradoxical illusion in which the luminance range of gradual transitions has been reduced to make them invisible. By adopting the phenomenological method proposed by Kanizsa, we have found that unnoticeable luminance gradients still generate contrast effects. But, most interestingly, we have found that when their width is narrowed, rather than generating contrast effects on the surrounded surfaces, they generate an assimilation effect. Both high- and low-level interpretations of this “phantom” illusion are critically evaluated