Human faces are a special class of stimuli which we are expert at extracting relevant information from, such as gender, race, emotion and identity. Face individuation, despite requiring the complex ability to discriminate idiosyncratic features, can be performed within milliseconds from seeing a face. Although we are expert at face individuation, this expertise is reduced for racial outgroup faces. Other-race faces are individuated less accurately and more slowly than own-race faces, a phenomenon known as the Other-Race Effect (ORE). The ORE has received little attention in childhood and its neural time course has never been investigated in its obligatory and unconscious form in either adults or children. In this work, I focused on the implicit (i.e., outside of voluntary control) and unconscious (i.e., outside of awareness) impact of face racial belonging on face individuation. Specifically, I investigated how and when face individuation occurs for supraliminal and subliminal own- and other-race faces when identity and race processing is not explicitly requested or accessed. To this end, I conducted two studies using the priming paradigm combined with electroencephalographic (EEG) recording and Event-Related Potentials (ERPs) analysis. In Study 1, adults performed a priming paradigm while their electro-cortical activity was recorded. Participants were instructed to classify fully visible “target” faces, either Caucasian (own race) or Asian (other race), according to gender. Each target face was immediately preceded by a same-identity or a different-identity “prime” face, always sharing its race and gender. Critically, the prime face was either shown unmasked, i.e., visible, or masked, i.e., not visible. When the prime was visible, a priming effect, i.e., a facilitation of the target processing following an identical prime, emerged at the N100 ERP stage, for own- more than for other-race faces, and was present across later stages (N200, P300), more prominently for other- than own-race faces. When the prime was not visible, a priming effect emerged at the P300 stage, more prominent for other- than own-race faces. Differences could indicate a different individuation of own- and other-race faces shown consciously and unconsciously. In Study 2, school-aged children performed a priming paradigm while their electro-cortical activity was recorded. The paradigm was the same as in adults, but the prime was only presented masked (not visible). A priming effect emerged at the N100 ERP stage, irrespective of face race, and a race effect emerged at the N200 stage, irrespective of prime identity. The lack of face race influence on the priming effects could suggest comparable unconscious individuation of own- and other-race faces in school-aged children. As a study in progress, I am investigating the implicit neural face individuation in adults using a newly available paradigm, the sweep “oddball” fast periodic visual stimulation (FPVS), combined with electro-cortical activity recording and Steady State Visual Evoked Potentials (SSVEPs) analysis. In this paradigm, identical faces are periodically presented at decreasing frequency rates (20 to 5 Hz), whilst identity changes are introduced at a stable slower “oddball” frequency rate. If face individuation occurs, the neural response should synchronize to the oddball frequency. I expect this synchronization to emerge at different frequencies for Caucasian (own race) and Asian (other race) faces. Overall, this work provides original results that aim at elucidating the neural characterization of the implicit and unconscious impact of face racial belonging on face individuation in adults (Study 1, study in progress) and children (Study 2). Results help shed light on theoretical aspects of the ORE.

Il volto umano è uno stimolo speciale da cui siamo esperti a estrarre informazioni, come il genere, la razza, le emozioni e l’identità. La discriminazione dell’identità, nonostante richieda la complessa capacità di discernere caratteristiche idiosincratiche del volto, avviene in pochi millisecondi. Tuttavia, questa capacità è ridotta per volti appartenenti a razze diverse dalla propria. In genere, siamo più lenti e meno accurati a discriminare l’identità di volti di altre razze rispetto a volti della nostra, un fenomeno denominato “other-race” effect (ORE). L’ORE è stato poco studiato nei bambini, e il decorso temporale neurale dell’ORE nella sua forma implicita e inconscia non è mai stato esaminato in adulti o bambini. La presente tesi indaga come la razza influenza la discriminazione dell’identità a livello implicito (i.e., in assenza di controllo consapevole) e inconscio (i.e., in assenza di consapevolezza). In particolare, ho esaminato come e quando avviene la discriminazione dell’identità in volti supraliminali e subliminali della propria e dell’altra razza quando l’elaborazione di identità e razza non sono esplicitamente richieste. Allo scopo, ho condotto due studi utilizzando un paradigma di priming combinato con la registrazione dell’attività elettroencefalografica (EEG) e dei Potenziali Evento-Relati (ERPs). Nello Studio 1, ai partecipanti adulti è stato chiesto di classificare volti “target”, caucasici (propria razza) o asiatici (altra razza), in base al genere. Ogni volto target era preceduto da un volto “prime” della sua stessa identità o di diversa identità, ma del suo stesso genere e razza. Il volto prime era mostrato non mascherato (visibile) o mascherato (non visibile). Quando il prime era visibile, un effetto di priming, i.e., facilitazione dell’elaborazione del target preceduto da un prime identico, è emerso sulla componente N100, in misura maggiore per la propria che per l’altra razza, e su componenti più tardive (N200, P300), in misura maggiore per l’altra che per la propria razza. Quando il prime non era visibile, l’effetto di priming è emerso sulla P300, maggiormente per l’altra che per la propria razza. Tali risultati suggeriscono una diversa discriminazione dell’identità in volti della propria e dell’altra razza elaborati consciamente e inconsciamente. Nello Studio 2, bambini in età scolare hanno svolto lo stesso compito, ma a differenza degli adulti, il prime compariva solo mascherato (non visibile). Un effetto di priming è emerso sulla componente N100, indipendentemente dalla razza, e un effetto della razza è emerso sulla N200, indipendentemente dall’identità del prime. Tali risultati suggeriscono una simile discriminazione inconscia dell’identità dei volti della propria e dell’altra etnia nei bambini in età scolare. In uno studio in corso, indago la discriminazione implicita dell’identità negli adulti utilizzando un nuovo paradigma, lo sweep “oddball” fast periodic visual stimulation (FPVS), combinato con la registrazione EEG e degli Steady State Visual Evoked Potentials (SSVEPs). In questo compito, volti identici sono ripetuti periodicamente a una frequenza decrescente (20-5Hz) e cambi di identità appaiono sempre alla stessa frequenza “oddball” più lenta. La discriminazione dell’identità comporta una sincronizzazione della risposta neurale alla frequenza di presentazione degli oddball. Prevedo che la sincronizzazione emerga a diverse frequenze per volti caucasiaci (propria razza) e asiatici (altra razza). In breve, la presente tesi fornisce risultati originali volti a chiarire i correlati neurali dell’influenza della razza sulla discriminazione dell’identità a livello implicito e inconscio in adulti (Studio 1, Studio in corso) e bambini (Studio 2). I risultati aiutano a far luce su aspetti teorici dell’ORE.

ELABORAZIONE IMPLICITA DELL’IDENTITÀ DEI VOLTI DELLA PROPRIA E DI ALTRE ETNIE: DINAMICHE TEMPORALI NEURALI IN ADULTI E BAMBINI / Luana Serafini , 2023 Mar 31. 34. ciclo, Anno Accademico 2020/2021.

ELABORAZIONE IMPLICITA DELL’IDENTITÀ DEI VOLTI DELLA PROPRIA E DI ALTRE ETNIE: DINAMICHE TEMPORALI NEURALI IN ADULTI E BAMBINI

SERAFINI, LUANA
2023

Abstract

Human faces are a special class of stimuli which we are expert at extracting relevant information from, such as gender, race, emotion and identity. Face individuation, despite requiring the complex ability to discriminate idiosyncratic features, can be performed within milliseconds from seeing a face. Although we are expert at face individuation, this expertise is reduced for racial outgroup faces. Other-race faces are individuated less accurately and more slowly than own-race faces, a phenomenon known as the Other-Race Effect (ORE). The ORE has received little attention in childhood and its neural time course has never been investigated in its obligatory and unconscious form in either adults or children. In this work, I focused on the implicit (i.e., outside of voluntary control) and unconscious (i.e., outside of awareness) impact of face racial belonging on face individuation. Specifically, I investigated how and when face individuation occurs for supraliminal and subliminal own- and other-race faces when identity and race processing is not explicitly requested or accessed. To this end, I conducted two studies using the priming paradigm combined with electroencephalographic (EEG) recording and Event-Related Potentials (ERPs) analysis. In Study 1, adults performed a priming paradigm while their electro-cortical activity was recorded. Participants were instructed to classify fully visible “target” faces, either Caucasian (own race) or Asian (other race), according to gender. Each target face was immediately preceded by a same-identity or a different-identity “prime” face, always sharing its race and gender. Critically, the prime face was either shown unmasked, i.e., visible, or masked, i.e., not visible. When the prime was visible, a priming effect, i.e., a facilitation of the target processing following an identical prime, emerged at the N100 ERP stage, for own- more than for other-race faces, and was present across later stages (N200, P300), more prominently for other- than own-race faces. When the prime was not visible, a priming effect emerged at the P300 stage, more prominent for other- than own-race faces. Differences could indicate a different individuation of own- and other-race faces shown consciously and unconsciously. In Study 2, school-aged children performed a priming paradigm while their electro-cortical activity was recorded. The paradigm was the same as in adults, but the prime was only presented masked (not visible). A priming effect emerged at the N100 ERP stage, irrespective of face race, and a race effect emerged at the N200 stage, irrespective of prime identity. The lack of face race influence on the priming effects could suggest comparable unconscious individuation of own- and other-race faces in school-aged children. As a study in progress, I am investigating the implicit neural face individuation in adults using a newly available paradigm, the sweep “oddball” fast periodic visual stimulation (FPVS), combined with electro-cortical activity recording and Steady State Visual Evoked Potentials (SSVEPs) analysis. In this paradigm, identical faces are periodically presented at decreasing frequency rates (20 to 5 Hz), whilst identity changes are introduced at a stable slower “oddball” frequency rate. If face individuation occurs, the neural response should synchronize to the oddball frequency. I expect this synchronization to emerge at different frequencies for Caucasian (own race) and Asian (other race) faces. Overall, this work provides original results that aim at elucidating the neural characterization of the implicit and unconscious impact of face racial belonging on face individuation in adults (Study 1, study in progress) and children (Study 2). Results help shed light on theoretical aspects of the ORE.
IMPLICIT IDENTITY CODING FROM OWN- AND OTHER-RACE FACES: BRAIN TEMPORAL DYNAMICS IN ADULTS AND CHILDREN
31-mar-2023
PESCIARELLI, Francesca
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