Florence Benoit-Moreau
email: benoit_florence@hotmail.com

Béatrice Parguel
email: beatrice.parguel@gmail.com

Building Brand Equity with Environmental Communication: An empirical investigation in France Classification: Research paper

Keywords: CSR communication, environmental communication, brand equity, congruency, societal consciousness

 brand equity framework, this paper investigates the impact of the firm's environmental communication on brand equity, and specifically its impact on brand image, through the strength and favourability of brand environmental associations.

Design/methodology/approach

A between-subjects experimental design tests the hypotheses with a generalisable sample of 165 French consumers.

Originality/value of paper

Despite existing research on corporate social responsibility (CSR), no studies focus on the specific impact of CSR communication on brand equity. This research provides initial empirical evidence about the positive effect of environmental claims on customer-based brand equity.

Findings

Environmental communication positively influences the strength and favourability of brand environmental associations, therefore improving brand equity. Two moderators reinforce the impact of environmental communication on brand equity through the strength of brand environmental associations: the perceived congruence between the brand and the cause, and the perceived credibility of the claim.

Practical implications

In the context of greater consumer pressure regarding business ethics, managers should favour environmental arguments in their corporate communication to improve brand image through societal associations. Doing so, they should focus their communication on causes that are congruent with their brands to facilitate brand equity building, and ensure they are credible when proclaiming these arguments.

Introduction

The interest for corporate social responsibility (CSR), born 50 years ago [START_REF] Bowen | Social Responsibilities of the Businessman[END_REF], is strongly enhanced today as many companies and brands communicate about their societal initiatives in Europe. Among these societal claims, environmental ones dominate as ecology is the most typical domain of CSR [START_REF] Mohr | Do Consumers Expect Companies to be Socially Responsible. The Impact of Corporate Social Responsibility on Buying Behavior[END_REF], and because some of them (like climate change) have achieved a tremendous media coverage [START_REF] Peattie | Climate Change: A Social and Commercial Marketing Communications Challenge[END_REF]. In Europe, many brands use environmental claims in their ads. For example, in France in 2007, 3% of mass media advertisements included messages about company actions to protect the environment, a threefold increase compared with 2006 (ARPP-Ademe, 2008). Such environmental communication practices develop, following consumers' growing societal awareness. In France, 68% of consumers think firms should pay more attention to the impact of their actions on the environment and social harmony (Sociovision 2005 Survey) and 54% consider the environmental-friendly attribute as a very important criterion when choosing a product (IFOP 2008in Le Monde, June 3, 2008).

From a strategical point of view, environmental communication practices take different forms from simply providing brief and general information, to turning firms' involvement into the heart of brand positioning (e.g., The Body Shop, Natura Brasil, Ben & Jerry's or Stonyfield Farm, for which environmental involvement is the corner stone of their mission statement). In practice, firms usually advertise their environmental involvement through corporate or brand Web sites, relationship marketing tools (e.g., newsletters, consumer magazines, catalogues) or mass-media advertising (e.g., Carrefour and its outdoor advertising campaigns in France).

In a context where consumers challenge brands added value and become more critical, societal initiatives and therefore communication about them appear as a key strategic lever to build brand equity [START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF]. Recent empirical works of research have studied the impact of the firm's societal initiatives (whether environmental or social) on consumers. They generally demonstrate a positive impact on the attitude towards the product or the firm and on consumers' purchase intent [START_REF] Brown | The Company and the Product: Corporate Associations and Consumer Product Responses[END_REF][START_REF] Creyer | The Influence of Firm Behavior on Purchase Intention: Do Consumers Really Care about Business Ethics?[END_REF][START_REF] Murray | Using a Hierarchy-of-Effects Approach to Gauge the Effectiveness of Corporate Social Responsibility to Generate Goodwill toward the Firm: Financial versus Nonfinancial Impacts[END_REF][START_REF] Folkes | Effects of Information about Firms' Ethical and Unethical Actions on Consumers' Attitudes[END_REF][START_REF] Ellen | Charitable Programs and the Retailer: Do they Mix?[END_REF][START_REF] Mohr | Do Consumers Expect Companies to be Socially Responsible. The Impact of Corporate Social Responsibility on Buying Behavior[END_REF][START_REF] Sen | Does Doing Good Always Lead to Doing Better? Consumer Reactions to Corporate Social Responsibility[END_REF]Swaen andVanhamme, 2004, 2005;[START_REF] Mohr | The Effects of Corporate Social Responsibility and Price on Consumer Responses[END_REF]. Furthermore, while several academic studies have proposed that societal initiatives and related communication can actively build brand equity [START_REF] Hoeffler | Building Brand Equity through Corporate Societal Marketing[END_REF][START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF]Bhattacharya et al., 2004), none have tested it yet. Filling this gap is important: building brand equity is still a major marketing issue as it increases marketing-mix efficiency, as well as the probability of success of brand extensions [START_REF] Keller | Conceptualizing, Measuring, and Managing Customer-Based Brand Equity[END_REF][START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF][START_REF] Erdem | Brand Equity as a Signaling Phenomenon[END_REF].

Therefore, in this paper, we propose that societal communication, and more specifically environmental communication, contributes to brand equity building. We derive hypotheses from [START_REF] Keller | Conceptualizing, Measuring, and Managing Customer-Based Brand Equity[END_REF][START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF] brand equity framework and experimentally test them in the case of a corporate brand. The study shows that environmental communication generally increases brand equity, and also assesses the influence of situational variables on brand equity building, such as the perceived congruency between the brand and the cause supported, and the perceived credibility of the environmental claim. The following section reviews the literature on the concepts of CSR and societal communication, and on their effects on consumers' response. Next, the paper presents the conceptual framework, the experimental methodology and its results, and finally discusses its implications and limitations, and potential routes for future research.

Literature review

CSR and CSR communication

CSR covers a vast field of research (e.g., history, strategy, risk management, marketing, accounting/auditing/reporting, human resources), and definitions abound. In a broad perspective, CSR aims at "achieving commercial success in ways that honour ethical values and respect people, communities and the natural environment" (Bhattacharya and Sen, 2004, p.13). This conceptualisation includes a lot of practices and denominations: corporate societal marketing [START_REF] Hoeffler | Building Brand Equity through Corporate Societal Marketing[END_REF], business ethics [START_REF] Creyer | The Influence of Firm Behavior on Purchase Intention: Do Consumers Really Care about Business Ethics?[END_REF] or causerelated marketing [START_REF] Ellen | Charitable Programs and the Retailer: Do they Mix?[END_REF]. To circumscribe these various practices, this paper adopts a generic typology of CSR dimensions, making a distinction between environmental (how a business uses natural resources) and social responsibilities (how a business relates to the community in which it operates), and actually focuses on one of these dimensions: the environmental one. It follows the European Commission definition of CSR as "the voluntary integration of social and environmental concerns in the enterprises' daily business operations and in the interaction with their stakeholders" (DG Enterprise, Observatory of European SMEs, Report 2002 / No. 4: European SMEs and Social and Environmental Responsibility). Indeed, since the 90's, the study of CSR has been inscribed in the general stakeholder theory [START_REF] Clarkson | A Stakeholder Framework for Analyzing and Evaluating Corporate Social Performance[END_REF][START_REF] Donaldson | The Stakeholder Theory of the Corporation: Concepts, Evidence, and Implications[END_REF][START_REF] Murray | Using a Hierarchy-of-Effects Approach to Gauge the Effectiveness of Corporate Social Responsibility to Generate Goodwill toward the Firm: Financial versus Nonfinancial Impacts[END_REF], stating that firms allocate their resources and make decisions in order to satisfy stakeholders (e.g., shareholders, lobbies, employees, consumers). Though largely ignored as stakeholders so far, consumers are now under focus, as they become a more critical and powerful pressure group under the influence of consumer movements and non-governmental organisations (NGOs). This interest for consumers as a strategic target can explain the development of CSR communication, which appears to be a key lever to provide more information regarding CSR practices.

As an aspect of corporate communication, CSR communication "is designed and distributed by the company itself about its CSR efforts" (Morsing, 2006, p.171) and can reflect three potential approaches [START_REF] Van De Ven | An Ethical Framework for the Marketing of Corporate Social Responsibility[END_REF]. The reputation management approach focuses "on the basic requirements of conducting a responsible business to obtain and maintain a license to operate from society" (Van de Ven, 2008, p.345) and implies no explicit CSR communication. The second approach, building a virtuous corporate brand, means making an "explicit promise to the stakeholders and the general public that the corporation excels with respect to their CSR endeavours" (Van de Ven, 2008, p.345), which clearly suggests CSR communication. In this sense, two communication instruments are available (Van de Ven, 2008): corporate communication instruments (e.g., CSR reporting, publication of ethical codes, Web sites) and marketing communication instruments (e.g., advertising, sponsoring, direct marketing and promotions, public relations). The latter, which can be overly salient, are riskier and therefore remain less common, despite some recent rapid growth.

The third, ethical product differentiation approach means "differentiating a certain product or service on the basis of an environmental or social quality" (Van de Ven, 2008, p.348). In this case, CSR efforts constitute the heart of brand positioning (e.g., The Body Shop, Natura Brasil), which makes CSR communications natural and inevitable. Although managers have long followed the principle: Do good and let other talk about it [START_REF] Kotler | Corporate Social Responsibility. Doing the Most Good for your Company and your Cause[END_REF], the use of CSR communication is growing, because it provides a corporate marketing tool that can build a strong corporate image and reputation [START_REF] Hoeffler | Building Brand Equity through Corporate Societal Marketing[END_REF] and achieve social legitimacy [START_REF] Morsing | Corporate Social Responsibility as Strategic Auto-Communication: on the Role of External Stakeholders for Member Identification[END_REF]. However, we know little about how consumers actually respond to it.

The effects of CSR and CSR communication on consumers

Most empirical studies put in evidence the strong negative impact of the company's alleged irresponsible acts (e.g., air and water pollution, child labour, human rights violations) on attitude towards the firm [START_REF] Murray | Using a Hierarchy-of-Effects Approach to Gauge the Effectiveness of Corporate Social Responsibility to Generate Goodwill toward the Firm: Financial versus Nonfinancial Impacts[END_REF][START_REF] Folkes | Effects of Information about Firms' Ethical and Unethical Actions on Consumers' Attitudes[END_REF][START_REF] Mohr | Do Consumers Expect Companies to be Socially Responsible. The Impact of Corporate Social Responsibility on Buying Behavior[END_REF], as well as on attitude towards the product and purchase intent [START_REF] Murray | Using a Hierarchy-of-Effects Approach to Gauge the Effectiveness of Corporate Social Responsibility to Generate Goodwill toward the Firm: Financial versus Nonfinancial Impacts[END_REF]Swaen andVanhamme, 2004, 2005). More recently, [START_REF] Mohr | The Effects of Corporate Social Responsibility and Price on Consumer Responses[END_REF] have demonstrated an asymmetrical impact of societal practices on consumers' perceptions, which had already been suggested by [START_REF] Creyer | The Influence of Firm Behavior on Purchase Intention: Do Consumers Really Care about Business Ethics?[END_REF]: good performances in terms of CSR positively influence consumers' attitude towards the firm and purchase intent, but bad performances damage them even more. However, this negative relation may depend on consumers' attributions of blame [START_REF] Klein | Corporate Social Responsibility and Consumers' Attributions and Brand Evaluations in a Product-Harm Crisis[END_REF]. While the negative impact of irresponsible acts is unambiguous, the positive effect of good societal performances is more controversial [START_REF] Brown | The Company and the Product: Corporate Associations and Consumer Product Responses[END_REF][START_REF] Sen | Does Doing Good Always Lead to Doing Better? Consumer Reactions to Corporate Social Responsibility[END_REF][START_REF] Swaen | See how 'Good' we are: The Dangers of Using Corporate Social Activities in Communication Campaigns[END_REF][START_REF] Mohr | The Effects of Corporate Social Responsibility and Price on Consumer Responses[END_REF]. This effect is to be shown in the attitude towards the firm, but not systematically in the attitude towards the product or purchase intent [START_REF] Brown | The Company and the Product: Corporate Associations and Consumer Product Responses[END_REF][START_REF] Swaen | See how 'Good' we are: The Dangers of Using Corporate Social Activities in Communication Campaigns[END_REF]. To add to this body of research on consumers' perceptions of societal practices, academics also study the moderating effects of different variables. Some explore situational moderators such as the firm's perceived involvement [START_REF] Ellen | Charitable Programs and the Retailer: Do they Mix?[END_REF]Becker-Olsen et al., 2006) or perceived company-cause congruency [START_REF] Ellen | Charitable Programs and the Retailer: Do they Mix?[END_REF][START_REF] Sen | Does Doing Good Always Lead to Doing Better? Consumer Reactions to Corporate Social Responsibility[END_REF]Becker-Olsen et al., 2006). Others investigate individual moderators such as consumers' tendency to behave socially [START_REF] Klein | Corporate Social Responsibility and Consumers' Attributions and Brand Evaluations in a Product-Harm Crisis[END_REF][START_REF] Mohr | The Effects of Corporate Social Responsibility and Price on Consumer Responses[END_REF] or consumers' degree of support for the cause [START_REF] Sen | Does Doing Good Always Lead to Doing Better? Consumer Reactions to Corporate Social Responsibility[END_REF][START_REF] Mohr | The Effects of Corporate Social Responsibility and Price on Consumer Responses[END_REF].

If CSR initiatives have already a long history, communicating proactively about them is more recent and dates back to the 90's. That is why the specific effects of proactive CSR communication have received little attention in marketing research so far. [START_REF] Schlegelmilch | The Perils and Opportunities of Communicating Corporate Ethics[END_REF] generally discuss the perils and opportunities of communicating corporate ethics. Other works focus on the effect of previous CSR communication in the case of a crisis [START_REF] Swaen | See how 'Good' we are: The Dangers of Using Corporate Social Activities in Communication Campaigns[END_REF][START_REF] Vanhamme | Too Good to be True! The Effectiveness of CSR History in Countering Negative Publicity[END_REF].

Concerning the specific effects of environmental communication, independently from the CSR body of research aforementioned, several research works have been published in the early 90's, in a specific American context, under the term 'green advertising'. Green advertising is defined as "any ad […] that 1-explicitely or implicitly addresses the relationship between a product or the biophysical environment, 2-promotes a green lifestyle […] or 3-presents a corporate image of environmental responsibility" (Banerjee et al., 1995, p.22). Apart from proposing typologies of environmental claims [START_REF] Carlson | A Content Analysis of Environmental Advertising Claims: A Matrix Method Approach[END_REF][START_REF] Banerjee | Shades of Green: A Multidimensional Analysis of Environmental Advertising[END_REF], they also examine several conditions of claims' efficacy on consumers.

They note that specific and detailed claims are more persuasive than vague and ambiguous ones [START_REF] Kangun | Environmental Advertising Claims: A Preliminary Investigation[END_REF][START_REF] Davis | Good Ethics is Good for Business: Ethical Attributions and Response to Environmental Advertising[END_REF]. [START_REF] Davis | Good Ethics is Good for Business: Ethical Attributions and Response to Environmental Advertising[END_REF] shows that claim emphasis also plays a role: when the environmental attribute is presented as a second attribute behind a more central one, consumers perceive the ad as less manipulative than when the environmental claim is the main one. [START_REF] Obermiller | The Baby is Sick / The Baby is Well: A Test of Environmental Communication Appeal[END_REF] demonstrates the importance of the message formulation: a "sick baby" appeal (i.e., a message emphasizing the severity of the problem) is more efficient than a "well baby" appeal (i.e., a message stressing the significance of individual action), when concern for the environmental problem is high (but less efficient in the opposite case).

Surprisingly, [START_REF] Schuhwerk | Green or Non Green? Does Type of Appeal Matter when Advertising a Green Product?[END_REF] show that for people highly involved with the environment, there is no significant difference of efficacy between a green appeal or a cost-saving appeal, whereas a green appeal is superior for people weakly involved, probably because the first ones are more sceptics towards green claims. Later, in a Chinese context, [START_REF] Chan | The Effectiveness of Environmental Advertising: the Role of Claim Type and the Source Country Green Image[END_REF] demonstrates that the country of origin of the product being advertised also plays a role: the more eco-friendly the country, the more persuasive the ad. More recently, in the UK context, [START_REF] Peattie | Climate Change: A Social and Commercial Marketing Communications Challenge[END_REF] review the challenges private and public sectors face to communicate about climate change and encourage ecological behaviours.

At this stage, numerous questions remain unanswered, specifically in a European context: is CSR communication advisable? which practices should be advertised? towards which target? is credibility important, and if so, does it come from the message itself or from its source [START_REF] Swaen | The Use of Corporate Social Responsibility Arguments in Communication Campaigns: Does Source Credibility Matter?[END_REF]? which media are the best to communicate about societal involvement? Knowledge about CSR communication is clearly still limited. As a first step, the general mechanism of brand equity building through CSR communication (specifically through environmental communication in this paper), discussed at a pure theoretical level [START_REF] Hoeffler | Building Brand Equity through Corporate Societal Marketing[END_REF], should be empirically studied.

Theoretical framework

Focusing on consumers' perceptions, the present research adopts [START_REF] Keller | Conceptualizing, Measuring, and Managing Customer-Based Brand Equity[END_REF][START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF] general customer-based approach, which is the most commonly used in marketing research [START_REF] Czellar | Un Modèle Intégrateur du Capital-Client de la Marque : une Perspective Psycho-Cognitive[END_REF]. Keller (2003, p.60) defines brand equity as "the differential effect that brand knowledge has on consumer response to the marketing of that brand" and measures it through the cognitive antecedents of consumers' brand knowledge. As in Keller's framework, we consider brand knowledge as a composition of brand attention and brand image. Any change in the marketing-mix that affects brand attention or imagecommunication actions or possible alliances with other brands, events, causesinfluence brand knowledge, and therefore brand equity. In this research, we control brand attention and concentrate on the influence of environmental communication on brand equity through its effects on brand image.

According to the associative network theory [START_REF] Bower | Mood and Memory[END_REF][START_REF] Mitchell | Models of Memory: Implications for Measuring Knowledge Structures[END_REF], brand image is composed of all the associations linked to the brand in consumers' minds. These associations mirror the meaning of the brand for consumers. Three dimensions characterise them: their strength, favourability and uniqueness [START_REF] Keller | Conceptualizing, Measuring, and Managing Customer-Based Brand Equity[END_REF][START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF]. Strength qualifies the intensity of the connection between the associations and the brand. Strong associations help speed up the reactivation of information stored in memory. Favourability measures the desirability of the associations. Uniqueness assesses the degree of specificity of the associations to the brand (whether associations are shared with competitors or not). Finally, customer-based brand-equity depends on the strength, the favourability and the uniqueness of brand associations [START_REF] Keller | Conceptualizing, Measuring, and Managing Customer-Based Brand Equity[END_REF][START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF][START_REF] Krishnan | Characteristics of Memory Associations: A Consumer-Based Brand Equity Perspective[END_REF]. In this research, we specifically investigate the impact of environmental communication on the two main dimensions of brand associationsstrength and favourability of associationsand on a more global measure of brand equity.

Effects of environmental communication

At a theoretical level, [START_REF] Hoeffler | Building Brand Equity through Corporate Societal Marketing[END_REF] specifically discuss the impact of CSR on customer-based brand equity. They argue that CSR can enhance brand image by generating new abstract associations, associations to the cause itself, associations related to an idealised brand user, or associations related to brand personality (the brand may appear as more sincere, caring or genuine). When the brand communicates about its CSR initiatives, in particular its environmental initiatives, it draws consumers' attention on environmental associations specifically, therefore reinforcing their strength. Furthermore, as firms fully control the way they communicate about their environmental involvement, they do so in order to convey a positive image of them in line with consumers' expectations. According to a survey conducted in 2008 by IFOP (Le Monde, June 3, 2008), consumers pay more and more attention to firms' societal responsibility when buying and consuming, and evaluate positively those firms that behave with diligence. More theoretically, environmental communication generates other-oriented intrinsic value [START_REF] Holbrook | Customer Value: A Framework for Analysis and Research[END_REF]. It provides different hedonic benefits such as a self-expression benefit [START_REF] Chandon | A Congruency Framework of Sales Promotion Effectiveness[END_REF], as consumers can display their values around them [START_REF] Hoeffler | Building Brand Equity through Corporate Societal Marketing[END_REF], or an experiential benefit, as consumers have the impression to contribute to general well-being.

Therefore, when a brand communicates about its environmental involvement, it reactivates these hedonic and experiential benefits, and reinforces the favourability of brand environmental associations.

Given these two discussions, Hypothesis 1 is: H1: Environmental communication enhances the strength (H1a) and the favourability (H1b) of brand environmental associations, as well as brand equity (H1c).

As noted formerly, associating the brand with another entity or a cause can improve brand knowledge, depending on the transferability of this knowledge from the endorser to the brand [START_REF] Keller | Conceptualizing, Measuring, and Managing Customer-Based Brand Equity[END_REF][START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF]. Claim perceived characteristics may facilitate knowledge transferability and therefore emphasise the effect of environmental communication on brand equity, such as the perceived congruency between the brand and the cause supported, and the perceived credibility of the environmental claim.

Effects of the perceived congruency between the brand and the cause supported

Cause-related communication efficiency depends on key variables such as the congruency of donations (i.e., product rather than cash contributions) with the firm's core business [START_REF] Ellen | Charitable Programs and the Retailer: Do they Mix?[END_REF] or overall brand-cause congruency [START_REF] Hoeffler | Building Brand Equity through Corporate Societal Marketing[END_REF][START_REF] Motion | Equity in Corporate Co-Branding: The Case of Adidas and the All Blacks[END_REF][START_REF] Hamlin | The Impact of Cause Branding on Consumer Reactions to Products: Does Product/Cause 'Fit' Really Matter?[END_REF]Becker-Olsen et al., 2006). Congruency is conceptualised as the degree to which two elements of a pair are perceived as being well assorted [START_REF] Park | Evaluation of Brand Extensions: The Role of Product Feature Similarity and Brand Concept Consistency[END_REF].

In case of high congruency between the brand and the cause supported, consumers infer more associations [START_REF] Hoeffler | Building Brand Equity through Corporate Societal Marketing[END_REF] that are clearer and less ambiguous [START_REF] Erdem | Brand Equity as a Signaling Phenomenon[END_REF] and more likely to match existing cognitive structure (Becker-Olsen et al., 2006).

Hence, higher congruency generates stronger environmental associations. Alternatively, lower congruency generates inferences that are harder to organise within consumer existing brand knowledge, and therefore weaker environmental associations.

Thus, the discussion leads to Hypothesis 2: H2: In case of environmental communication, the perceived congruency between the brand and the cause supported increases the strength of brand environmental associations (H2a), and therefore brand equity (H2b).

Effects of the perceived credibility of the environmental claim

Moreover, environmental communication efficiency depends on the perceived credibility of the environmental claim [START_REF] Erdem | Brand Equity as a Signaling Phenomenon[END_REF]. As an illustration, CSR information coming from a commercial source should be perceived as less credible than the same information coming from an independent organisation [START_REF] Mohr | Do Consumers Expect Companies to be Socially Responsible. The Impact of Corporate Social Responsibility on Buying Behavior[END_REF], or from consumers' organisations [START_REF] Swaen | The Use of Corporate Social Responsibility Arguments in Communication Campaigns: Does Source Credibility Matter?[END_REF]. The perceived credibility of the environmental claim could consequently influence consumers' decision to interpret, encode and stock the message related to societal involvement. On the other hand, non-credible information may prevent the construction of strong associations. The perceived credibility of the environmental claim then appears as a necessary condition to build strong environmental associations.

Therefore, we postulate that: H3: In case of environmental communication, the perceived credibility of the environmental claim increases the strength of brand environmental associations (H3a), and therefore brand equity (H3b).

Methodology

Experiment and stimuli

Testing the conceptual framework implies to compare the relative effect on brand equity of two similar communications, one showing environmental claim, the other not (control group).

Brand and sector.

In both conditions, we first present D'ECO, a fictitious retailer in the furniture and home improvement industry, by showing the respondents a corporate Web site home page (see Appendix 1). We choose a fictitious corporate brand, as in many previous studies [START_REF] Brown | The Company and the Product: Corporate Associations and Consumer Product Responses[END_REF][START_REF] Swaen | The Use of Corporate Social Responsibility Arguments in Communication Campaigns: Does Source Credibility Matter?[END_REF], to avoid any effects of prior brand familiarity (we checked the availability of the brand name and verified respondents were unfamiliar with it: mean = 1.56 on a seven-point scale). The case of a retailer is of particular interest as CSR communication is a very common practise in retail [START_REF] Jones | Corporate Social Responsibility: A Case Study of the Top Ten Global Retailers[END_REF]. Furthermore, for the choice of the product category, we rejected several industries because of their high environmental involvement (e.g., energy), for which ceiling effects might occur, and others that are intrinsically controversial (e.g., automotive, oil and gas), which might boost consumers' suspicion. In contrast, the furniture and home improvement industry is an experience-driven category, which makes brand equity more critical [START_REF] Erdem | Brand Equity as a Signaling Phenomenon[END_REF]. Furthermore, in this sector, many brands (e.g., IKEA) employ a simple brand architecture, in which their corporate brand is the same as their commercial and outlet brands. This characteristic helps remove ambiguity about brand equity inferred by consumers.

To increase task involvement, the experiment indicates that the fictitious company is a real retailer considering a launch in France.

Environmental communication medium.

Previous academic research have used many different media as stimuli for CSR communication: company profile [START_REF] Brown | The Company and the Product: Corporate Associations and Consumer Product Responses[END_REF], radio scripts [START_REF] Ellen | Charitable Programs and the Retailer: Do they Mix?[END_REF], press release [START_REF] Swaen | See how 'Good' we are: The Dangers of Using Corporate Social Activities in Communication Campaigns[END_REF], consumers' associations articles [START_REF] Swaen | The Use of Corporate Social Responsibility Arguments in Communication Campaigns: Does Source Credibility Matter?[END_REF] or newspapers articles (Becker-Olsen et al., 2006). The present research considers the brand Web site (specifically the brand presentation Web page) for four main reasons. First, a Web site is the most frequent medium used to engage in CSR corporate communication [START_REF] Van De Ven | An Ethical Framework for the Marketing of Corporate Social Responsibility[END_REF]; in the United States, 80% of Fortune 500 companies mention their involvement on their Web sites [START_REF] Bhattacharya | Doing Better at Doing Good: When, Why, and How Consumers Respond to Corporate Social Initiatives[END_REF]. Such societal communication generally requires a highly accessible but inexpensive medium to avoid accusations of spending more on communication than on the initiatives themselves (Varadarajan and Menon, 1998;[START_REF] Schlegelmilch | The Perils and Opportunities of Communicating Corporate Ethics[END_REF]. Second, Web sites are a preferred medium to communicate CSR involvement because of the richness of argumentation and opportunities for interactivity they provide [START_REF] Coupland | Corporate Social Responsibility as Argument on the Web[END_REF]. Jones and colleagues (2007) underline its "interactivity, updatability and ability to handle complexity". Third, for product categories such as furniture and home improvement, Web sites are widespread; 47% of French consumers look for information on the Internet before buying furniture in an outlet (Netratings French Panel, 2006). Fourth, brand Web sites can target the best brand clients and influence their attitudes and perceptions of the brand's personality [START_REF] Müller | The Impact of a World Wide Web Site Visit on Brand Image in the Motor Vehicle and Mobile Telephone Industries[END_REF]. We therefore anticipate that online CSR communication influences brand equity after a single exposure, because corporate image generally is malleable compared with corporate reputation and can be modified rapidly through adequate communication [START_REF] Gray | Managing Image and Corporate Reputation[END_REF].

The brand presentation Web page stimulus features four elements: timeline, facts & figures, our vision, and our engagements. In the control group, general press information replaces the fourth block, "our engagements" (see Appendix 2). To ensure realism, we use IKEA's engagements (i.e., producing furniture with wood from certified forests) as inspiration for the environmental claims. Furthermore, engagements regarding raw materials are very common in retailers' CSR communication strategy [START_REF] Jones | Corporate Social Responsibility: A Case Study of the Top Ten Global Retailers[END_REF].

Procedure

The data collection relied on a Web survey, and the experiment consisted of two stages. First, the home page introduced the D'ECO Company and the product categories it sells. Second, respondents read the Web page stimulus (see Appendix 2). Then, they completed the rest of the questionnaire with no possibility of going back to review the Web pages. In the 'environmental communication' condition, only respondents who noticed that D'ECO supported a cause remain in the final data sample.

To access a generalisable sample, we recruited 165 respondents from the online panel of a professional market research institute. Respondents are between 25 and 45 years of age (mean = 33). The sample represents various areas in France and is heterogeneous in terms of gender and socio-economic status. We randomly assigned the subjects to each of the two treatments.

Measures

All constructs use seven-point scales: brand equity, the congruency between the brand and the cause supported, the perceived credibility of the environmental claim, the strength and the favourability of associations, as well as consumers' societal consciousness, an individual characteristic, which is introduced as a covariate. Defined as "the tendency for the consumer to purchase products and services which he/she perceives to have a positive (or less negative) impact on the environment, or to use his/her purchasing power to express current social concerns" [START_REF] Roberts | Profiling Levels of Socially Responsible Consumer Behavior: A Cluster Analytic Approach and its Implications for Marketing[END_REF], consumers' societal consciousness moderates the influence of societal marketing on the firm's evaluation [START_REF] Sen | Does Doing Good Always Lead to Doing Better? Consumer Reactions to Corporate Social Responsibility[END_REF], or on the intention to endeavour a responsible behaviour [START_REF] Mohr | Do Consumers Expect Companies to be Socially Responsible. The Impact of Corporate Social Responsibility on Buying Behavior[END_REF][START_REF] Mohr | The Effects of Corporate Social Responsibility and Price on Consumer Responses[END_REF] in previous research. As conscious consumers specifically support societal initiatives, environmental communication has a stronger personal resonance among them, which justifies considering it as a covariate in our analyses.

To assess consumers' social consciousness and the perceived credibility of the claim, we develop ad hoc scales. For the other measures, we rely on previously validated scales. We conduct checks for unidimensionality and reliability for the multi-items scales and find satisfactory reliability (see Table 1). We use mean item scores to measure the constructs.

Insert Table 1

Consumers' societal consciousness

Three ad hoc items -I try not to buy from companies that strongly pollute.

-When possible, I systematically choose the product that has the lowest negative impact on the environment.

-When I have the choice between two equivalent products, I always wonder which one pollutes less before buying.

Strength of associations

Please indicate the degree of association of each of the following attributes to the brand D'ECO? [START_REF] Keller | Conceptualizing, Measuring, and Managing Customer-Based Brand Equity[END_REF][START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF] -3=very weak / +3=very strong

Favourability of associations

In your opinion, is it positive or negative for the brand D'ECO to have this image? [START_REF] Keller | Conceptualizing, Measuring, and Managing Customer-Based Brand Equity[END_REF][START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF] -3=very negative / +3=very positive

The associations to be assessed come from a qualitative pre-test where 31 consumers were asked to consider the stimuli and to elicit free associations [START_REF] Van Riel | Measuring Corporate Image[END_REF]. In reaction to the environmental engagement, the brand association mostly cited was ecological.

As filler tasks, three other associations were measured for young people, low prices, design.

As a manipulation check, at the end of the questionnaire, we asked the respondents (on a seven-point scale) if the D'ECO Web site was providing information regarding the retailer's environmental involvements. There was a significant difference across the two treatments (means of 6.3 for the 'environmental communication' condition vs. 5.1 for the control group, p < .000), showing the manipulation's success.

Results

Table 2 shows scales' means and standard deviations for each of the experimental treatments. Before testing the hypotheses, to replicate previous findings [START_REF] Keller | Conceptualizing, Measuring, and Managing Customer-Based Brand Equity[END_REF][START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF][START_REF] Krishnan | Characteristics of Memory Associations: A Consumer-Based Brand Equity Perspective[END_REF] in the specific case of environmental associations the authors have checked the influence of the strength and the favourability of the association ecological on customerbased brand equity. A Pearson correlation test reveals a significant and positive correlation between the strength of the association ecological and brand equity (Pearson = 0.5, p < .000), and between the favourability of the association ecological and brand equity (Pearson = 0.4, p < .05). Thus, customer brand-equity increases with the strength and the favourability of the association ecological.

Insert Table 2

Then, H1 is tested with a t-test of the equality of means. Supporting H1a and H1b, the strength (means of 6.1 vs. 5.3, p < .000) and the favourability (means of 6.4 vs. 5.4, p < .000)

of the association ecological are significantly higher when the brand communicates about its environmental initiative than when it does not. Supporting H1c, brand equity is also significantly higher (mean = 4.9) when the brand communicates than when it does not (mean = 4.4 in the control group, p < .05). Thus environmental communication has a significant effect on brand image environmental dimensions, and therefore on brand equity.

A linear regression model is used to test the other hypotheses with the strength of the association ecological and brand equity as successive dependent variables. The perceived congruency between the brand and the cause supported and the perceived credibility of the claim are introduced as independent variables. Societal consciousness is introduced as a covariate. Table 3 summarises the results.

Insert Table 3 Table 3: Surprisingly, consumers' societal consciousness has no significant effect either on the strength of the association ecological or on brand equity.

Discussion

The present research investigates the role of environmental communication in the mechanisms of brand equity building. The experiment exposes subjects to one of two different versions of a brand presentation Web page, showing or not an environmental claim. As postulated, and consistent with the brand equity building principles described by [START_REF] Keller | Conceptualizing, Measuring, and Managing Customer-Based Brand Equity[END_REF], the results validate that environmental communication has a positive impact on the strength and favourability of brand environmental associations, and therefore on brand equity. Furthermore, they show that several situational factors reinforce the effect of environmental communication on brand equity building. This effect increases with the congruency between the brand and the cause supported and with the perceived credibility of the claim, thanks, in both cases, to an increase in the environmental association strength. Tested as a covariate, consumers' societal consciousness seems not to have any influence on brand equity, but this may due to the strong social desirability elicited by the concept, or the fact that there is a strong gap between consumers' declared attitude and effective behaviour, especially in the environmental domain [START_REF] Peattie | Climate Change: A Social and Commercial Marketing Communications Challenge[END_REF]. Further replications should be performed before concluding on that point. On the basis of this work, meaningful implications can be identified.

and credible medium (obtaining a mean score of credibility of 4.8 out of 7), probably more than traditional advertising [START_REF] Banerjee | Shades of Green: A Multidimensional Analysis of Environmental Advertising[END_REF].

From a managerial point of view, the present research has also immediate implications.

Managers now have in hands theoretical arguments to justify their environmental communication practices, not just relying on the fact that many brands use these arguments.

In a general manner, if properly done, environmental communication can contribute to build brand equity by generating or reinforcing environmental image. However, managers have to pay attention to different factors influencing brand equity building. First, to maximise brand equity creation, they will have to ensure that their engagement is congruent with their brand, increasing in turn the transferability of environmental associations to the brand. They will also have to take care of their message credibility. This challenge will become more crucial in the future as observers notice the development of scepticism especially across young people.

Firms should then choose highly credible media to communicate, instead of advertising or mere sponsorship. Communicating on the brand Web site gives the message an institutional dimension, which ensures a certain degree of credibility but a lot more could be investigated in terms of choice of media or about the impact of other communication formats, such as societal reporting, audited publication, codes of conduct or social labelling.

Limitations and future research directions

To conclude, this study presents several limitations and opens routes for future research. If this research proves a general positive effect of environmental communication on brand equity in certain favourable conditions, a lot more need to be investigated to understand the boundary conditions. Initial corporate reputation regarding societal issues, but also the anteriority of the brand's engagement in such societal initiative can moderate the positive impact of environmental communication and should be investigated.

The present research also sheds light on the role of credibility, but does not envisage all sources of credibility. Further research could be done at the message level, at the source level (which brands are legitimate to communicate? is the anteriority of the societal practice important?) but also at the medium level (are there media that are best suited to deliver societal message?). Regarding this last specific point, the research focuses on only one type of communication medium to eliminate this specific source of variance, but future studies will have to generalise results to several media or on the contrary explain different kinds of effects.

New emergent media such as those cited earlier (e.g., societal reporting, audited publication, codes of conduct or social labelling) should be investigated to understand their specific value.

Again these questions should be examined considering the risk of perceptions of "greenwashing". Is there a minimum level of credibility under which brand equity could be damaged? Which factors (initial brand reputation? brand sector? legitimacy to communicate? medium used? executional factors?) may induce perceptions of manipulation and therefore make environmental communication damaging for the brand.

Furthermore, it would be interesting to extend knowledge on environmental communication intermediate effects leading to brand equity reinforcement. Several studies suggest that part of the answer may stem from a greater understanding of how consumers decode the motivations behind CSR communication (Dean, 2004;[START_REF] Pirsch | A Framework for Understanding Corporate Social Responsibility Programs as a Continuum: an Exploratory Study[END_REF][START_REF] Van De Ven | An Ethical Framework for the Marketing of Corporate Social Responsibility[END_REF]. Eventually, considering the attributions of firms' environmental involvement [START_REF] Klein | Corporate Social Responsibility and Consumers' Attributions and Brand Evaluations in a Product-Harm Crisis[END_REF][START_REF] Sjovall | From Actions to Impressions: Cognitive Attribution Theory and the Formation of Corporate Reputation[END_REF] as a mediator between environmental communication and brand equity could also help deepen CSR efficiency understanding. This question is even more crucial in the actual context, because the profusion of CSR claims has prompted a movement that denounces those advertising agencies that encourage "greenwashing" [START_REF] Bradford | Green Wash Confronted: Misleading Advertisement Regulation in the EU and its Member States[END_REF]. If the present research shows that, in a "basic" case, when there is not any clue inducing any intent of "greenwashing", consumers do not necessarily question the claims, and therefore develop a positive attitude towards the brand, we can suppose that perceptions of "greenwashing" or deliberately misleading strategies can damage consumers' attitude toward a brand, and therefore brand equity.

Future research should also replicate the results to other cultural contexts, as societal consciousness seems to vary across them (Maignan and Swaen, 2000). Insisting on this point, [START_REF] Matten | Implicit' and 'Explicit' CSR: A conceptual Framework for Understanding CSR in Europe[END_REF] show that the way European and American envisage CSR initiatives are really different responding to the influence of their national business systems. In the same vein, examining the differences between transitional economies and mature ones could be interesting [START_REF] Grbac | Ethics, Social Responsibility and Business Performance in a Transition Economy[END_REF].

Last but not least, the research should be replicated across different industries, or in a longitudinal perspective as industry maturity regarding CSR involvement, and especially environmental ones probably plays a role, certain engagements becoming prerequisite and no more value adding for the brand. Ceiling effects could therefore appear. Moreover, if all brands in the industry get involved in the same practices, the differentiation power of environmental claims decreases a lot. This assumption raises the question of a possible pioneer effect regarding the cause in which the brand engages.

Conclusion

This research is a first investigation of the effects of CSR communication, and specifically environmental communication on brand equity. Inscribed in Keller's consumer-based framework, it experimentally demonstrates, in the basic setting of a retailer's communication on its Website, the general positive impact of environmental communication on brand equity (through its influence on the strength and uniqueness of brand environmental associations).

Furthermore, it shows the importance of two moderators: the perceived congruency between the brand and the cause supported, and the perceived credibility of the environmental claim. This is a first step only in this research direction, as many other boundary conditions should be investigated regarding the characteristics of the brand (legitimacy, own CSR history...) or of the communication (type of message, medium used...).

Figure 1

 1 Figure 1 represents the entire conceptual framework.

  in the information provided by this Web site -This Web site is fair in what is said and shown 0.92

  p < .001, **p < .01, *p < .05. Both regressions are significant. The results show that the congruency between the brand and the cause supported significantly increases the strength of the association ecological ( = 0.4***) and brand equity ( = 0.3***): H2a and H2b are then supported. The perceived credibility of the claim also significantly increases the strength of the association ecological ( = 0.3**) and brand equity ( = 0.4***): H3a and H3b are then also supported.

Table 1 : Scales

 1

	Variable	Instrument	Reliability (Cronbach's )
	Brand equity	Three items from Yoo and Donthu (2001)	0.91

Table 2 : Descriptive statistics per treatment (on seven-point scales) Societal consciousness Perceived congruency Perceived credibility Environmental association strength Environmental association favourability Brand equity

 2

	Environmental	Mean	4.3	5.7	5.0	6.1	6.4	4.9
	communication (N=115)	Std dev.	1.4	1.0	1.2	1.3	1.0	1.3
	Control Group	Mean	4.2	-	-	5.3	5.4	4.4
	(N=50)	Std dev.	1.4	-	-	1.2	1.4	1.1

Implications

From a theoretical point of view, this research provides an initial piece of evidence of the empirical positive impact of environmental claims on customer-based brand equity.

Surprisingly, this important result has never been empirically demonstrated, specifically on a generalisable sample in Europe, where environmental communication is quickly developing, but research is still scarce. Consistent with the general assumption that an alliance with another entity generates associations' transfers that contribute to modify or reinforce brand equity [START_REF] Keller | Conceptualizing, Measuring, and Managing Customer-Based Brand Equity[END_REF][START_REF] Keller | Strategic Brand Management: Building, Measuring, and Managing Brand Equity[END_REF], the experiment validates that getting involved in an environmental cause and communicating about this engagement to consumers also reinforce brand equity, by modifying brand image [START_REF] Hoeffler | Building Brand Equity through Corporate Societal Marketing[END_REF]. This kind of communication generates or at least reinforces the specific ecological association. As an abstract association, the ecological association should exhibit a better transferability in case of brand extensions [START_REF] Park | Evaluation of Brand Extensions: The Role of Product Feature Similarity and Brand Concept Consistency[END_REF]. Therefore, the integration of the ecological association is a way to enrich brand imagery.

Second, the present research also replicates previous work on the positive effect of the congruency between the brand and the chosen endorser on brand equity building [START_REF] Hoeffler | Building Brand Equity through Corporate Societal Marketing[END_REF][START_REF] Motion | Equity in Corporate Co-Branding: The Case of Adidas and the All Blacks[END_REF]Becker-Olsen and Hill, 2006). Again, we validate that the stronger the congruency the better the transferability of associations. A strong congruency between the brand and the cause supported is probably a boundary condition to create brand differentiation.

Third, the present research confirms previous seminal work [START_REF] Mohr | Do Consumers Expect Companies to be Socially Responsible. The Impact of Corporate Social Responsibility on Buying Behavior[END_REF][START_REF] Swaen | The Use of Corporate Social Responsibility Arguments in Communication Campaigns: Does Source Credibility Matter?[END_REF] on the role of the credibility of societal communication in brand equity building. In the actual context of "greenwashing" mentioned earlier, the perceived credibility of the claim may appear as a pivot variable to explain environmental advertising efficiency.

Furthermore, this research demonstrates that, as supposed, brand Web site can be an accurate


Laurent George

Fabien Lotte

Raquel Viciana Abad

Anatole Lécuyer

Using Scalp Electrical Biosignals to Control an Object by Concentration and Relaxation Tasks: Design and Evaluation

In this paper we explore the use of electrical biosignals measured on scalp and corresponding to mental relaxation and concentration tasks in order to control an object in a video game. To evaluate the requirements of such a system in terms of sensors and signal processing we compare two designs. The first one uses only one scalp electroencephalographic (EEG) electrode and the power in the alpha frequency band. The second one uses sixteen scalp EEG electrodes and machinelearning methods. The role of muscular activity is also evaluated using five electrodes positioned on the face and the neck. Results show that the first design enabled 70% of the participants to successfully control the game, whereas 100% of the participants managed to do it with the second design based on machine learning. Subjective questionnaires confirm these results: users globally felt to have control in both designs, with an increased feeling of control in the second one. Offline analysis of face and neck muscle activity shows that this activity could also be used to distinguish between relaxation and concentration tasks. Results suggest that the combination of muscular and brain activity could improve performance of this kind of system. They also suggest that muscular activity has probably been recorded by EEG electrodes.

I. INTRODUCTION

In recent years, researches have been conducted to use electrical brain activity for interacting with video games and virtual environments [START_REF] Lécuyer | Brain-computer interfaces, virtual reality, and videogames[END_REF]- [START_REF] Blankertz | The Berlin Brain-Computer interface: Nonmedical uses of BCI technology[END_REF]. In this context, researchers have started to explore signals correlated to concentration and relaxation states [START_REF] Hjelm | Brainball -using brain activity for cool competition[END_REF]- [START_REF] Mühl | Bacteria Hunt : Evaluating multi-paradigm BCI interaction[END_REF]. Several electroencephalographic (EEG) markers have indeed been identified as correlated with mental relaxation, task engagement, attention and mental workload. For example, alpha rhythm (8 Hz-12 Hz) is known to be attenuated or blocked by mental activity and attention [START_REF] Niedermeyer | The normal EEG of the waking adult[END_REF]. Other rhythmic activities such as beta and theta rhythms have been investigated to quantify mental relaxation [START_REF] Lin | Quantifying mental relaxation with EEG for use in computer games[END_REF] and attention level [START_REF] Pope | Biocybernetic system evaluates indices of operator engagement in automated task[END_REF]. Hamadicharef et al. [START_REF] Hamadicharef | Learning EEG-based Spectral-Spatial Patterns for Attention Level Measurement[END_REF] have also assessed the level of attention through EEG, but employing machine learning methods to learn the best frequency and spatial filters to use. This approach reveals better classification accuracy than using only alpha, beta and theta bands. More recently Mühl et al. proposed to use alpha activity as a passive Brain Computer Interface (BCI) modality [START_REF] Mühl | Bacteria Hunt : Evaluating multi-paradigm BCI interaction[END_REF]. Alpha activity was used in an implicit way to adapt the game content. Enemies speed was increased when the alpha activity was low (which was expected to be correlated with a low relaxation state). Unfortunately, no significant differences for game experience and for user's alpha power modification were found. Electrical activity has also been L. George, F. Lotte, and A.Lécuyer are with INRIA, France, {laurent.f.george, fabien.lotte, anatole.lecuyer}@inria.fr. R. Viciana Abad is with Department of Telecommunication Engineering, University of Jaén, Spain, rviciana@ujaen.es. used in an explicit way. In the game BrainBall [START_REF] Hjelm | Brainball -using brain activity for cool competition[END_REF] (later adapted into a commercial game called Mindball1 ) players must be relaxed to move a ball away. A ratio between beta and alpha activity measured with forehead electrodes was used to control the ball position. Matel Inc. also proposed the MindFlex games2 in which the player has to concentrate to control physical objects. However, we do not have information about the electrical signal and the signal processing used in these games. Despite these promising first results, there is still a number of important scientific questions about such systems that need to be answered. In particular:

• Quantitative and in depth performance analysis are scarce in the litterature; • Due to a lack of comparative study, the best electrodes (number and placement) and signal processing to be used are still not well known; • There is still a debate about whether such systems are pure EEG systems, independent of Electromyogram (EMG) activity, or if EMG plays an important role [START_REF] Heingartner | Mental block[END_REF]. Thus, in this paper we have conducted a study in which users had to perform mental concentration and relaxation tasks to control an object in a video game, based on EEG recordings, which aims at addressing the aforementioned questions.

The remainder of this paper is organized as follows. In Section II, the application developed and the experimental procedure are described. In Section III, results are presented and discussed. Finally, the main conclusions are summarized in Section IV.

II. METHOD

A. Application

The goal of the game was to control the altitude of a spaceship displayed on the screen. Two kinds of instructions were provided to the user: "Go Up" and "Go Down". When "Go Up" instruction was displayed, the user had to try to make the spaceship go up and stay at a high altitude during 35 s. The opposite behavior was expected for the "Go Down" instruction, by making it go down. The spaceship altitude depended on the user's level of concentration or relaxation as computed by the system (see section II-E). The maximum and minimum altitudes were respectively 1 and -1. A green line that symbolizes the smoke of the spaceship was used to provide visual feedback to the participants. Figure 1 displays a screenshot of the application during typical "Go Down" and "Go Up" phases.

B. Procedure

The experiment was carried out in an office room. Participants sat in front of a 24 ′′ LCD screen device. The distance to the screen was 90 cm. Before the experiment began, all participants were informed about the aim of the study and the relation between the spaceship position and their mental state; and they filled out a consent form. To make the spaceship go up, they were suggested to follow one of the two strategies: "focus your attention on the spaceship altitude" and "imagine sending mental orders to the spaceship such as Go up!". To make the spaceship go down, they were suggested to follow one of the two strategies: "do not focus your attention on the spaceship and its altitude" and "focus your attention on your respiration patterns to relax". Participants were instructed to look at the display screen during both conditions. They were also informed that the recorded signals are sensitive to artifacts (like body movement, teeth clenching), for these reason they should move as little as possible throughout the experiment.

The experiment consisted of two parts (Part A and Part B) corresponding to two setups (a version based on alpha activity and a version based on machine learning methods, respectively). To assess differences between the two setups, the experiment had a within-subjects design. Thus all the participants performed each part of the experiment on a different day, separated by less than a week. To eliminate possible order effects between versions, half of the participants started with the first version (group A did Part A first) and the other half with the second version (group B did Part B first).

Each part of the experiment consisted of six sessions. Each session was divided into three blocks. Each block had two phases: one "Go up" and one "Go Down", starting with a randomized order. Phase duration was 35 s. At the start of each game, the instructions were displayed at the top of the application screen for 5 s ("Go up" or "Go down"). The spaceship was displayed and its altitude was directly mapped to the control signal (see section II-E). The blocks were separated by a break of 10 s, during this time the screen was blanked. Each session was separated by a break of less than 2 min. This time was used to run the machine learning process between sessions (see section II-E).

C. Participants

Ten participants (8 men, 2 women) aged from 22 to 34 (µ = 26.2, σ = 4) took part in the experiment. Subjects were randomly assigned to the two different groups A and B.

D. Electrodes montage

Two sets of electrodes were used to record data throughout the experiment. The first set of electrodes (EEG set) was used to record EEG activity. The purpose of the second set (EMG set) was to record EMG activity on the face and the neck. A Gtec UsbAmp was used to acquire EEG data at a sampling rate of 512 Hz (EEG set). This device enabled to use 16 electrodes according to the 10-20 international system. It was used to record EEG activity related to mental relaxation and concentration tasks. The electrodes used were: Fp1, Fpz, Fp2, F3, Fz, F4, T7, C3, Cz, C4, T8, P3, Pz, P4, O1 and O2. Electrodes Fp1, Fp2, Pz were chosen accordingly to BCI literature [START_REF] Lin | Quantifying mental relaxation with EEG for use in computer games[END_REF], [START_REF] Mühl | Bacteria Hunt : Evaluating multi-paradigm BCI interaction[END_REF]. The remaining 11 electrodes were placed on a grid pattern to cover an important surface of the scalp. A ground electrode (located on the left ear) and a reference electrode (located at AFz position) were also used.

To record electrophysiological activity on the user face and neck a MindMedia NeXus 32b device was used (EMG set). Four electrodes were placed on the face (above and below each eye), and one electrode was placed on the neck. A ground electrode (located on the nose) and a reference electrode (located on the forehead) were also used with this setup. These electrodes were not used for online control of the game but only for offline EMG analysis.

E. Signal Processing

Signal acquisition and online processing were conducted using the open-source software OpenViBE [START_REF] Renard | OpenViBE: An Open-Source Software Platform to Design, Test and Use Brain-Computer Interfaces in Real and Virtual Environments[END_REF]. Offline processing was done using Matlab. Two control signals were used during the online experiment. The first one was computed using only 1 scalp EEG electrode and power in the alpha frequency band (CS1). The second one was acquired from 16 scalp EEG electrodes and processed by applying machine learning methods (CS2).

The first control signal (CS1) corresponds to the opposite of the power of the user's alpha frequency band at Pz location. Indeed alpha activity is known to increase when the user is relaxed [START_REF] Niedermeyer | The normal EEG of the waking adult[END_REF]. As this activity is mainly found in the posterior half of the head [START_REF] Niedermeyer | The normal EEG of the waking adult[END_REF], the electrode was placed on Pz position. This activity was quantified by a band power technique [START_REF] Pfurtscheller | Event-related EEG/MEG synchronization and desynchronization: basic principles[END_REF]. Band power was computed 16 times per second on a moving window of 1 s. The alpha band selection was based on the method of individually adjusted bandwidths (IBFW) proposed by Doppelmayr et al. [START_REF] Doppelmayr | Individual differences in brain dynamics: important implications for the calculation of event-related band power[END_REF]. To determine the individual dominant alpha frequency of each participant, we used a 30 s recording of the EEG data with participants closing their eyes. Then, the spectrum of the signal was computed and the frequency (in 6 Hz-20 Hz) that shows the maximum power was chosen. A fixed width of 4 Hz around this value was then used as the subject's alpha frequency band. A calibration phase with no feedback was used to scale the control signal between -1 and 1. The calibration phase corresponded to a 30 s relaxation task and 30 s concentration task, both without any feedback.

To compute the second control signal (CS2), a technique similar to the one proposed in [START_REF] Hamadicharef | Learning EEG-based Spectral-Spatial Patterns for Attention Level Measurement[END_REF] was used. All EEG signals were passed through a bank of 4 Hz bandwidth filters centered on all the frequencies between 2 Hz and 30 Hz.

A common spatial pattern (CSP) method [START_REF] Blankertz | Optimizing spatial filters for robust EEG single-trial analysis[END_REF] was then used to compute spatial filters for each of them. Maximum relevance feature selection was used to select the five most relevant couples of frequency band and spatial filter [START_REF] Peng | Feature selection based on mutual information criteria of max-dependency, max-relevance, and minredundancy[END_REF]. The linear model that best matched features (computed using the selected band pass filters and spatial filters) and both classes (Up and Down) was then determined using linear regression on the training set. The linear equation, selected band filters, and selected spatial filters were then used online.

The learning process was run between each session using all data recorded during the previous sessions of the day. In part A, CS1 was used during the whole experiment (altitude of the spaceship was mapped to CS1). In part B, CS1 was used for the first session to provide feedback to the user when collecting training data for the subsequent CS2 calibration (machine learning); CS2 was used during all the remaining sessions.

III. RESULTS

A. Subjective questionnaire

After each part of the experiment, participants were asked to fill in a questionnaire. Table I provides the average marks they gave for each question. Results showed that participants felt that they had control over the spaceship in both parts. Indeed, the reported sensation of control (average marks given for question 1 and 2) was on average 4.4 for Part A and 5.17 for Part B on a scale between 1 (never) and 7 (always). During Part A, there was no significant difference between the "Go up" and "Go down" conditions (Wilcoxon paired test p = .95). Concerning part B, there seemed to be a difference between "Go up" and "Go down" condition, but it was not significant (Wilcoxon paired test p = .35). Concerning the influence of the control signal, a significantly better feeling of control was observed in Part B (Wilcoxon paired test p = .02).

Questionnaire results about tiredness seemed to indicate that participants felt the experiment relatively tiring. Part B was reported to be less tiring, although this difference was not statistically significant (Wilcoxon paired test p = .20). Participants were also asked to report when they started to feel fatigue during the experiment. Fatigue seems to start after the middle of the experiments (54 % completed for Part A, and 62 % completed for Part B). In the middle of the experiment, participants have already completed 9 min of active control ("Go up" and "Go down").

Concerning the fun, it seems that participants felt an average enjoyment during the game. This could be due to the simplicity of the interface and the absence of rewards during the game. No significant difference was found between the two parts (Wilcoxon paired test p = .28).

B. Online Performances

The first 5 s of each phase were ignored for the analysis of the online performances (it corresponded to the instruction reading time). We assessed performances by computing the average difference between the altitude in the two conditions ("Go up", "Go down") over each block. Indeed, a higher altitude in the "Go up" condition could be interpreted as a success. The online performance indexes are provided in Table II. Spearmann correlation test between performance index and participant's control marks indicates that the difference between conditions seems to be correlated to reported marks (Part A r = .56, p = .09; Part B r = .72, p = .02).

The computation of a Student t-test, between conditions "Go up" and "Go down" in each block shows that there is a significant difference between the two conditions for seven out of the ten participants with CS1 (Part A), and for all the participants with CS2 (Part B) (asterisks in Table II). When the difference is significant it is also always positive: the spaceship altitude in the "Go up" condition is higher than during the "Go Down" condition. Regarding to the influence of the control signal it appears that the use of CS2 with 16 EEG electrodes provided better overall performances compared to CS1 (Wilcoxon paired test p = .002). It highlights the need of machine learning and subject specific design and confirms results in [START_REF] Hamadicharef | Learning EEG-based Spectral-Spatial Patterns for Attention Level Measurement[END_REF]. The first column corresponds to the use of alpha band power with electrode Pz (CS1). The second column corresponds to the use of machine-learning methods with 16 EEG electrodes (CS2). Offline performances using EMG set are presented in column 3. Offline performances using the combination of EEG and EMG sets are provided in column 4. Last line provides the average altitude difference over participants. Values are presented as mean (std); asterisks represent the significance of the difference ( * : significant at p < .05; * * : significant at p < .01; * * * : significant at p < .001) Fig. 2. Mean altitude of the spaceship on screen as function of different conditions ("Go-Up" vs. "Down" and CS1 vs. CS2). Altitude was averaged over all blocks and all participants. Dotted line represents altitude when alpha frequency band at Pz electrode was used (CS1). Solid line represents altitude when machine-learning method was used with 16 electrodes (CS2).

The analysis of performances evolution over time is shown in Figure 2. It provides the average evolution of altitude for both conditions and both control signals. We observed an increase of performance over the course phase duration with CS2. This suggests that users need time to get into the task.

C. Role of EMG

Co-occurrence of muscular activity is known to result in contamination of EEG by Electromyogram (EMG) [START_REF] Goncharova | EMG contamination of EEG: spectral and topographical characteristics[END_REF]. Therefore an evaluation of EMG activity during the interaction is necessary. For this purpose signals recorded during Part B using face and electrodes (EMG set) were analyzed. We computed a control signal (CS3) based on EMG set employing the same machine learning methods as the one used for CS2 (see section II-E). The usage of EMG set led to a significant difference between the "Go Up" and "Go Down" conditions for all the participants (Table II). This means that the recorded information in facial and neck electrodes can be used to discriminate between the two conditions although the use of EEG set (CS2) provided better performances (Wilcoxon paired test p = .033). One interpretation of these results is that EMG set measured some EEG activity, which is enough to discriminate between tasks (indeed electrodes above the eyes are able to measure some frontal EEG activity). A more likely interpretation is that EMG set measured EMG activity, which provides information to discriminate between tasks. This would mean that a discriminant muscular activity occurred when users try to do the two mental tasks, however they were asked to try to avoid muscular activity during the experiment. This second interpretation would also imply that the EEG set measured a part of this discriminant muscular activity.

To evaluate the combination of EEG and EMG sets in terms of performance the computation of a control signal (CS4) based on the three most relevant EEG features and the two most relevant EMG features was done (to have 5 features as with EEG or EMG alone). The combination of EMG and EEG allowed to increase performances in terms of difference between conditions compared to CS2 (Wilcoxon paired test p = .019). This result may indicate that there are relevant information in the two sets of electrodes that are not redundant between the sets. Future work should be done to quantify the part of information in each set and to qualify the origin of this information (muscular versus brain activity).

IV. CONCLUSION

In this paper, we have explored the use of two different setups based on scalp electrical biosignals corresponding to mental relaxation and concentration tasks to control a video game. Results of this experiment are surprisingly good and suggest that both setups seem well suited for interaction with simple video games. Analysis of signal from face and neck electrodes (EMG set) suggests also that there is relevant information in muscular activity correlated to the two different tasks and that the combination of EEG and EMG electrodes in a hybrid BCI [START_REF] Pfurtscheller | The Hybrid BCI[END_REF] paradigm could improve performance. They also suggest that the current BCI approaches using EEG to detect concentration and relaxation tasks (e.g. [START_REF] Hjelm | Brainball -using brain activity for cool competition[END_REF]) may not be pure BCI as they may be involuntarily using EMG signals recorded with EEG electrodes.

Fig. 1 .

 1 Fig. 1. The video game application with feedback during the two different phases (Go Down on the left, Go Up on the right).

TABLE I QUESTIONNAIRE

 I MARKS REPORTED (MEAN±STD).

	Question	Part A (CS1)	Part B (CS2)
	Did you feel in control of the	4.4 ± 1.51	4.9 ± 1.29
	spaceship during "Go Up"?
	(1: never, 7: always)
	Did you feel in control of the	4.4 ± 1.07	5.45 ± 1.26
	spaceship during "Go Down"?
	(1: never, 7: always)
	Did you feel fatigue related to the	4.3 ± 1.25	4.9 ± 1.20
	interaction? (1: very, 7: not at all)
	How fun was the game?	3.8 ± 1.67	4.2 ± 1.48
	(1: boring, 7: enjoying)
	The first column corresponds to the use of alpha band power technique with
	one electrode Pz (CS1) during part A. The second column corresponds to
	the use of 16 electrodes and machine-learning method (CS2) during part B.

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ACKNOWLEDGMENTS

This work was supported by the French National Research Agency within the OpenViBE2 project and grant ANR-09-CORD-017.