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Ergonomics Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/terg20
Is red the colour of danger? Testing an implicit red–danger association a
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Karyn Pravossoudovitch , Francois Cury , Steve G. Young & Andrew J. Elliot a
Aix-Marseille Université, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France
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Université du Sud Toulon Var, La Garde, France
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School of Psychology, Fairleigh Dickinson University, Teaneck, 07666 NJ, USA
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Department of Clinical and Social Science in Psychology, University of Rochester, 488 Meliora Hall, Rochester, NY 14620, USA Published online: 04 Mar 2014.
To cite this article: Karyn Pravossoudovitch, Francois Cury, Steve G. Young & Andrew J. Elliot (2014) Is red the colour of danger? Testing an implicit red–danger association, Ergonomics, 57:4, 503-510, DOI: 10.1080/00140139.2014.889220 To link to this article: http://dx.doi.org/10.1080/00140139.2014.889220
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Ergonomics, 2014 Vol. 57, No. 4, 503–510, http://dx.doi.org/10.1080/00140139.2014.889220
Is red the colour of danger? Testing an implicit red– danger association Karyn Pravossoudovitcha, Francois Curya,b, Steve G. Youngc and Andrew J. Elliotd* b
a Aix-Marseille Universite´, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France; Universite´ du Sud Toulon Var, La Garde, France; cSchool of Psychology, Fairleigh Dickinson University, Teaneck, 07666 NJ, USA; d Department of Clinical and Social Science in Psychology, University of Rochester, 488 Meliora Hall, Rochester, NY 14620, USA
(Received 13 August 2013; accepted 18 January 2014)
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Research using participant’s self-reports has documented a link between red and danger. In this research, we used two different variants of a Stroop word evaluation task to test for the possibility of an implicit red– danger association using carefully controlled colour stimuli (equated on lightness and chroma). Experiment 1, using words as stimuli, yielded strong evidence of a link between red and danger, and weaker evidence of a green – safety association. Experiment 2, using symbols as stimuli, again yielded strong evidence of a link between red and danger; no green effects were observed. The findings were discussed in terms of the power and promise of red in signal communication. Practitioner Summary: This research documents an implicit association between red and danger. Our findings confirm the wisdom of using red to communicate danger in systematic signal systems, and suggest that red may be used more broadly in other communication contexts to efficiently convey danger-relevant information. Keywords: red; danger; implicit association; signal communication; green
1. Introduction Colour is ubiquitous in our perceptual world. The various colours we perceive not only have aesthetic value (varying in appeal and preference), but also have communication value, carrying different associations and meanings (Elliot and Maier 2012; Goethe [1810]1967; Hill and Barton 2005). In this research, we focus on the communication value of the colour red, specifically the possibility of an implicit link between red and danger. In daily life, red is commonly used to convey danger or danger-relevant concepts. Red is the prototypic colour of alarms, sirens, stop signals and warning signs that convey danger and the need for vigilant attention. This red – danger link is codified in the safety, security and warning systems of a number of different organisations (e.g. American National Standards Institute, U.S. Homeland Security, International Organization for Standardization, Ministe`re de l’Equipement et du Logement, Union Europe´enne; Mayhorn, Wogalter, and Shaver 2004; Miller and Parent, 2006). Red is used in language to refer to problematic or dangerous things or situations to avoid (e.g. ‘red flag’, ‘red herring’, ‘in the red’, ‘code red’ and ‘red handed’). Thus, an implicit red – danger association may form over time and repeated exposure through a process of societal conditioning. It is possible that the aforementioned societal uses of red may themselves be an extension of natural learning. Red is the colour of objectively dangerous things that people encounter in the environment, such as an angry face, exposed blood and fire (Changizi 2009), and even minimal exposure to such critical, survival-relevant stimuli could forge an implicit red – danger association. Furthermore, it is possible that the societal uses of red are an extension of basic physiological processes. In many non-human animals, including several species of ape, red on a conspecific is interpreted as a threat cue, signalling the dominance and/or attack-readiness of an opponent (Pryke 2009; Setchell and Jean Wickings 2005); humans may likewise possess a biologically engrained predisposition to associate red with danger. Thus, both learning-based and biological considerations suggest that red may be linked to danger in a deep, implicit fashion. The existing research on the link between red and danger has primarily been conducted in ergonomics, and has focused exclusively on participant’s self-reports. This research typically involves displaying ‘signal’ words such as Danger, Caution or Attention, on different coloured backgrounds, and having participants rate their perception of the degree of hazard or risk being communicated. It is the red – danger combination that receives the highest hazard and risk ratings in these studies (Borade, Bansod, and Gandhewar 2008; Braun and Silver 1995; Chapanis 1994; Griffith and Leonard 1997; Leonard 1999; Wogalter et al. 1998). Research has yet to be conducted on the red –danger link using methods designed to assess implicit associations. Nevertheless, a few related studies have appeared in the literature and may be noted herein. Moller, Elliot, and Maier (2009)
*Corresponding author. Email: [email protected] q 2014 Taylor & Francis
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used a variant of the Stroop word evaluation task to document that red facilitates responses to negatively valenced words, particularly failure, and inhibits responses to positively valenced words, particularly success (see also Mehta and Zhu 2009; Piotrowski and Armstrong 2012). Fetterman, Robinson, and Meier (2012) used a similar paradigm to establish an implicit association between red and anger. Soriano and Valenzuela (2009) used a version of the Implicit Association Test to demonstrate a link between red and potency. In this research, we used variants of the Stroop word evaluation task to test whether the colour red facilitates responses to danger words (Experiment 1) and danger symbols (Experiment 2). Based on response competition logic (Klinger, Burton, and Pitts 2000), we reasoned that if red is associated with danger, then the simultaneous presentation of red and danger words (e.g. poison) or danger symbols (e.g. a skull and crossbones) should facilitate categorisation relative to other combinations of colours and words/symbols. We used green and grey as control colours. Green is an optimal chromatic contrast to red, because red and green are opposing colours in well-established colour models, and green can take on the opposite meaning of danger, namely safety (as well as peace, calmness and hope; Chan and Courtney 2001; Clarke and Costall 2008; Kaya and Epps 2004). Grey is an optimal achromatic contrast to red, because grey can be matched to chromatic colours on lightness. The extant literature on red and danger is not only limited in relying exclusively on participant’s self-reports, but it is also limited in that none of the existing research has systematically controlled for the lightness and chroma of the colour stimuli when examining hue. This is important, because it makes prior research difficult to interpret due to inevitable confounds between the three colour properties (see Valdez and Mehrabian 1994; Whitfield and Wiltshire 1990). For example, prototypic red is relatively low in lightness and high in chroma, so it is possible that the purported red –danger associations observed in the prior work using prototypic colour stimuli actually represent lightness or chroma effects (i.e. a lightness –danger or chroma – danger association, rather than a hue – danger association). If so, testing for hue –danger associations with red and other hues equated on lightness and chroma would yield null results. In both of the present experiments, red and green were equated on lightness and chroma, and red, green and grey were equated on lightness (grey has no chroma), thereby affording a clear, unconfounded test of the red (hue) –danger association. 2.
Experiment 1
In Experiment 1, danger words and safety words were presented in red, green and grey, and participants categorised them as danger related or safety related. Of foremost interest was whether danger words in red would be categorised most quickly. Facilitation for the green – safety combination and inhibition for the red – safety combination were also examined; grey was thought to have no relevant colour associations and, therefore, was used to anchor any red or green effects. 2.1
Method
2.1.1 Participants and process Thirty (17 female) undergraduates (mean age ¼ 24.2 years) participated. All were native French speakers, had no languagerelated disabilities and were not red – green colour deficient (as indicated by self-report after the experiment). In this and the subsequent study, we report all data exclusions, all manipulations and all measures; sample sizes were set a priori at 30 participants, based on a target of 0.80 power with medium effects sizes (at minimum) anticipated. 2.1.2 Stimuli and pilot test Ten adjectives were used as lexical stimuli (see the Appendix for an English translation of the original French), five denoting danger (disease, peril, poison, emergency and threat) and five denoting safety (quilt, shelter, family, home and refuge). The danger and safety words did not differ in word length (M ¼ 6.2 for each). The words were rated by 64 (44 female) pilot participants for the degree to which they were danger related and safety related (1, not at all; 6, extremely). The danger words were rated as more danger related (M ¼ 5.28, SD ¼ 0.47) than the safety words (M ¼ 1.72, SD ¼ 0.38), t ¼ 38.56, p , 0.001; the safety words were rated as more safety related (M ¼ 4.60, SD ¼ 0.54) than the danger words (M ¼ 1.80, SD ¼ 0.48), t ¼ 28.20, p , 0.001. 2.1.3
Design and procedure
The experiment had a 2 (word type: danger vs. safety) £ 3 (colour: red vs. green vs. grey) repeated measures design. It consisted of 180 trials divided into three blocks. Within a block, each danger and safety word was presented twice in each colour (for a total of six presentations of each word) in random order on a white computer screen. A GretagMacbeth (X-Rite) Eye-One Pro spectrophotometer (Munich, Germany) was used with a trial-and-error procedure (see Elliot and
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Maier 2014) to select colours equated on lightness and chroma at the spectral level (red: LCh[64.9/76.3/32.5], green: LCh [65.5/75.6/145.6], grey: LCh[65.2/ – /297.1]); equated means functionally equivalent (within 2.0 units). Participants’ task was to press a labelled key to indicate whether the word was danger related or safety related. The label position was counterbalanced across participants. For each trial, a fixation circle appeared for 500 ms, then a word appeared until a response was made or 5000 ms elapsed. The inter-trial interval was 1000 ms. Inaccurate (4.96%) responses (Kaze´n and Kuhl 2005) were omitted a priori. Thirty practice trials with the danger-related and safety-related words preceded the experiment.
Preliminary analyses in this and the subsequent experiment treating participant sex as a factor found no main effects, nor did sex moderate the theoretically central interaction; as such, sex was not considered further. Participants’ reaction times to categorise the words were submitted to a 2 (word type) £ 3 (colour) repeated measures ANOVA. The analysis revealed a significant main effect of word type, F(1, 29) ¼ 12.89, p ¼ 0.001, h2p ¼ 0:31, indicating that participants were faster in categorising safety words (M ¼ 643.64 ms, SD ¼ 91.77) than danger words (M ¼ 671.55 ms, SD ¼ 104.99). The main effect of colour was not significant, F(2, 58) ¼ 1.87, p ¼ 0.16. More importantly, a significant word type £ colour interaction, F(2, 58) ¼ 25.97, p , 0.001, h2p ¼ 0:47, indicated that participants were faster in categorising danger words presented in red (M ¼ 642.85 ms, SD ¼ 103.98) versus green (M ¼ 693.93 ms, SD ¼ 111.21), t(29) ¼ 4.86, p , 0.001, or grey (M ¼ 677.87 ms, SD ¼ 111.99), t(29) ¼ 4.73, p , 0.001 (see Figure 1). Although not significant, there was a trend for danger words presented in green to be categorised more slowly than danger words presented in grey, t(29) ¼ 1.75, p ¼ 0.09. For safety words, a different pattern emerged. Participants were slower in categorising words presented in red (M ¼ 657.64 ms, SD ¼ 97.77) than in green (M ¼ 627.10 ms, SD ¼ 87.99), t(29) ¼ 3.64, p , 0.001, but comparing safety words presented in red versus grey (M ¼ 646.19 ms, SD ¼ 99.45) revealed no significant difference, t(29) ¼ 1.46, p ¼ 0.15. The categorisation times for safety words presented in green and grey significantly differed, t(29) ¼ 2.82, p ¼ 0.008. In sum, the results indicated that red was positively associated with danger, as threat words were categorised more quickly in red than in green and grey. In addition, green was shown to be positively associated with security, as comfort words were categorised more quickly in green than in red and grey. 2.2.2
Ancillary analyses: errors
Although errors were infrequent, we conducted ancillary analyses to explore whether participants made systematic errors when categorising the words. A 2 (word type) £ 3 (colour) repeated measures ANOVA on errors revealed a significant main effect of word type, F(1, 29) ¼ 8.21, p ¼ 0.008, h2p ¼ 0:22, indicating that participants made more mistakes in categorising safety words (M ¼ 5.27, SD ¼ 4.83) than danger words (M ¼ 3.67, SD ¼ 4.34). The main effect of Colour was not significant, F(2, 58) ¼ 0.78, p ¼ 0.46. More importantly, a significant word type £ colour interaction, F(2, 800 750 Reaction time
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2.2 Results and discussion 2.2.1 Primary analyses: reaction times
Red
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700 650 600 550 500 SAFETY
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Figure 1. (Colour online) Mean response latencies for danger and safety words presented in red, green and grey. The pattern of means for each danger word and each safety word was the same as the aggregate pattern with one exception: Participants were not slower to categorise the word family in red versus grey.
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58) ¼ 13.10, p , 0.001, h2p ¼ 0:31, indicated that participants made more mistakes when danger words were presented in green (M ¼ 1.83, SD ¼ 2.28), t(29) ¼ 3.67, p ¼ 0.001, and grey (M ¼ 1.20, SD ¼ 1.58), t(29) ¼ 2.29, p ¼ 0.03 than in red (M ¼ 0.63, SD ¼ 1.22). There was a non-significant trend for participants to make more errors for danger words presented in green than in grey, t(29) ¼ 1.82, p ¼ 0.08. When examining responses to safety words, participants made more mistakes when the words were presented in red (M ¼ 2.63, SD ¼ 2.51) versus green (M ¼ 1.10, SD ¼ 2.04), t(29) ¼ 4.10, p , 0.001 or in grey (M ¼ 1.53, SD ¼ 1.25), t(29) ¼ 2.58, p ¼ 0.02. There was no difference between safety words presented in green versus grey, t(29) ¼ 1.35, p ¼ 0.19. These results supplement the primary findings for reaction time, showing that participants made errors in a systematic manner consistent with the notion that red conveys danger relative to green and grey. With regard to errors on safety words, the pattern is somewhat different from that obtained in the primary analyses; here there is evidence for red – safety inhibition, rather than green– safety facilitation.
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3.
Experiment 2
Experiment 2 sought to replicate Experiment 1 using symbols rather than words. Danger and non-danger symbols were presented surrounded by red, green or grey, and participants’ task was to categorise them as danger related or non-danger related; non-danger related rather than safety related was used as the categorisation choice because standardised safety symbols are not available in international classifications. In addition, this design feature facilitates clarity of interpretation in that any observed effect must be due to danger (not safety). 3.1
Method
3.1.1 Participants Thirty (15 female) undergraduates (mean age ¼ 24.8 years) participated. They were native French speakers, had no language-related disabilities and were not red – green colour-blind. 3.1.2
Stimuli and pilot test
Ten symbols were used as stimuli (see the Appendix), five denoting danger (from Union Europe´enne) and five denoting non-danger (from Ministe`re de l’Equipement et du Logement). The symbols were rated by 65 (41 female) pilot participants for the degree to which they were danger related (1, not at all; 6, extremely). The danger symbols were rated as more danger related (M ¼ 5.43, SD ¼ 0.93) than were the non-danger symbols (M ¼ 1.28, SD ¼ 0.71), t ¼ 63.33, p , 0.001. 3.1.3 Design and procedure The experiment had a 2 (symbol type: danger vs. non-danger) £ 3 (colour: red vs. green vs. grey) repeated measures design. It consisted of 180 trials divided into three blocks. Within a block, each danger and non-danger symbol was presented six times (twice surrounded by each colour) in random order on a white computer screen. The same colour values as used in Experiment 1 were used in this experiment. Participants’ task was to press a labelled key to indicate whether the symbol was danger related or non-danger related. The label position was counterbalanced across participants. For each trial, a fixation circle appeared for 500 ms, then a symbol appeared until a response was made or 5000 ms elapsed. The inter-trial interval was 1000 ms. Inaccurate (2.94%) responses were omitted a priori. Thirty practice trials with the danger-related and non-danger-related symbols preceded the experiment. 3.2
Results and discussion
3.2.1 Primary analyses: reaction times Participants’ reaction times to categorise the symbols were submitted to a 2 (symbol type) £ 3 (colour) repeated measures ANOVA. The analysis revealed a significant main effect of symbol type, F(1, 29) ¼ 5.33, p ¼ 0.028, h2p ¼ 0:16, indicating that participants were faster in categorising danger symbols (M ¼ 529.72 ms, SD ¼ 55.39) than non-danger symbols (M ¼ 541.66, SD ¼ 11.54). The main effect of colour was not significant, F(2, 58) ¼ 0.41, p ¼ 0.67. More importantly, a significant symbol type £ colour interaction, F(2, 58) ¼ 22.54, p , 0.001, h2p ¼ 0:44, indicated that participants were faster in categorising danger symbols surrounded by red (M ¼ 517.40 ms, SD ¼ 55.17) versus green (M ¼ 538.22 ms, SD ¼ 60.22), t(29) ¼ 4.51, p , 0.001, or grey (M ¼ 533.53 ms, SD ¼ 56.10), t(29) ¼ 3.58, p ¼ 0.001 (see Figure 2). There was no difference between danger symbols surrounded by green versus grey, t(29) ¼ 1.22, p ¼ 0.23.
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540 520 500 480 460 440 420 400
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DANGER
NON-DANGER Symbol type
Figure 2. (Colour online) Mean response latencies for danger and non-danger symbols surrounded by red, green and grey. The pattern of means for each danger symbol and each safety symbol was the same as the aggregate pattern.
For non-danger symbols, participants were slower when the symbols were surrounded by red (M ¼ 557.41 ms, SD ¼ 63.57) versus green (M ¼ 530.06 ms, SD ¼ 64.27), t(29) ¼ 5.12, p , 0.001, or grey (M ¼ 537.51 ms, SD ¼ 69.60), t(29) ¼ 3.14, p ¼ 0.004. Unlike Experiment 1, there was no difference between non-danger symbols surrounded by green versus grey t(29) ¼ 1.41, p ¼ 0.17; this is likely due to the control stimuli being neutral, rather than positive in valence (as in Experiment 1). In sum, the results indicated that red was positively associated with danger, as danger-related symbols were categorised faster on red than on green or grey backgrounds. Furthermore, reaction times to non-danger symbols were inhibited when they were presented on a red background compared with both on a green or grey background. This experiment did not yield any green effects, most likely due to the use of neutral, rather than safety-related target stimuli. 3.2.2 Ancillary analyses: errors As in Experiment 1, we conducted ancillary analyses to test whether participants’ errors were systematically influenced by colour. A 2 (symbol type) £ 3 (colour) repeated measures ANOVA on errors revealed a significant main effect of colour, F(2, 58) ¼ 5.59, p ¼ 0.006, h2p ¼ 0:16, indicating that participants made more mistakes when the symbol was presented surrounded by red (M ¼ 2.27, SD ¼ 2.24) versus green (M ¼ 1.63, SD ¼ 1.61) or grey (M ¼ 1.40, SD ¼ 1.48). The main effect for symbol type was not significant, F(1, 29) ¼ 0.004, p ¼ 0.95. More importantly, a significant symbol type £ colour interaction, F(2, 58) ¼ 6.59, p ¼ 0.003, h2p ¼ 0:19, was revealed. Colour had no impact on participants’ errors for danger-related words (all ps . 0.13). However, colour did influence categorisation accuracy for non-danger words; specifically, participants made more mistakes when non-danger symbols were surrounded by red (M ¼ 1.57, SD ¼ 2.01) versus green (M ¼ 0.57, SD ¼ 0.90), t(29) ¼ 3.26, p ¼ 0.003, or grey (M ¼ 0.50, SD ¼ 0.90), t(29) ¼ 3.44, p ¼ 0.002. There was no difference between non-danger symbols surrounded by green versus grey, t(29) ¼ 0.35, p ¼ 0.73. These results supplement the primary findings for reaction time. Participants were most likely to mistakenly categorise a non-danger symbol as danger related when it was presented on a red, relative to green or grey, background. 4. General discussion The results from our two experiments provided strong evidence of a red –danger association. Red was linked to danger across two different types of stimuli – lexical and pictorial – and across two different types of dependent measures – reaction times and number of errors. A green –safety association was observed in Experiment 1, although this was only supported by reaction time data, not error data. These findings for red are consistent with those observed in the ergonomics literature by a number of researchers (e.g. Chapanis 1994; Leonard 1999; Wogalter et al. 1998). However, the prior work focused exclusively on self-reported associations between red and danger-relevant concepts, whereas this research used a modified Stroop procedure to document the red – danger association implicitly. Another important contribution of the present, relative to the prior, work is that our findings were obtained using hue stimuli systematically equated for lightness and chroma at the spectral level.
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By rigorously controlling for lightness and chroma, this research was able to rule out, for the first time, alternative explanations based on lightness –danger and chroma – danger associations. This methodological improvement led to a clear, unconfounded demonstration of a red – danger association, but also left open the question of which type of red is most strongly connected to the concept of danger. In future work it would be helpful to conduct an additional series of experiments in which the red hue is held constant while lightness and chroma are systematically varied in different ways, in order to determine the precise variant of red that conveys danger most clearly and quickly. Our findings add to a growing stream of evidence converging across multiple literature (e.g. the psychological literature, the anthropological literature, the non-human primate literature; Elliot and Maier 2012; Hill and Barton 2005; Setchell and Jean Wickings 2005), pointing to the signal value of red. Although we think it likely that the red – danger link observed herein has roots in biology, as well as learning processes (see Changizi 2009; Elliot and Maier 2014), it is important to highlight that our research was not designed to test this assumption. It is possible that the popular use of red to convey danger-relevant concepts initially emerged randomly, and only became deeply embedded (i.e. implicit) over time through conditioning processes. Future research is needed to begin to examine the ultimate source of the implicit red –danger link, perhaps by conducting cross-cultural investigations, or by creating novel colour –danger associations in the laboratory and comparing and contrasting their properties with the focal red –danger association. Future work would also do well to examine other implicit associations to red that might be derived from the non-human primate literature as well, such as red and sexual receptivity (Gue´guen 2012; Pazda, Elliot, and Greitemeyer 2012). In our experiments, participants made categorisations based on the focal stimulus feature, danger, not hue, which was an (ostensibly) irrelevant stimulus feature. Nevertheless, hue produced effects, suggesting not only that hue was processed in obligatory fashion, but also that the meaning linked to hue was likely activated implicitly. This is impressive evidence in support of the implicit nature of the observed association (Meier, Robinson, and Clore 2004; Moller, Elliot, and Maier 2009), but additional evidence using other, conceptually related, methodologies (e.g. a lexical decision task, an implicit association task) could also be sought to further bolster the case. Most impressive of all would be to test the automaticity of the red –danger association using non-conscious colour priming procedures, such as those utilised in research by Schmidt (2000). Experiment 1 yielded tentative evidence for an implicit green –safety association, which is consistent with some research on self-reported colour –meaning associations (Chan and Courtney 2001). Green is beginning to get more attention in the colour literature, as researchers are starting to consider the possibility that green may also, at times, serve as an implicit cue that exerts a subtle influence on affect cognition, and behaviour (Akers et al. 2012; Lichtenfeld et al. 2012; Schuldt in press). However, we suspect that the power, breadth and applicability of green’s meaning and influence will be far less than that of red. Many aspects of biology, culture and language point to red as a colour of particular poignancy and prominence (see Elliot and Maier 2014). The real-world implications of our findings are straightforward, particularly with regard to signal communication. Many systematic signal systems use red to communicate danger-relevant information, and regardless of the ultimate source of the red – danger link, our data confirm the wisdom of using red for this purpose. Dangerous situations sometimes require quick, efficient responding, and red seems to be the optimal colour to facilitate such responding. As noted earlier, future research is needed to determine what precise variant of red (in terms of lightness and chroma) best facilitates responding; this would then be the colour of choice for use in brake lights, traffic lights and related signals using red coloration (see Changizi et al. 2014, for additional, related ideas for future research and application). Red may be useful as a danger cue in other communication contexts beyond formal signage or signal systems. Researchers are beginning to explore such possibilities, and are finding, for example, that a red background coupled with a loss-framed message is particularly persuasive in vaccination appeals (Chien 2011, 2013; Gerend and Sias 2009). The communication value of red has been recognised for centuries (Gamst 1975; Goethe [1810]1967), but we also think the breadth of applicability of this value has been under-appreciated. We believe that this is changing, as researchers begin to empirically document the presence and potential utility of colour – meaning associations. References Akers, A., J. Barton, R. Cossey, P. Gainsford, M. Griffin, and D. Micklewright. 2012. “Visual Color Perception in Green Exercise: Positive Effects on Mood and Perceived Exertion.” Environmental Science and Technology 46: 8661– 8666. Borade, A. B., S. V. Bansod, and V. R. 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Chan, A. H. S., and A. J. Courtney. 2001. “Color Associations for Hong Kong Chinese.” International Journal of Industrial Ergonomics 28: 165– 170. Changizi, M. 2009. The Vision Revolution: How The Latest Research Overturns Everything We Thought We Knew About Human Vision. Dallas: Benbella Books. Changizi, M., M. Brucksch, R. Kotecha, K. McDonald, and K. Rio. 2014. “Ecological Warnings.” Safety Science 61: 36 – 42. Chapanis, A. 1994. “Hazards Associated with Three Signal Words and Four Colours on Warning Signs.” Ergonomics 37: 265– 275. Chien, Y. 2011. “Use of Message Framing and Color in Vaccine Information to Increase Willingness to be Vaccinated.” Social Behavior and Personality: An International Journal 39: 1063– 1072. Chien, Y. 2013. “Persuasiveness of Online Flu-Vaccination Promotional Banners.” Psychological Reports 112: 365–374. Clarke, T., and A. Costall. 2008. “The Emotional Connotations of Color: A Qualitative Investigation.” Color Research and Application 33: 406– 410. Elliot, A. J., and M. A. Maier. 2012. “Color-in-Context Theory.” Advances in Experimental Social Psychology 45: 63 – 125. Elliot, A. J., and M. A. Maier. 2014. “Color Psychology: Effects of Perceiving Color on Psychological Functioning.” Annual Review of Psychology 65: 95 – 120. Fetterman, A. K., M. D. Robinson, and B. P. Meier. 2012. “Anger as “Seeing Red”: Evidence for a Perceptual Association.” Cognition and Emotion 26: 1445– 1458. Gamst, F. C. 1975. “Rethinking Leach’s Structural Analysis of Color and Instructional Categories in Traffic Control Signals.” American Ethologist 2: 271– 296. Gerend, M. A., and T. Sias. 2009. “Message Framing and Color Priming: How Subtle Threat Cues Affect Persuasion.” Journal of Experimental Social Psychology 45: 999– 1002. Goethe, W. [1810]1967. Theory of Colors. London: Frank Cass. Griffith, L. J., and S. D. Leonard. 1997. “Association of Colors with Warning Signal Words.” International Journal of Industrial Ergonomics 20: 317– 325. Gue´guen, N. 2012. “Color and Women Attractiveness: When Red Clothed Women Are Perceived To Have More Intense Sexual Intent.” The Journal of Social Psychology 152: 261– 265. Hill, R. A., and R. A. Barton. 2005. “Red Enhances Human Performance in Contests.” Nature 435: 293. Kaya, N., and H. H. Epps. 2004. “Relationship Between Color and Emotion: A Study of College Students.” College Student Journal 38: 396– 405. Kaze´n, M., and J. Kuhl. 2005. “Intention Memory and Achievement Motivation: Volitional Facilitation and Inhibition as a Function of Affective Contents of Need-Related Stimuli.” Journal of Personality and Social Psychology 89: 426– 448. Klinger, M. R., P. C. Burton, and G. S. Pitts. 2000. “Mechanisms of Unconscious Priming: I. Response Competition, Not Spreading Activation.” Journal of Experimental Psychology: Learning, Memory, and Cognition 26: 441– 455. Leonard, S. D. 1999. “Does Color of Warning Affect Risk Perception?” International Journal of Industrial Ergonomics 23: 499– 504. Lichtenfeld, S., A. J. Elliot, M. A. Maier, and R. Pekrun. 2012. “Fertile Green: Green Facilitates Creative Performance.” Personality and Social Psychology Bulletin 38: 784– 797. Mayhorn, C. B., M. S. Wogalter, and E. F. Shaver. 2004. “What Does Code Red Mean?” Ergonomics in Design 12– 15. Mehta, R., and R. J. Zhu. 2009. “Blue or Red? Exploring the Effect of Color on Cognitive Task Performance.” Science 323: 1226– 1229. Meier, B. P., M. D. Robinson, and G. L. Clore. 2004. “Why Good Guys Wear White.” Psychological Science 15: 82 – 87. Miller, J. M., and C. Parent. 2006. “Appendix: Bibliography of Standards.” In Handbook of Warnings, edited by M. Wogalter, 841. Mahwah, NJ: LEA. Moller, A. C., A. J. Elliot, and M. A. Maier. 2009. “Basic Hue-Meaning Associations.” Emotion 9: 898–902. Pazda, A. D., A. J. Elliot, and T. Greitemeyer. 2012. “Sexy Red: Perceived Sexual Receptivity Mediates The Red – Attraction Relation in Men Viewing Women.” Journal of Experimental Social Psychology 48: 787– 790. Piotrowski, C., and T. Armstrong. 2012. “Color Red: Implications for Applied Psychology and Marketing Research.” Psychology and Education – An Interdisciplinary Journal 49: 55 – 57. Pryke, S. R. 2009. “Is Red an Innate or Learned Signal of Aggression and Intimidation?” Animal Behaviour 78: 393– 398. Schmidt, T. 2000. “Visual Perception without Awareness: Priming Responses by Color.” In Neural Correlates of Consciousness, edited by T. Metzinger, 157– 179. Cambridge, MA: MIT Press. Schuldt, J. P. in press. “Does Green Mean Healthy? Nutrition Label Color Affects Perceptions of Heatlhfulness.” Health Communications. Setchell, J. M., and E. Jean Wickings. 2005. “Dominance, Status Signals and Coloration in Male Mandrills (Mandrillus sphinx).” Ethology 111: 25 – 50. Soriano, C., and J. Valenzuela. 2009. “Emotion and Colour Across Languages: Implicit Associations in Spanish Color Terms.” Social Science Information 48: 421– 445. Valdez, P., and A. Mehrabian. 1994. “Effects of Color on Emotions.” Journal of Experimental Psychology: General 123: 394– 409. Whitfield, T. W., and T. J. Whiltshire. 1990. “Color Psychology: A Critical Review.” Genetic, Social, and General Psychology Monographs 116: 387– 412. Wogalter, M. S., M. J. Kalsher, L. J. Frederick, A. B. Magurno, and B. M. Brewster. 1998. “Hazard Level Perceptions of Warning Components and Configurations.” International Journal of Cognitive Ergonomics 2: 123– 143.
Appendix English version of the words used for Experiment 1 (translated from the original French): Safety words: quilt (couette), shelter (abris), family (famille), home (maison), refuge (refuge). Danger words: disease (maladie), peril (peril), poison (poison), emergency (urgence), threat (menace).
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Symbols used for Experiment 2
Ergonomics Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/terg20
Is red the colour of danger? Testing an implicit red–danger association a
ab
c
d
Karyn Pravossoudovitch , Francois Cury , Steve G. Young & Andrew J. Elliot a
Aix-Marseille Université, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France
b
Université du Sud Toulon Var, La Garde, France
c
School of Psychology, Fairleigh Dickinson University, Teaneck, 07666 NJ, USA
d
Department of Clinical and Social Science in Psychology, University of Rochester, 488 Meliora Hall, Rochester, NY 14620, USA Published online: 04 Mar 2014.
To cite this article: Karyn Pravossoudovitch, Francois Cury, Steve G. Young & Andrew J. Elliot (2014) Is red the colour of danger? Testing an implicit red–danger association, Ergonomics, 57:4, 503-510, DOI: 10.1080/00140139.2014.889220 To link to this article: http://dx.doi.org/10.1080/00140139.2014.889220
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Ergonomics, 2014 Vol. 57, No. 4, 503–510, http://dx.doi.org/10.1080/00140139.2014.889220
Is red the colour of danger? Testing an implicit red– danger association Karyn Pravossoudovitcha, Francois Curya,b, Steve G. Youngc and Andrew J. Elliotd* b
a Aix-Marseille Universite´, CNRS, ISM UMR 7287, 13288 Marseille Cedex 09, France; Universite´ du Sud Toulon Var, La Garde, France; cSchool of Psychology, Fairleigh Dickinson University, Teaneck, 07666 NJ, USA; d Department of Clinical and Social Science in Psychology, University of Rochester, 488 Meliora Hall, Rochester, NY 14620, USA
(Received 13 August 2013; accepted 18 January 2014)
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Research using participant’s self-reports has documented a link between red and danger. In this research, we used two different variants of a Stroop word evaluation task to test for the possibility of an implicit red– danger association using carefully controlled colour stimuli (equated on lightness and chroma). Experiment 1, using words as stimuli, yielded strong evidence of a link between red and danger, and weaker evidence of a green – safety association. Experiment 2, using symbols as stimuli, again yielded strong evidence of a link between red and danger; no green effects were observed. The findings were discussed in terms of the power and promise of red in signal communication. Practitioner Summary: This research documents an implicit association between red and danger. Our findings confirm the wisdom of using red to communicate danger in systematic signal systems, and suggest that red may be used more broadly in other communication contexts to efficiently convey danger-relevant information. Keywords: red; danger; implicit association; signal communication; green
1. Introduction Colour is ubiquitous in our perceptual world. The various colours we perceive not only have aesthetic value (varying in appeal and preference), but also have communication value, carrying different associations and meanings (Elliot and Maier 2012; Goethe [1810]1967; Hill and Barton 2005). In this research, we focus on the communication value of the colour red, specifically the possibility of an implicit link between red and danger. In daily life, red is commonly used to convey danger or danger-relevant concepts. Red is the prototypic colour of alarms, sirens, stop signals and warning signs that convey danger and the need for vigilant attention. This red – danger link is codified in the safety, security and warning systems of a number of different organisations (e.g. American National Standards Institute, U.S. Homeland Security, International Organization for Standardization, Ministe`re de l’Equipement et du Logement, Union Europe´enne; Mayhorn, Wogalter, and Shaver 2004; Miller and Parent, 2006). Red is used in language to refer to problematic or dangerous things or situations to avoid (e.g. ‘red flag’, ‘red herring’, ‘in the red’, ‘code red’ and ‘red handed’). Thus, an implicit red – danger association may form over time and repeated exposure through a process of societal conditioning. It is possible that the aforementioned societal uses of red may themselves be an extension of natural learning. Red is the colour of objectively dangerous things that people encounter in the environment, such as an angry face, exposed blood and fire (Changizi 2009), and even minimal exposure to such critical, survival-relevant stimuli could forge an implicit red – danger association. Furthermore, it is possible that the societal uses of red are an extension of basic physiological processes. In many non-human animals, including several species of ape, red on a conspecific is interpreted as a threat cue, signalling the dominance and/or attack-readiness of an opponent (Pryke 2009; Setchell and Jean Wickings 2005); humans may likewise possess a biologically engrained predisposition to associate red with danger. Thus, both learning-based and biological considerations suggest that red may be linked to danger in a deep, implicit fashion. The existing research on the link between red and danger has primarily been conducted in ergonomics, and has focused exclusively on participant’s self-reports. This research typically involves displaying ‘signal’ words such as Danger, Caution or Attention, on different coloured backgrounds, and having participants rate their perception of the degree of hazard or risk being communicated. It is the red – danger combination that receives the highest hazard and risk ratings in these studies (Borade, Bansod, and Gandhewar 2008; Braun and Silver 1995; Chapanis 1994; Griffith and Leonard 1997; Leonard 1999; Wogalter et al. 1998). Research has yet to be conducted on the red –danger link using methods designed to assess implicit associations. Nevertheless, a few related studies have appeared in the literature and may be noted herein. Moller, Elliot, and Maier (2009)
*Corresponding author. Email: [email protected] q 2014 Taylor & Francis
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used a variant of the Stroop word evaluation task to document that red facilitates responses to negatively valenced words, particularly failure, and inhibits responses to positively valenced words, particularly success (see also Mehta and Zhu 2009; Piotrowski and Armstrong 2012). Fetterman, Robinson, and Meier (2012) used a similar paradigm to establish an implicit association between red and anger. Soriano and Valenzuela (2009) used a version of the Implicit Association Test to demonstrate a link between red and potency. In this research, we used variants of the Stroop word evaluation task to test whether the colour red facilitates responses to danger words (Experiment 1) and danger symbols (Experiment 2). Based on response competition logic (Klinger, Burton, and Pitts 2000), we reasoned that if red is associated with danger, then the simultaneous presentation of red and danger words (e.g. poison) or danger symbols (e.g. a skull and crossbones) should facilitate categorisation relative to other combinations of colours and words/symbols. We used green and grey as control colours. Green is an optimal chromatic contrast to red, because red and green are opposing colours in well-established colour models, and green can take on the opposite meaning of danger, namely safety (as well as peace, calmness and hope; Chan and Courtney 2001; Clarke and Costall 2008; Kaya and Epps 2004). Grey is an optimal achromatic contrast to red, because grey can be matched to chromatic colours on lightness. The extant literature on red and danger is not only limited in relying exclusively on participant’s self-reports, but it is also limited in that none of the existing research has systematically controlled for the lightness and chroma of the colour stimuli when examining hue. This is important, because it makes prior research difficult to interpret due to inevitable confounds between the three colour properties (see Valdez and Mehrabian 1994; Whitfield and Wiltshire 1990). For example, prototypic red is relatively low in lightness and high in chroma, so it is possible that the purported red –danger associations observed in the prior work using prototypic colour stimuli actually represent lightness or chroma effects (i.e. a lightness –danger or chroma – danger association, rather than a hue – danger association). If so, testing for hue –danger associations with red and other hues equated on lightness and chroma would yield null results. In both of the present experiments, red and green were equated on lightness and chroma, and red, green and grey were equated on lightness (grey has no chroma), thereby affording a clear, unconfounded test of the red (hue) –danger association. 2.
Experiment 1
In Experiment 1, danger words and safety words were presented in red, green and grey, and participants categorised them as danger related or safety related. Of foremost interest was whether danger words in red would be categorised most quickly. Facilitation for the green – safety combination and inhibition for the red – safety combination were also examined; grey was thought to have no relevant colour associations and, therefore, was used to anchor any red or green effects. 2.1
Method
2.1.1 Participants and process Thirty (17 female) undergraduates (mean age ¼ 24.2 years) participated. All were native French speakers, had no languagerelated disabilities and were not red – green colour deficient (as indicated by self-report after the experiment). In this and the subsequent study, we report all data exclusions, all manipulations and all measures; sample sizes were set a priori at 30 participants, based on a target of 0.80 power with medium effects sizes (at minimum) anticipated. 2.1.2 Stimuli and pilot test Ten adjectives were used as lexical stimuli (see the Appendix for an English translation of the original French), five denoting danger (disease, peril, poison, emergency and threat) and five denoting safety (quilt, shelter, family, home and refuge). The danger and safety words did not differ in word length (M ¼ 6.2 for each). The words were rated by 64 (44 female) pilot participants for the degree to which they were danger related and safety related (1, not at all; 6, extremely). The danger words were rated as more danger related (M ¼ 5.28, SD ¼ 0.47) than the safety words (M ¼ 1.72, SD ¼ 0.38), t ¼ 38.56, p , 0.001; the safety words were rated as more safety related (M ¼ 4.60, SD ¼ 0.54) than the danger words (M ¼ 1.80, SD ¼ 0.48), t ¼ 28.20, p , 0.001. 2.1.3
Design and procedure
The experiment had a 2 (word type: danger vs. safety) £ 3 (colour: red vs. green vs. grey) repeated measures design. It consisted of 180 trials divided into three blocks. Within a block, each danger and safety word was presented twice in each colour (for a total of six presentations of each word) in random order on a white computer screen. A GretagMacbeth (X-Rite) Eye-One Pro spectrophotometer (Munich, Germany) was used with a trial-and-error procedure (see Elliot and
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Maier 2014) to select colours equated on lightness and chroma at the spectral level (red: LCh[64.9/76.3/32.5], green: LCh [65.5/75.6/145.6], grey: LCh[65.2/ – /297.1]); equated means functionally equivalent (within 2.0 units). Participants’ task was to press a labelled key to indicate whether the word was danger related or safety related. The label position was counterbalanced across participants. For each trial, a fixation circle appeared for 500 ms, then a word appeared until a response was made or 5000 ms elapsed. The inter-trial interval was 1000 ms. Inaccurate (4.96%) responses (Kaze´n and Kuhl 2005) were omitted a priori. Thirty practice trials with the danger-related and safety-related words preceded the experiment.
Preliminary analyses in this and the subsequent experiment treating participant sex as a factor found no main effects, nor did sex moderate the theoretically central interaction; as such, sex was not considered further. Participants’ reaction times to categorise the words were submitted to a 2 (word type) £ 3 (colour) repeated measures ANOVA. The analysis revealed a significant main effect of word type, F(1, 29) ¼ 12.89, p ¼ 0.001, h2p ¼ 0:31, indicating that participants were faster in categorising safety words (M ¼ 643.64 ms, SD ¼ 91.77) than danger words (M ¼ 671.55 ms, SD ¼ 104.99). The main effect of colour was not significant, F(2, 58) ¼ 1.87, p ¼ 0.16. More importantly, a significant word type £ colour interaction, F(2, 58) ¼ 25.97, p , 0.001, h2p ¼ 0:47, indicated that participants were faster in categorising danger words presented in red (M ¼ 642.85 ms, SD ¼ 103.98) versus green (M ¼ 693.93 ms, SD ¼ 111.21), t(29) ¼ 4.86, p , 0.001, or grey (M ¼ 677.87 ms, SD ¼ 111.99), t(29) ¼ 4.73, p , 0.001 (see Figure 1). Although not significant, there was a trend for danger words presented in green to be categorised more slowly than danger words presented in grey, t(29) ¼ 1.75, p ¼ 0.09. For safety words, a different pattern emerged. Participants were slower in categorising words presented in red (M ¼ 657.64 ms, SD ¼ 97.77) than in green (M ¼ 627.10 ms, SD ¼ 87.99), t(29) ¼ 3.64, p , 0.001, but comparing safety words presented in red versus grey (M ¼ 646.19 ms, SD ¼ 99.45) revealed no significant difference, t(29) ¼ 1.46, p ¼ 0.15. The categorisation times for safety words presented in green and grey significantly differed, t(29) ¼ 2.82, p ¼ 0.008. In sum, the results indicated that red was positively associated with danger, as threat words were categorised more quickly in red than in green and grey. In addition, green was shown to be positively associated with security, as comfort words were categorised more quickly in green than in red and grey. 2.2.2
Ancillary analyses: errors
Although errors were infrequent, we conducted ancillary analyses to explore whether participants made systematic errors when categorising the words. A 2 (word type) £ 3 (colour) repeated measures ANOVA on errors revealed a significant main effect of word type, F(1, 29) ¼ 8.21, p ¼ 0.008, h2p ¼ 0:22, indicating that participants made more mistakes in categorising safety words (M ¼ 5.27, SD ¼ 4.83) than danger words (M ¼ 3.67, SD ¼ 4.34). The main effect of Colour was not significant, F(2, 58) ¼ 0.78, p ¼ 0.46. More importantly, a significant word type £ colour interaction, F(2, 800 750 Reaction time
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2.2 Results and discussion 2.2.1 Primary analyses: reaction times
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700 650 600 550 500 SAFETY
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Figure 1. (Colour online) Mean response latencies for danger and safety words presented in red, green and grey. The pattern of means for each danger word and each safety word was the same as the aggregate pattern with one exception: Participants were not slower to categorise the word family in red versus grey.
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58) ¼ 13.10, p , 0.001, h2p ¼ 0:31, indicated that participants made more mistakes when danger words were presented in green (M ¼ 1.83, SD ¼ 2.28), t(29) ¼ 3.67, p ¼ 0.001, and grey (M ¼ 1.20, SD ¼ 1.58), t(29) ¼ 2.29, p ¼ 0.03 than in red (M ¼ 0.63, SD ¼ 1.22). There was a non-significant trend for participants to make more errors for danger words presented in green than in grey, t(29) ¼ 1.82, p ¼ 0.08. When examining responses to safety words, participants made more mistakes when the words were presented in red (M ¼ 2.63, SD ¼ 2.51) versus green (M ¼ 1.10, SD ¼ 2.04), t(29) ¼ 4.10, p , 0.001 or in grey (M ¼ 1.53, SD ¼ 1.25), t(29) ¼ 2.58, p ¼ 0.02. There was no difference between safety words presented in green versus grey, t(29) ¼ 1.35, p ¼ 0.19. These results supplement the primary findings for reaction time, showing that participants made errors in a systematic manner consistent with the notion that red conveys danger relative to green and grey. With regard to errors on safety words, the pattern is somewhat different from that obtained in the primary analyses; here there is evidence for red – safety inhibition, rather than green– safety facilitation.
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3.
Experiment 2
Experiment 2 sought to replicate Experiment 1 using symbols rather than words. Danger and non-danger symbols were presented surrounded by red, green or grey, and participants’ task was to categorise them as danger related or non-danger related; non-danger related rather than safety related was used as the categorisation choice because standardised safety symbols are not available in international classifications. In addition, this design feature facilitates clarity of interpretation in that any observed effect must be due to danger (not safety). 3.1
Method
3.1.1 Participants Thirty (15 female) undergraduates (mean age ¼ 24.8 years) participated. They were native French speakers, had no language-related disabilities and were not red – green colour-blind. 3.1.2
Stimuli and pilot test
Ten symbols were used as stimuli (see the Appendix), five denoting danger (from Union Europe´enne) and five denoting non-danger (from Ministe`re de l’Equipement et du Logement). The symbols were rated by 65 (41 female) pilot participants for the degree to which they were danger related (1, not at all; 6, extremely). The danger symbols were rated as more danger related (M ¼ 5.43, SD ¼ 0.93) than were the non-danger symbols (M ¼ 1.28, SD ¼ 0.71), t ¼ 63.33, p , 0.001. 3.1.3 Design and procedure The experiment had a 2 (symbol type: danger vs. non-danger) £ 3 (colour: red vs. green vs. grey) repeated measures design. It consisted of 180 trials divided into three blocks. Within a block, each danger and non-danger symbol was presented six times (twice surrounded by each colour) in random order on a white computer screen. The same colour values as used in Experiment 1 were used in this experiment. Participants’ task was to press a labelled key to indicate whether the symbol was danger related or non-danger related. The label position was counterbalanced across participants. For each trial, a fixation circle appeared for 500 ms, then a symbol appeared until a response was made or 5000 ms elapsed. The inter-trial interval was 1000 ms. Inaccurate (2.94%) responses were omitted a priori. Thirty practice trials with the danger-related and non-danger-related symbols preceded the experiment. 3.2
Results and discussion
3.2.1 Primary analyses: reaction times Participants’ reaction times to categorise the symbols were submitted to a 2 (symbol type) £ 3 (colour) repeated measures ANOVA. The analysis revealed a significant main effect of symbol type, F(1, 29) ¼ 5.33, p ¼ 0.028, h2p ¼ 0:16, indicating that participants were faster in categorising danger symbols (M ¼ 529.72 ms, SD ¼ 55.39) than non-danger symbols (M ¼ 541.66, SD ¼ 11.54). The main effect of colour was not significant, F(2, 58) ¼ 0.41, p ¼ 0.67. More importantly, a significant symbol type £ colour interaction, F(2, 58) ¼ 22.54, p , 0.001, h2p ¼ 0:44, indicated that participants were faster in categorising danger symbols surrounded by red (M ¼ 517.40 ms, SD ¼ 55.17) versus green (M ¼ 538.22 ms, SD ¼ 60.22), t(29) ¼ 4.51, p , 0.001, or grey (M ¼ 533.53 ms, SD ¼ 56.10), t(29) ¼ 3.58, p ¼ 0.001 (see Figure 2). There was no difference between danger symbols surrounded by green versus grey, t(29) ¼ 1.22, p ¼ 0.23.
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DANGER
NON-DANGER Symbol type
Figure 2. (Colour online) Mean response latencies for danger and non-danger symbols surrounded by red, green and grey. The pattern of means for each danger symbol and each safety symbol was the same as the aggregate pattern.
For non-danger symbols, participants were slower when the symbols were surrounded by red (M ¼ 557.41 ms, SD ¼ 63.57) versus green (M ¼ 530.06 ms, SD ¼ 64.27), t(29) ¼ 5.12, p , 0.001, or grey (M ¼ 537.51 ms, SD ¼ 69.60), t(29) ¼ 3.14, p ¼ 0.004. Unlike Experiment 1, there was no difference between non-danger symbols surrounded by green versus grey t(29) ¼ 1.41, p ¼ 0.17; this is likely due to the control stimuli being neutral, rather than positive in valence (as in Experiment 1). In sum, the results indicated that red was positively associated with danger, as danger-related symbols were categorised faster on red than on green or grey backgrounds. Furthermore, reaction times to non-danger symbols were inhibited when they were presented on a red background compared with both on a green or grey background. This experiment did not yield any green effects, most likely due to the use of neutral, rather than safety-related target stimuli. 3.2.2 Ancillary analyses: errors As in Experiment 1, we conducted ancillary analyses to test whether participants’ errors were systematically influenced by colour. A 2 (symbol type) £ 3 (colour) repeated measures ANOVA on errors revealed a significant main effect of colour, F(2, 58) ¼ 5.59, p ¼ 0.006, h2p ¼ 0:16, indicating that participants made more mistakes when the symbol was presented surrounded by red (M ¼ 2.27, SD ¼ 2.24) versus green (M ¼ 1.63, SD ¼ 1.61) or grey (M ¼ 1.40, SD ¼ 1.48). The main effect for symbol type was not significant, F(1, 29) ¼ 0.004, p ¼ 0.95. More importantly, a significant symbol type £ colour interaction, F(2, 58) ¼ 6.59, p ¼ 0.003, h2p ¼ 0:19, was revealed. Colour had no impact on participants’ errors for danger-related words (all ps . 0.13). However, colour did influence categorisation accuracy for non-danger words; specifically, participants made more mistakes when non-danger symbols were surrounded by red (M ¼ 1.57, SD ¼ 2.01) versus green (M ¼ 0.57, SD ¼ 0.90), t(29) ¼ 3.26, p ¼ 0.003, or grey (M ¼ 0.50, SD ¼ 0.90), t(29) ¼ 3.44, p ¼ 0.002. There was no difference between non-danger symbols surrounded by green versus grey, t(29) ¼ 0.35, p ¼ 0.73. These results supplement the primary findings for reaction time. Participants were most likely to mistakenly categorise a non-danger symbol as danger related when it was presented on a red, relative to green or grey, background. 4. General discussion The results from our two experiments provided strong evidence of a red –danger association. Red was linked to danger across two different types of stimuli – lexical and pictorial – and across two different types of dependent measures – reaction times and number of errors. A green –safety association was observed in Experiment 1, although this was only supported by reaction time data, not error data. These findings for red are consistent with those observed in the ergonomics literature by a number of researchers (e.g. Chapanis 1994; Leonard 1999; Wogalter et al. 1998). However, the prior work focused exclusively on self-reported associations between red and danger-relevant concepts, whereas this research used a modified Stroop procedure to document the red – danger association implicitly. Another important contribution of the present, relative to the prior, work is that our findings were obtained using hue stimuli systematically equated for lightness and chroma at the spectral level.
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By rigorously controlling for lightness and chroma, this research was able to rule out, for the first time, alternative explanations based on lightness –danger and chroma – danger associations. This methodological improvement led to a clear, unconfounded demonstration of a red – danger association, but also left open the question of which type of red is most strongly connected to the concept of danger. In future work it would be helpful to conduct an additional series of experiments in which the red hue is held constant while lightness and chroma are systematically varied in different ways, in order to determine the precise variant of red that conveys danger most clearly and quickly. Our findings add to a growing stream of evidence converging across multiple literature (e.g. the psychological literature, the anthropological literature, the non-human primate literature; Elliot and Maier 2012; Hill and Barton 2005; Setchell and Jean Wickings 2005), pointing to the signal value of red. Although we think it likely that the red – danger link observed herein has roots in biology, as well as learning processes (see Changizi 2009; Elliot and Maier 2014), it is important to highlight that our research was not designed to test this assumption. It is possible that the popular use of red to convey danger-relevant concepts initially emerged randomly, and only became deeply embedded (i.e. implicit) over time through conditioning processes. Future research is needed to begin to examine the ultimate source of the implicit red –danger link, perhaps by conducting cross-cultural investigations, or by creating novel colour –danger associations in the laboratory and comparing and contrasting their properties with the focal red –danger association. Future work would also do well to examine other implicit associations to red that might be derived from the non-human primate literature as well, such as red and sexual receptivity (Gue´guen 2012; Pazda, Elliot, and Greitemeyer 2012). In our experiments, participants made categorisations based on the focal stimulus feature, danger, not hue, which was an (ostensibly) irrelevant stimulus feature. Nevertheless, hue produced effects, suggesting not only that hue was processed in obligatory fashion, but also that the meaning linked to hue was likely activated implicitly. This is impressive evidence in support of the implicit nature of the observed association (Meier, Robinson, and Clore 2004; Moller, Elliot, and Maier 2009), but additional evidence using other, conceptually related, methodologies (e.g. a lexical decision task, an implicit association task) could also be sought to further bolster the case. Most impressive of all would be to test the automaticity of the red –danger association using non-conscious colour priming procedures, such as those utilised in research by Schmidt (2000). Experiment 1 yielded tentative evidence for an implicit green –safety association, which is consistent with some research on self-reported colour –meaning associations (Chan and Courtney 2001). Green is beginning to get more attention in the colour literature, as researchers are starting to consider the possibility that green may also, at times, serve as an implicit cue that exerts a subtle influence on affect cognition, and behaviour (Akers et al. 2012; Lichtenfeld et al. 2012; Schuldt in press). However, we suspect that the power, breadth and applicability of green’s meaning and influence will be far less than that of red. Many aspects of biology, culture and language point to red as a colour of particular poignancy and prominence (see Elliot and Maier 2014). The real-world implications of our findings are straightforward, particularly with regard to signal communication. Many systematic signal systems use red to communicate danger-relevant information, and regardless of the ultimate source of the red – danger link, our data confirm the wisdom of using red for this purpose. Dangerous situations sometimes require quick, efficient responding, and red seems to be the optimal colour to facilitate such responding. As noted earlier, future research is needed to determine what precise variant of red (in terms of lightness and chroma) best facilitates responding; this would then be the colour of choice for use in brake lights, traffic lights and related signals using red coloration (see Changizi et al. 2014, for additional, related ideas for future research and application). Red may be useful as a danger cue in other communication contexts beyond formal signage or signal systems. Researchers are beginning to explore such possibilities, and are finding, for example, that a red background coupled with a loss-framed message is particularly persuasive in vaccination appeals (Chien 2011, 2013; Gerend and Sias 2009). The communication value of red has been recognised for centuries (Gamst 1975; Goethe [1810]1967), but we also think the breadth of applicability of this value has been under-appreciated. We believe that this is changing, as researchers begin to empirically document the presence and potential utility of colour – meaning associations. References Akers, A., J. Barton, R. Cossey, P. Gainsford, M. Griffin, and D. Micklewright. 2012. “Visual Color Perception in Green Exercise: Positive Effects on Mood and Perceived Exertion.” Environmental Science and Technology 46: 8661– 8666. Borade, A. B., S. V. Bansod, and V. R. 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Appendix English version of the words used for Experiment 1 (translated from the original French): Safety words: quilt (couette), shelter (abris), family (famille), home (maison), refuge (refuge). Danger words: disease (maladie), peril (peril), poison (poison), emergency (urgence), threat (menace).
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Symbols used for Experiment 2
