Using transcranial direct current stimulation (tDCS) to selectively modulate the face inversion effect and N170 event-related potentials.

We report a large study (n = 72) using combined transcranial direct current stimulation-electroencephalography (tDCS-EEG) to investigate the modulation of perceptual learning indexed by the face inversion effect. Participants were engaged with an old/new recognition task involving intermixed upright and inverted, normal and Thatcherized faces. The accuracy results showed anodal tDCS delivered at the Fp3 scalp area (cathode/reference electrode placed at Fp2) increased the behavioural inversion effect for normal faces versus sham/control and this covaried with a modulation of the N170 event-related potential component. A reduced inversion effect for normal faces was found on the N170 latency and amplitude versus sham/control, extending recent work that combined tDCS and EEG in circumstances where the behavioural face inversion effect was reduced. Our results advance understanding of the neural mechanisms responsible for perceptual learning by revealing a dissociation between the N170 amplitude and latency in response to the tDCS-induced modulation of the face inversion effect. The behavioural modulation of the inversion effect tracks the modulation of the N170 amplitudes, albeit it is negatively correlated (i.e., reduced inversion effect-larger N170 amplitude inversion effect, increased inversion effect-reduced N170 amplitude inversion effect). For the N170 latencies, the inversion effect is reduced by the tDCS protocol we use irrespective of any modulation of the behavioural inversion effect.

Modulating perceptual learning indexed by the face inversion effect: Simulating the application of transcranial direct current stimulation using the MKM model.

We report here two large studies investigating the effects of an established transcranial direct current stimulation (tDCS) procedure on perceptual learning as indexed by the face inversion effect. Experiments 1a and 1b (n = 128) examined the harmful generalization from Thatcherized faces to normal faces by directly comparing the size of the inversion effect for normal faces when presented intermixed with Thatcherized faces (Experiment 1a) versus that obtained when normal faces were presented intermixed with checkerboards (Experiment 1b). The results from the sham/control tDCS groups provide the first direct evidence in the literature showing how Thatcherized faces generalize onto normal ones producing a reduced inversion effect compared to when normal faces are presented with stimuli (e.g., checkerboards) that do not generalize significantly to normal faces. In the anodal tDCS groups, this effect was reversed, with a larger inversion effect recorded for normal faces in Experiment 1a versus that found in Experiment 1b. Further analyses within each experiment confirmed that the anodal tDCS procedure can enhance the inversion effect for normal faces in circumstances where harmful generalization would otherwise be produced by the Thatcherized faces (Experiment 1a). We also demonstrated our standard reduction in the inversion effect for normal faces consequent on the application of tDCS when presented intermixed with stimuli that do not generalize onto them. We interpret our results in terms of simulations using the MKM model of perceptual and associative learning. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Transcranial direct current stimulation (tDCS) eliminates the other-race effect (ORE) indexed by the face inversion effect for own versus other-race faces.

We investigate here individuals' reduced ability to recognise faces from other racial backgrounds, a robust phenomenon named the other-race effect (ORE). In this literature the term "race" is used to refer to visually distinct ethnic groups. In our study, we will refer to two of such groups: Western Caucasian (also known as White European) and East Asian e.g., Chinese, Japanese, Korean. This study applied the tDCS procedure (double-blind, 10 min duration, 1.5 mA intensity, targeting Fp3 location), developed in the perceptual learning literature, specifically used to remove the expertise component of the face inversion effect (FIE), which consists of higher recognition performance for upright than inverted faces. In the tDCS-sham condition (N = 48) we find a robust ORE i.e., significantly larger FIE for own versus other-race faces due to higher performance for upright own-race faces. Critically, in the anodal-tDCS condition (N = 48) the FIE for own-race faces was significantly reduced compared to sham due to impaired performance for upright faces thus eliminating the cross-race interaction index of the ORE. Our results support the major role that perceptual expertise, manifesting through perceptual learning, has in determining the ORE indexed by the FIE.

Using transcranial direct current stimulation (tDCS) to influence decision criterion in a target detection paradigm.

In this article we investigate how a psychological theory used to model perceptual learning and face recognition can be used to predict that anodal tDCS delivered over the DLPFC at Fp3 site (for 10 mins duration at 1.5 mA intensity) modulates the decision criterion, C, (and not d-prime [d']) in a target detection task. In two between-subjects and double-blind experiments (n = 112) we examined the tDCS effects on C when subjects were engaged in a target detection task, in the first instance involving artificial checkerboard stimuli (Experiment 1a), and subsequently face stimuli (Experiment 1b). The results from both experiments revealed that in the sham/control groups a significantly higher C was used when detecting a target pattern (Experiment 1a) or face (Experiment 1b) presented on a familiar rather than a random background. Importantly, anodal tDCS significantly reduced/reversed this difference between C adopted for familiar and random backgrounds in both Experiment 1a and 1b without affecting d'. These results contribute to advance our understanding of the tDCS-induced effects on stimulus representation and to the literature regarding the modulation of C. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Using transcranial Direct Current Stimulation (tDCS) to investigate why faces are and are not special.

We believe we are now in a position to answer the question, "Are faces special?" inasmuch as this applies to the face inversion effect (better performance for upright vs inverted faces). Using a double-blind, between-subject design, in two experiments (n = 96) we applied a specific tDCS procedure targeting the Fp3 area while participants performed a matching-task with faces (Experiment 1a) or checkerboards from a familiar prototype-defined category (Experiment 1b). Anodal tDCS eliminated the checkerboard inversion effect reliably obtained in the sham group, but only reduced it for faces (although the reduction was significant). Thus, there is a component to the face inversion effect that we are not affecting with a tDCS procedure that can eliminate the checkerboard inversion effect. We suggest that the reduction reflects the loss of an expertise-based component in the face inversion effect, and the residual is due to a face-specific component of that effect.

Special issue on recent advances in perceptual learning.

This is an introduction to the special issue "Perceptual Learning." This collection of studies reflects some of the interesting new discoveries being made in the study of perceptual learning. Although much headway has been made toward understanding the basic phenomena, this collection of studies makes clear that there is much that remains to be understood. The study of perceptual learning continues to be a fruitful area of research, and it is our hope that this collection, like the Exeter workshop that it was based on, will continue to inspire future research efforts. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Latent inhibition in young children: A developmental effect?

Previous research by Kaniel & Lubow in 1986 found that young children (aged 4-5 years) exhibited poorer learning (latent inhibition) to preexposed stimuli than older children (aged 7-10 years). The aim of our research was to develop a computer-based, child-friendly study that would replicate and extend the work of Kaniel & Lubow in a way that ruled out other, attention-based explanations of their effect. One hundred and four children and 32 undergraduate students took part in our experiment. This consisted of a preexposure/study phase in which participants were asked to press computer keys in response to clipart pictures of animals and dinosaurs. Each animal or dinosaur picture was preceded by one of 2 "warning signals" that acted as the preexposed stimuli (to which no response was required). In the test phase that followed, the participants had to either press the spacebar or withhold their response to each preexposed stimulus and two novel stimuli. They learned which response was correct by trial and error using the feedback provided. The accuracy and reaction time (RT) of the responses during the test phase were analyzed and indicated that the youngest children showed significantly lower mean accuracy and longer mean response times to the preexposed stimuli than to stimuli they had not been preexposed to. In contrast, the older children showed no significant differences in their responses to preexposed and novel stimuli. These results are consistent with those found by Kaniel & Lubow and as such provide additional evidence for latent inhibition in young children. We discuss the implications for theories of perceptual learning in humans. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The effects of transcranial direct current stimulation on perceptual learning for upright faces and its role in the composite face effect.

In the 3 experiments reported here we show that a specific neurostimulation method, whose influence can be understood in terms of a well-known theory of stimulus representation, is able to affect face recognition skills by impairing participants' performance for upright faces. We used the transcranial Direct Current Stimulation (tDCS) procedure we have recently developed that allows perceptual learning, as indexed by the face inversion effect, to be modulated. We extended this tDCS procedure to another phenomenon, the composite face effect, which constitutes better recognition of the top half of an upright face when conjoined with a congruent (in terms of the response required) rather than incongruent bottom half. All three experiments used the Face-Matching task traditionally used to study this phenomenon. Experiment 1a (n = 48) showed that anodal tDCS (using a double-blind between-subjects design) delivered at Fp3 (10 mins at 1.5 mA) affected overall performance for upright faces compared with sham but had no effect on the composite face effect itself. Experiment 1b (n = 48) replicated our usual tDCS-induced effects on the face inversion effect but this time using a Face-Matching task instead of the old/new recognition task previously used to obtain the effect. Experiment 2 (n = 72) replicated the findings from Experiment 1a, and, using an active control group, showed that the Fp3 anodal tDCS effects on performance to upright faces are not obtained when a different brain area is targeted. We interpret our results in the light of previous literature on the tDCS effects on perceptual learning and face recognition and suggest that different mechanisms are involved in the face inversion effect and the composite face effect. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Testing the effects of transcranial direct current stimulation (tDCS) on the face inversion effect and the N170 event-related potentials (ERPs) component.

The following study investigates the effects of tDCS on face recognition skills indexed by the face inversion effect (better recognition performance for upright vs. inverted faces). We combined tDCS and EEG simultaneously to examine the effects of tDCS on the face inversion effect behaviourally and on the N170 ERPs component. The results from two experiments (overall N = 112) show that anodal tDCS delivered at Fp3 site for 10 min at 1.5 mA (double-blind and between-subjects) can reduce behaviourally the face inversion effect compared to sham (control) stimulation. The ERP results provide some evidence for tDCS being able to influence the face inversion effect on the N170. Specifically, we find a dissociation of the tDCS-induced effects where for the N170 latencies the tDCS reduces the usual face inversion effect (delayed N170 in response to inverted vs. upright faces) compared to sham. Contrarily, the same tDCS procedure on the same participants increased the inversion effect seen in the N170 amplitudes by making the negative deflection for the inverted faces that much greater than that for upright faces. We interpret our results in the context of the literature on the face inversion effect and the N170 peak component. In doing so, we extend our results to previous studies investigating the effects of tDCS on perceptual learning and face recognition.

Directional cues and landmark configurations: The effect of rotating one set of landmarks relative to another.

In this article we addressed the question whether rats can use distal landmarks as directional cues that are used in combination with other proximal landmark configurations. The animals were trained with an A, B, C, and D landmark configuration in the Morris pool, where B and C are the near (to platform) landmarks and A and D the far ones. We also added another more distal "directional" cue Z (a white strip attached to the black curtain surrounding the pool). Experiment 1a shows a robust detrimental effect on the time spent by the rats swimming in the platform quadrant when the location of all landmarks was "Inverted" (rotated by 180 degrees) with respect to Z. A similar detrimental effect was found when, after the inversion manipulation, the locations of the near and far landmarks were "Flipped" (B swapped with C and A with D). Rats in both Inverted and Flipped tests spent more time in the Z quadrant compared to the platform quadrant (BC). Experiment 1b provided evidence distinguishing between alternative explanations of how the directional cue Z acts in combination with the other landmarks. The results from both experiments show that Z operates differently to the standard landmarks. It can function as a beacon in its own right. It can also combine with the other landmarks to produce a high level of search performance, in a way that we hypothesize to be distinct from that described by the configural analysis often applied to multiple landmarks. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The effect of tDCS on recognition depends on stimulus generalization: Neuro-stimulation can predictably enhance or reduce the face inversion effect.

This article reports results from three experiments that investigate how a particular neuro-stimulation procedure is able, in certain circumstances, to selectively increase the face inversion effect by enhancing recognition for upright faces, and argues that these effects can be understood in terms of the McLaren-Kaye-Mackintosh (MKM) theory of stimulus representation. We demonstrate how a specific transcranial direct current stimulation (tDCS) methodology can improve performance in circumstances where error-based salience modulation is making face recognition harder. The 3 experiments used an old/new recognition task involving sets of normal versus Thatcherized faces. The main characteristic of Thatcherized faces is that the eyes and the mouth are upside down, thus emphasizing features that tend to be common to other Thatcherized faces and so leading to stronger generalization making recognition worse. Experiment 1 combined a behavioral and event-related potential study looking at the N170 peak component, which helped us to calibrate the set of face stimuli needed for subsequent experiments. In Experiment 2, we used our tDCS procedure (between-subjects and double-blind) in an attempt to reduce the negative effects induced by error-based modulation of salience on recognition of upright Thatcherized faces. Results largely confirmed our predictions. In addition, they showed a significant improvement on recognition performance for upright normal faces. Experiment 3 provides the first direct evidence in a single study that the same tDCS procedure is able to both enhance performance when normal faces are presented with Thatcherized faces, and to reduce performance when normal faces are presented with other normal faces (i.e., male vs. female faces). We interpret our results by analyzing how salience modulation influences generalization between similar categories of stimuli. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The role of experience-based perceptual learning in the face inversion effect.

Perceptual learning of the type we consider here is a consequence of experience with a class of stimuli. It amounts to an enhanced ability to discriminate between stimuli. We argue that it contributes to the ability to distinguish between faces and recognize individuals, and in particular contributes to the face inversion effect (better recognition performance for upright vs inverted faces). Previously, we have shown that experience with a prototype defined category of checkerboards leads to perceptual learning, that this produces an inversion effect, and that this effect can be disrupted by Anodal tDCS to Fp3 during pre-exposure. If we can demonstrate that the same tDCS manipulation also disrupts the inversion effect for faces, then this will strengthen the claim that perceptual learning contributes to that effect. The important question, then, is whether this tDCS procedure would significantly reduce the inversion effect for faces; stimuli that we have lifelong expertise with and for which perceptual learning has already occurred. Consequently, in the experiment reported here we investigated the effects of anodal tDCS at Fp3 during an old/new recognition task for upright and inverted faces. Our results show that stimulation significantly reduced the face inversion effect compared to controls. The effect was one of reducing recognition performance for upright faces. This result is the first to show that tDCS affects perceptual learning that has already occurred, disrupting individuals' ability to recognize upright faces. It provides further support for our account of perceptual learning and its role as a key factor in face recognition.

Labelling faces as 'Autistic' reduces the inversion effect.

Does the belief that a face belongs to an individual with autism affect recognition of that face? To address this question, we used the inversion effect as a marker of face recognition. In Experiment 1, participants completed a recognition task involving upright and inverted faces labelled as either 'regular' or 'autistic'. In reality, the faces presented in both conditions were identical. Results revealed a smaller inversion effect for faces labelled as autistic. Thus, simply labelling a face as 'autistic' disrupts recognition. Experiment 2 showed a larger inversion effect after the provision of humanizing versus dehumanizing information about faces labelled as 'autistic'. We suggest changes in the inversion effect could be used as a measure to study stigma within the context of objectification and dehumanization.

The effect of scrambling upright and inverted faces on the N170.

The face inversion effect refers to a decrement in performance when we try to recognise familiar faces turned upside down (inverted), compared with familiar faces presented in their usual (upright) orientation. Recently, we have demonstrated that the inversion effect can also be found with checkerboards drawn from prototype-defined categories when the participants have been trained with these categories, suggesting that factors such as expertise and the relationships between stimulus features may be important determinants of this effect. We also demonstrated that the typical inversion effect on the N170 seen with faces is found with checkerboards, suggesting that modulation of the N170 is a marker for disruption in the use of configural information. In the present experiment, we first demonstrate that our scrambling technique greatly reduces the inversion effect in faces. Following this, we used Event-Related Potentials ( ERPs) recorded while participants performed an Old/New recognition study on normal and scrambled faces presented in both upright and inverted orientations to investigate the impact of scrambling on the N170. We obtained the standard robust inversion effect for normal faces: The N170 was both larger and delayed for normal inverted faces as compared with normal upright faces, whereas a significantly reduced inversion effect was recorded for scrambled faces. These results show that the inversion effect on the N170 is greater for normal compared with scrambled faces, and we interpret the smaller effect for scrambled faces as being due to the reduction in expertise for those faces consequent on scrambling.

How we can change your mind: Anodal tDCS to Fp3 alters human stimulus representation and learning.

The aim of the current work is to advance our understanding of both the mechanisms controlling perceptual learning and the face inversion effect. In the three double blind experiments reported here (total N = 144) we have shown that anodal tDCS stimulation (10 min at 1.5 mA) delivered over the left DLPFC at Fp3 affects perceptual learning and drastically reduces the, usually robust, face inversion effect. In Experiment 1, we found a significantly reduced inversion effect in the anodal group compared to that in the sham group. Experiment 2 replicated the pattern of results found in Experiment 1. In both experiments recognition performance for upright faces in the anodal group was significantly impaired compared to that in the sham group. Finally, using an active control in Experiment 3 (same behavioural task but different tDCS targeted brain area) we showed that the same Fp3 anodal tDCS stimulation effect is not obtained when a different brain area is targeted.

Students Wearing Police Uniforms Exhibit Biased Attention toward Individuals Wearing Hoodies.

Police provide an essential public service and they often operate in difficult circumstances, requiring high-speed cognition. Recent incidents involving apparent profiling and aggressive behavior have led to accusations that the police are sometimes biased. Given that previous research has shown a link between clothing and cognition, we investigated the question of whether the police uniform itself might induce a bias in social attention. To address this question, and using a Canadian university student sample, we assessed whether wearing a police uniform biases attention toward black faces compared to white faces, and low-status individuals compared to high-status individuals. In Experiment 1 (n = 28), participants wore either a police-style uniform or mechanic overalls, and performed a shape categorization task in the presence of a distractor that could be either: a black face, a white face, a person wearing a hoodie (whom we propose will be associated with low SES), or a person wearing a suit (whom we propose will be associated with high SES). Participants wearing the police-style uniform exhibited biased attention, indexed by slower reaction times (RTs), in the presence of low-SES images. In Experiment 2 (n = 28), we confirmed this bias using a modified Dot-Probe task - an alternate measure of attentional bias in which we observed faster RTs to a dot probe that was spatially aligned with a low SES image. Experiment 3 (n = 56) demonstrated that attentional bias toward low-SES targets appears only when participants wear the police-style uniform, and not when they are simply exposed to it - by having it placed on the desk in front of them. Our results demonstrate that wearing a police-style uniform biases attention toward low-SES targets. Thus, wearing a police-style uniform may induce a kind of "status-profiling" in which individuals from low-status groups become salient and capture attention. We note that our results are limited to university students and that it will be important to extend them to members of the community and law-enforcement officers. We discuss how uniforms might exert their effects on cognition by virtue of the power and cultural associations they evoke in the wearer.

Switching off perceptual learning: Anodal transcranial direct current stimulation (tDCS) at Fp3 eliminates perceptual learning in humans.

Perceptual learning can be acquired as a result of experience with stimuli that would otherwise be difficult to tell apart, and is often explained in terms of the modulation of feature salience by an error signal based on how well that feature can be predicted by the others that make up the stimulus. In this article we show that anodal transcranial Direct Current Stimulation (tDCS) at Fp3 directly influences this modulation process so as to eliminate and possibly reverse perceptual learning. In 2 experiments, anodal stimulation disrupted perceptual learning (indexed by an inversion effect) compared with sham (Experiment 1) or cathodal (Experiment 2) stimulation. Our findings can be interpreted as showing that anodal tDCS severely reduced or even abolished the modulation of salience based on error, greatly increasing generalization between stimuli. This result supports accounts of perceptual learning based on variations in salience as a consequence of pre-exposure, and opens up the possibility of controlling this phenomenon. (PsycINFO Database Record

The Face Inversion Effect: Roles of First- and Second-Order Configural Information.

The face inversion effect (FIE) is a reduction in recognition performance for inverted faces compared with upright faces. Several studies have proposed that a type of configural information, called second-order relational information, becomes more important with increasing expertise and gives rise to the FIE. However, recently it has been demonstrated that it is possible to obtain an FIE with facial features presented in isolation, showing that configural information is not necessary for this effect to occur. In this article we test whether there is a role for configural information in producing the FIE and whether second- or first-order relational information is particularly important. In Experiment 1, we investigated the role of configural information and local feature orientation by using a new type of "Thatcherizing" transformation on our set of faces, aiming to disrupt second-order and local feature orientation information but keeping all first-order properties unaltered. The results showed a significant reduction in the FIE for these "new" Thatcherized faces, but it did not entirely disappear. Experiment 2 confirmed the FIE for new Thatcherized faces, and Experiment 3 establishes that both local feature orientation and first-order relational information have a role in determining the FIE.

Towards a Mechanistic Understanding of the Effects of Body Posture on Facial Emotion Categorization.

This study investigated the causes of the face-body congruence effect (FBCE), which refers to the advantage in performance when participants are asked to categorize emotional faces compounded with emotional matching body postures (congruent) compared with incongruent face-body compound stimuli (body postures mismatching the facial emotions). Experiment 1 showed that manipulations aiming to alter holistic processing significantly reduced the FBCE. In particular, the disruption of holistic processing affected significantly the performance for congruent composites. However, no effect was obtained on the incongruent stimuli. In Experiment 2, the inversion manipulation showed a clear disadvantage for incongruent stimuli brought by the disruption of the single feature orientation information. Thus, we found confirmation of the different processing involved in perceiving congruent and incongruent stimuli. Finally, Experiment 3 confirmed that we are able to reduce entirely the FBCE when the orientation of the units (the face and the body) constituting the incongruent composites is matched.

Perceptual learning and inversion effects: Recognition of prototype-defined familiar checkerboards.

The face inversion effect is a defection in performance in recognizing inverted faces compared with faces presented in their usual upright orientation typically believed to be specific for facial stimuli. McLaren (1997) was able to demonstrate that (a) an inversion effect could be obtained with exemplars drawn from a familiar category, such that upright exemplars were better discriminated than inverted exemplars; and (b) that the inversion effect required that the familiar category be prototype-defined. In this article, we replicate and extend these findings. We show that the inversion effect can be obtained in a standard old/new recognition memory paradigm, demonstrate that it is contingent on familiarization with a prototype-defined category, and establish that the effect is made up of two components. We confirm the advantage for upright exemplars drawn from a familiar, prototype-defined category, and show that there is a disadvantage for inverted exemplars drawn from this category relative to suitable controls. We also provide evidence that there is an N170 event-related potential signature for this effect. These results allow us to integrate a theory of perceptual learning originally proposed by McLaren, Kaye, and Mackintosh (1989) with explanations of the face inversion effect, first reported by Yin.