1,721,254 research outputs found
Statistical validity of the results obtained in small sample size experiments. A parametric test simulation [Validità statistica dei risultati in esperimenti a bassa numerosità campionaria. Simulazione di un test parametrico]
No full textMany authors have criticized small sample size experiments because of the lack of statistical reliability, on the basis of the statistical power and considering a subjective evaluation of prior probability of the null Hypothesis H0 (Cohen, 1994; Chertow, Palevsky e Green, 2006). The aim of the present study is to test the reliability of significant results obtained from the small sample size experiments in comparison with larger ones. The different samples (10, 20, 40, 80, 160) are obtained by monte Carlo simulation, representing two conditions: H0 true and H0 false. As parametric procedure, the linear regression analysis has been used. Thus, the frequency of the type i error and the false positive rate probability (FPRP) have been evaluated. The frequency of the i type error is around 5%, independently on the sample size. Moreover, the FPRP values obtained in the small size samples are comparable to the values obtained in the larger samples. In conclusion the significant results obtained in small size samples are reliable and have statistical validity as well as those obtained in larger samples. This is true even from a Bayesian point of view when a non-informative a priori probability of H0 is taken
Percorsi di ricerca-azione. Lo screening dei prerequisiti
No full textLe difficoltà di apprendimento nella popolazione in età scolare sono stimate tra il 7 e il 10% e rappresentano un alto rischio per il successo scolastico, per il futuro adattamento sociale e per lo sviluppo della personalità. La legge 170/2010 sui Disturbi Specifici di Apprendimento (DSA), il MIUR e il Ministero della Salute sottolineano l’importanza di un’osservazione sistematica dei prerequisiti della lettura, della scrittura e del calcolo. Già nell’ultimo anno della scuola dell’infanzia è possibile infatti rilevare indicatori predittivi di successive difficoltà e mettere in atto percorsi di potenziamento che possano ridurre in misura sostanziale le ricadute negative sulle capacità di apprendimento del linguaggio scritto, non solo nei bambini con DSA ma in tutti quelli con Bisogni Educativi Speciali.
Nato dall’esperienza di clinici e insegnanti, questo volume fornisce indicazioni e materiali sia per valutare in modo semplice e rapido i principali indicatori dello sviluppo delle competenze scolastiche, sia per elaborare specifici piani di intervento. Tramite le Risorse online mette inoltre a disposizione uno strumento per stampare i protocolli di osservazione, compilare le griglie di rilevazione dati e definire automaticamente i profili individuali e collettivi, nonché la tipologia degli interventi necessari, semplificando il lavoro di insegnanti e altri professionisti
Information theory, machine learning, and Bayesian networks in the analysis of dichotomous and Likert responses for questionnaire psychometric validation
Full text linkQuestionnaire validation is indispensable in psychology and medicine and is essential for understanding differences across diverse populations in the measured construct. While traditional latent factor models have long dominated psychometric validation, recent advancements have introduced alternative methodologies, such as the "network framework." This study presents a pioneering approach integrating information theory, machine learning (ML), and Bayesian networks (BNs) into questionnaire validation. Our proposed framework considers psychological constructs as complex, causally interacting systems, bridging theories, and empirical hypotheses. We emphasize the crucial link between questionnaire items and theoretical frameworks, validated through the known-groups method for effective differentiation of clinical and nonclinical groups. Information theory measures such as Jensen-Shannon divergence distance and ML for item selection enhance discriminative power while contextually reducing respondent burden. BNs are employed to uncover conditional dependences between items, illuminating the intricate systems underlying psychological constructs. Through this integrated framework encompassing item selection, theory formulation, and construct validation stages, we empirically validate our method on two simulated data sets-one with dichotomous and the other with Likert-scale data-and a real data set. Our approach demonstrates effectiveness in standard questionnaire research and validation practices, providing insights into criterion validity, content validity, and construct validity of the instrument
Coherent motion and coherent form perception in developmental dyslexia
No full textThe role of visual perception in Developmental Dyslexia (DD) is still controversial. Although the Magnocellular theory of DD has been widely criticized, it is still unclear if the deficit in motion perception is specific for the Magnocellular system or if it is connected to a general difficulty in discriminating signal to noise.
The aim of this study is to investigate dorsal and ventral pathways in different conditions of noise in a population of DD. Seventeen DD and forty-three typically developed (TD) children (age 7-12 years) participated in the study. All the subjects performed the Motion coherence test and the Form coherence test. In the motion coherence test the ability in discriminating the direction of luminance coherent moving dots in different levels of noise is reported. The Form test measures the ability in form recognition in different condition of noise.
The MANOVA showed that DD differed from TD both in the Motion and in the Form coherence tests. Moreover, these differences are significant only in intermediate noise conditions.
These results are in accordance with the noise exclusion theory of DD and added important information about the DD deficit in discriminating signal to noise
Visual search during motion perception
No full textEye movements during motion tracking or smooth pursuit have been widely investigated. However, it is still unclear how eye movements and motion perception system are related. We aim to analyze the pattern of gaze during coherent motion perception in absence of tracking at the very early stage of the motion perception process. Moreover, we would measure if good performances in motion perception are guided by specific gaze pattern. We measured the gaze in twenty-five healthy subjects using eye tracker system (SMI500) during motion perception tasks (coherent motion test), and during visual search of static elements (i.e. searching coloured dots within a group of white dots). The subjects are divided in two groups: good motion perception performers (scoring above the 50% of the total trials) and bad motion performers. The gaze is analyzed by means of specific parameters obtained from the eye movements recordings: the length of the eye movement track plotted on a bidimensional plane, the area of the confidence ellipse of the eye position, the standardized length (obtained by the ratio between the length and the area of the confidence ellipse), the flattening and the slope of the confidence ellipse. Significant differences in gaze patterns are found between motion perception and static visual search tasks. The gaze during motion perception is characterized by stronger flattening of confidence ellipse and longer length of eye movement track. The good performers have significantly longer length and standardized length of the eye movements track as compared to bad performers. These results show that the motion detection requires longer gaze path with respect to static visual search and that the path length is longer in good than in bad performers. In conclusion, the efficiency in motion detection is related to longer length of the gaze path (i.e. mean velocity) more than to the area scanned by the different gaze positions
Typical development of Motion perception and Form discrimination abilities in children
No full textVisual functions have been widely investigated in patients with developmental
disorders. This study aims to analyze the development of dorsal
and ventral visual function in children with typical development, measured
as motion and form discrimination abilities. A sample of 304 children
(age: 4-12 years; 154 males) participated in the experiment. Non-verbal
intelligence (Raven’s matrices), visual acuity (Lea test), motion perception
(motion coherence test-MCT) and form recognition (form coherence
test-FCT) were assessed. The MCT consists of 150 white dots on a black
background moving coherently at a constant velocity in one of the eight
directions (signal) or in a Brownian manner (noise). The task was to recognize
the direction of the signal dots. The FCT consists of white dots (signal)
composing one of eight possible forms through spatial alignment of the
dots, the noise was created by non-aligned dots distorting the form. The
task was to recognize the form. Difficulty was increased by reducing the
dot coherence (signal/noise) from 100% (no noise) to 36% in five levels.
MANOVA showed a significant increment of motion and form perception
accuracy with age, steeper for form as compared to motion recognition.
Both functions are influenced by noise but motion discrimination seemed
to be less affected. While noise had a stronger effect on the younger children
in the FCT (worse performance with noise in the youngest) no such
age effect was found in MCT. Motion and form perception are related
to general intelligence at different ages as well as to the visual acuity.
These results confirm the slowness in development of dorsal function
as compared to ventral function. Visuo-spatial attention, general intelligence
and visual acuity mediate the visual functionality development
L'effetto Simon: il suo decorso temporale con stimoli visivi e risposte oculo-motorie
No full textL’effetto Simon consiste in una prestazione più veloce ed accurata quando
la posizione della risposta corrisponde alla posizione dello stimolo anche se questa
non è rilevante per il compito. Il presente lavoro ha studiato l’emergere dell’effetto Simon
e il suo decorso temporale con stimoli visivi e risposte oculo-motorie utilizzando
un paradigma di tipo standard: stimoli e risposte condividevano infatti una relazione
anatomico-spaziale. I risultati hanno mostrato un effetto (1) ampio e significativo sia
nei tempi di reazione saccadici che negli errori e (2) con un decorso temporale descrescente,
supportando l’ipotesi che esso sia dovuto ad un meccanismo visuomotorio
The Effect of Luminance Condition on Form, Form-from-Motion and Motion Perception
Full text linkThis study investigated to what extent rod-dominated vision affects motion and form perception accuracy. Twenty-nine healthy subjects took part in the experiment. Form coherence (FC), form-from-motion (FFM) and motion coherence (MC) tests were assessed in low-light (rod-dominated vision) and high-light (cone-dominated vision) conditions. For each test we determined the accuracy by evaluating the correct detection obtained in five levels of coherence (corresponding to different signal-to-noise ratio). The results evidenced that motion, form and form-from-motion accuracy decreased in low-light condition. Furthermore, light condition effect was differently mediated by noise according to the type of task. The motion perception is affected only at high noise levels, while form discrimination was globally affected at all the levels, also in absence of noise, both for static (FC) and dynamic stimuli (FFM). We conclude that in rod-dominated vision form-from-motion perception is more defected than form and motion perception. We hypothesized that our results are due to the integration between M and P cells in FFM test increases the form perception accuracy in high-light condition but this advantage is completely lost during low-light condition, when the rods need to integrate information both from M and P cells
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