Abstract
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.
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.
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.
•Experiment 1& 2 show that anodal tDCS delivered (10 min at 1.5 mA) over the Fp3 reduces the face inversion effect.•Experiment 3 shows that the same tDCS stimulation does not have the same effect when applied to a different brain area.•Anodal tDCS to Fp3 brain area reduces face recognition.
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.
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.
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.
We review evidence that supports the conclusion that people can and do learn in two distinct ways – one associative, the other propositional. No one disputes that we solve problems by testing ...hypotheses and inducing underlying rules, so the issue amounts to deciding whether there is evidence that we (and other animals) also rely on a simpler, associative system, that detects the frequency of occurrence of different events in our environment and the contingencies between them. There is neuroscientific evidence that associative learning occurs in at least some animals (e.g., Aplysia californica), so it must be the case that associative learning has evolved. Since both associative and propositional theories can in principle account for many instances of successful learning, the problem is then to show that there are at least some cases where the two classes of theory predict different outcomes. We offer a demonstration of cue competition effects in humans under incidental conditions as evidence against the argument that all such effects are based on cognitive inference. The latter supposition would imply that if the necessary information is unavailable to inference then no cue competition should occur. We then discuss the case of unblocking by reinforcer omission, where associative theory predicts an irrational solution to the problem, and consider the phenomenon of the Perruchet effect, in which conscious expectancy and conditioned response dissociate. Further discussion makes use of evidence that people will sometimes provide one solution to a problem when it is presented to them in summary form, and another when they are presented in rapid succession with trial-by trial information. We also demonstrate that people trained on a discrimination may show a peak shift (predicted by associative theory), but given the time and opportunity to detect the relationships between S+ and S−, show rule-based behavior instead. Finally, we conclude by presenting evidence that research on individual differences suggests that variation in intelligence and explicit problem solving ability are quite unrelated to variation in implicit (associative) learning, and briefly consider the computational implications of our argument, by asking how both associative and propositional processes can be accommodated within a single framework for cognition.
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.
•Experiment 1a & 1b show that anodal tDCS delivered (10 min at 1.5 mA) at Fp3 reduces the behavioural face inversion effect .•The ERPs results show how the tDCS reduces the inversion effect on the N170 latencies and increases the inversion effect on the N170 amplitudes.
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.
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.
PDF
