This paper will discuss the psychology of perception, threshold, and emotion in interior glass design. Color theory and referenced material behind threshold will be presented, and the implication of threshold in the design and specification of glass in various architectural applications will be examined.


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Humans have the ability to discern color and contrast but there is a range of differences in colors and contrast that are not perceivable to the human brain. The signal strength between the differences has to be great enough for the mind to be able to conclude there is a difference. This phenomenon is known as threshold.


The emotional content of shapes and colors will also be investigated. What shapes and colors are most pleasing and how aesthetics impact the psychological state of occupants will be presented. Situational attributes provided by environmental conditions impact the behaviour of individuals.


The way people act can be significantly altered by involving authorized direction
and providing an environment that reinforces the desired behaviour.


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It thus becomes ultimately important that the design of interior spaces highlights and supports the ideal conditions matching the culture, experience, or wanted outcomes of occupants and visitors. There is a level of integrity and responsibility that must fall upon the architect or designer in meeting both corporate and societal needs in keeping with the greater good.


Experiments in Design Gone Wrong
In a series of controversial experiments, Milgram and others show that individuals tend to change the way they act due to situational variables that promote conformance and behavioural despite the dispositional attitudes present.


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 Figure 1. Anti-Reflective Glass Example


Humans tend to give over their decision making power, logic, and reason to the control of a higher authority if put in certain authority/ subordinate roles and provided with reinforcing environmental aesthetics, conditions, or situations.


Milgram went through great efforts in his experiments to create a simulated shock machine in a laboratory setting that was so real looking that it fooled two electrical engineers (Russell, 2011).


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 Picture 1. Blue and Green Lines are the Same Colour


In his experiments, Milgram would have a test participant issue a shock to an actor that appeared to be another test subject.


The shock was fake, but the actor made it appear to be real. A doctor or facilitator wearing a lab coat, holding a clip board, and providing the official authorization to continue onward would prompt the test participant to issue greater levels of corrective shocks to a the actor.


Part of the success of the experiments has been as much the acting and sensationalized production as the study itself (Reicher & Haslam, 2011).


The experiment shows how easily people are moved to do things that harm others and justify these actions through outside control. But, the experiment can also show authority how better to control the general public. Have we learned to be wary of authority, or have we gained useful insight into how authority can better control the public? Current research suggests continued support for control through environmental and authoritarian factors.


Navarick (2012) suggests that there are three stages in a decision making process of a participant in whether to withdraw from an experiment. The stages are priming (collecting evidence), decision (mental), and choice (action). Priming is where a person is affected by the situational factors such as aesthetics, design, colors, lighting, and the atmosphere created by the “set” and the people and processes within the environment.


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Figure 2. Relative Brightness of Common Lighting Situations


The situational priming is magnified by things such as salience of the evidence intuited through all the senses such as emotional experience, and visual, tactile, and auditory feedback.


The decision stage is where the participant decides what to do next. Another experiment utilizing authority and environmental situational factors to control the behaviour of test subjects was Zimbardo’s infamous Stanford prison experiment.


Students were randomly selected to play the role of guards or prisoners in a simulated prison environment. The prison guards became tortuous and embodied the behaviours of the provided situation.


Zimbardo was forced to stop the experiment by a graduate student as he and the participants had lost touch with reality and accepted the evils being perpetrated by the participants as tolerable behaviour in the given situation (McDermott, 2007).


Design for Good
The experiments showed that situational experience and atmosphere overwhelmed innate dispositions to move people to the actions and behaviour that the authority wanted. Since, situation trumps disposition, is not it the role of architects and designers to help create the wanted emotional response in those visiting, working within, or simply viewing the building?


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Figure 3. Storefront with Anti-Reflective Glass


That being the case, perception, threshold, colour, and shape all are important variables in framing the human emotions derived from architectural designs and specifically in glass design.


Glass can bring light, add clarity, provide colour, and create atmosphere through contrast, pattern, and shape. The simple synergy of space and its interaction with movement can tailor emotions and response. Creativity can be enhanced, performance benefited, and well- being safeguarded.


Context and Content
Feature saliency or the quality of a feature being noticeable and impactful is inversely proportional to the frequency of a feature’s appearance (Vasquez, 2010).


Little things, sparse usage, and unique features make a big difference to observers. Redundancy of colour or shapes tend to cause lost impact and may be overwhelming.


The environment created with situational context effects neural processing and impacts social perception (Lieberman, 2006).


When a building is designed with shapes and colours that move people to collaborative and positive outcomes, positive results ensue.


Emotional context of environment impacts the way humans perceive neutral faces (Mobbs, 2006).


A welcoming building design will predispose occupants to being more receptive of each other. A receptive building, a receptive organization, and a well-received client.


The Shape of Things
Certain shapes or features of designs are connected with protection, positive feelings,  and feminine qualities whereas other shapes or features of designs are associated with threat, negative feelings, and masculine characteristics (Palumbo, 2015).


Both male and female participants found curved designs to be more nurturing and welcoming than angular shapes (Palumbo, 2015). Shapes of objects, patterns, and designs are important in creating environmental emotional context.


Storefronts may have harsh angularity further aggravated by shiny lights bouncing off the exterior glass. The sharp shapes and corners may create an emotional response opposite of what is wanted; avoidance of angular and straight edges innately seen as teeth, razors, or knives and provoking a flight or fight response from consumers.


Softening of hard surfaces and reduction of angularity becomes a solution. If the glass was not noticeable in the above example, then attention of the consumer could be brought into the store. A subconscious emotional welcome may be felt as the colours, curves, and features of the store would be forefront in the senses.


Threshold: When does a Reflection Become Noticeable?
Humans have the ability to discern colour and contrast. For every light level, there is a range of colours and contrast differences that are unperceivable to the human brain. The signal strength between the differences has to be great enough for the mind to be able to conclude there is a difference. This phenomenon is known as threshold.


This threshold phenomenon is what sets anti-reflective glass types apart. Reflections become unnoticeable when they cause a contrast or color deviance of less than 0.5%.


In environments where the glass has been designed for high transparency, the light levels are similar on both sides. This is why it becomes important to utilize materials with the lowest reflectivity possible to minimize the chance for distraction.


Distractibility Index

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One of the standard measurements in colour matching taken from the textile industry is delta E (dEcmc) which is a calculation combining lightness or contrast and colour variance (Hunt, 2004).


While differences in contrast are more allowable than colour, there is an acceptable range set in commercial applications. Colour specialties industry standard treats a deviation of less than 0.5% dEcmc as being an indiscernible colour and contrast difference (Green, & MacDonald, 2002).


However, not all eyes are the same. In regards to contrast, the difference in lightness and darkness, there needs to be greater than a 1% difference in order for humans to see an apparent difference nearly 100% of the time (Malm, 1999).


According to Malm (1999), in cases of contrast level differences of less than 0.5%, the difference becomes not noticeable to nearly everyone:
- Under 0.5%, the reflection (contrasting light) becomes unseen
- Above 1.0%, the reflection (contrasting light) becomes 100% noticeable


Contrast Threshold of 1%
The ability to detect contrast differences is based upon visual perception sensitivity and delineates the threshold between what is visible and invisible (Pelli & Bex, 2013).


Since 1860, scientific tests and research have found and maintained that threshold contrast levels necessary for something to be seen is 1% for most objects within a wide variety of environments (Pelli & Bex, 2013).


A thorough review of past measurements show that the threshold contrast has remained at 1% independent of dimensions and light levels (Pelli & Bex, 2013).


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Figure 4. Left to Right Transition from 0% to 10% White and 0% to 4% White


The simple test used for research of this phenomenon consists of two candles of the same light level being used to illuminate a screen or wall. One has a simple solid and opaque cylinder place in front to cast a shadow on the screen.


By varying the distance of candles from the screen until the shadow is perceived or not perceived the ratio of light between the unobstructed screen and the shadow cast on the screen can be calculated.


The amount of light difference along the edge of the shadow is determined by the far candle with the opaque cylinder in front as the amount of light from a point source varies as a function of the inverse of the distance squared (Pelli & Bex, 2013). The measurement of threshold comes at the point when the observer can just barely see the shadow.


This technique consistently results in observation of a 1% threshold (Pelli & Bex, 2013). Other methods such as using a spinning disc with a black section of a slice that when spun created a black ring have also shown this 1% level as the threshold over a wide range of light levels (Pelli & Bex, 2013).


Colour Threshold of .44% to .69%
Colour differences are detected similarly to differences in contrast but become noticeable when the perceived colour shifts (not just brightness level) enough to reach threshold.


The human eye detects colours with differing specialised receptors which are excited by blue, green, and red wavelengths of light. Each receptor reacts similarly to colour and light level changes but follow the same general rules as threshold for contrast.


The required level of cone excitation change for threshold detection of colour signals remains equal for a given background excitation level (Jennings & Barbur, 2010).


Each cone reacts independently of each other in the level necessary for detection enabling predictive modelling of detection thresholds necessary for any specified background light level and colour (Jennings & Barbur, 2010).


S-cones are excited by blue wavelengths, M-cones are excited by green wavelengths, and L-cones are excited by red wavelengths. Research supports a significant and strong linear threshold relationship (r2=.90 and .94 respectively) between the M- and Lcone excitations changes required to differentiate between foreground and background colour and brightness levels (Jennings & Barbur, 2010). Blue cones are much less sensitive to excitation changes. The M (green) and L cones (red) required approximately .44% - .69% excitation change to reach threshold levels necessary to be detected (Jennings & Barbur, 2010).


Light is always reflecting from glass surfaces. The question is whether it is visible or invisible to the observer. When the level of reflection does not reach threshold, it is said to be invisible.


The contrast threshold of 1% and the colour threshold of .44% - .69% interplay in the effect reflections have on the observer when looking through glass. When the reflection causes a combined light or colour level difference that reaches threshold, the reflection becomes noticeable.


For simplification purposes, under .5% has been selected as below threshold for contrast and colour as represented in the findings of the referenced studies. Similarly, 1% threshold is presented as a level of contrast or colour difference where the change in level is apparent and seen by 100% of normal observers.


It is important to understand these ranges in respect to reflection. The reflection is analogous to the light shadow cast by the far candle in the prior referenced example. Reflections cause changes in perceived light levels, contrast, or colours if they reach the threshold level.


The Colour of Moods Colour Impacts Colour
The impact on colour reflections is equal in significance to the impact of glass nuances which may render a colour slightly askew. The colour rendering index of glass is one of the measurements which compares how closely objects will be to their true colour when seen through the glass.


Coatings, glass chemistry, and reflections may all have an impact on the perception of colour through the glass but most attention has only been paid to the colour change imparted by the physical glass itself and not the reflections.


Colours reflected from behind the observer may foul and obscure the true colours of the scene observed. There is not a measurement or index associated with this shift in perception relegated to coloured reflections but they are nonetheless important.


For instance, a colour next to a colour affects its appearance. A line may appear both blue and green depending on the colour next to it (Picture 1).


The line is the same colour but the Purple and orange colours frame the context in which the colour is viewed. The eye and mind automatically judge the line based upon the nearby reference changing what is seen. Reflections may also impact the colours seen through the glass in the same manner.


Not a Reflection of You
Invisible storefronts create a unique aesthetic appeal. With reflection reduced by up to more than 16 times when compared to uncoated float glass, product displays pop and architectural designs transcend nature. The store blends effortlessly with its surroundings becoming one with the square. Foot traffic swells. As a natural result your client smiles.


Views become breathless through antireflective glass. The type and application of anti-reflective coating can provide glare- free glass storefronts with visible light reflection ranging from less than 0.5% up to 4% as well as produce little to no discernable colour shift.


Anti-reflective storefronts are available in monolithic, tempered or laminated, and insulated units. With large formats also available, the many fabrication options give unrivalled flexibility in aesthetically pleasing applications.


Many glass fabricators stock and custom process anti-reflective glass to bring life to architectural designer creations. Imagine an environment where beauty flows effortlessly together without the harsh reflections of unforgiving float glass.


Figure 1 is an example of how anti-reflective glass creates separation without reflection.


Today’s anti-reflective coating technologies produce glass that limits glare and unsightly reflections in numerous unique applications.


These high-tech coatings remove glass distractions from picture frame glass allowing the artwork to leap off the wall and become the focus of attention. Anti-reflective storefronts invite customer attention and welcome passers-by to come in and shop.


When used in projection systems or displays, the light or visual media smoothly transmits through the glass capturing the viewer’s attention without double images or visual light-front interference.


Transparent Communication
Restaurants, boutiques, and image-conscience retail shops require their carefully- designed, visual display elements to be communicated in the most favourable light. Glass provides a weather-tight, physical barrier that still maintains a visual connection between the public and the store.


Unfortunately, traditional glass also creates a secondary plane of focus pulling attention away from what is in the store to the reflections on the glass surfaces. Anti-reflective glass can virtually eliminate the reflection enabling the store’s inner beauty to speak for itself. Traditional glass reflects 8% of the visible light. What does this really mean in real life?


Only 92% of the outside light source reaches the inside of the storefront and provides a maximum potential for surface viewing through the same glass of 84.6% since 8% of light suffers from internal reflection on the way back out. Maximum illuminance becomes 100% when no glass separates the light source and the object and no glass or substance separates the object and the observer.


Brightness and Reflection Issues
The relative brightness of typical outside ambient light is 10 to 300 times brighter than inside lighting on overcast and sunny days. Figure 2 indicates some common lighting situations and the relative brightness.


The impact that the interior lighting has on noticeable reflectance is negligible for a majority of occurrences. And, when a store is lit up at night, the inner beauty of the store is released to the street in awe inspiring artistry especially with anti-reflective glass.


Distractibility Index

The direct reflection ratio allows comparison of visible light-front distraction between differing solutions. This ratio of “reflection annoyance” can be measured and provide a “distractibility index” to compare different solutions. Simply put, the amount of reflection divided by the amount of maximum illuminance gives a ratio that is measured on a scale of 0 to ∞.


Zero would indicate that there is no reflectance no matter how much light reaches the objects within the storefront and back out to the observer. Infinity would indicate a perfect mirror where all light is reflected at the glass storefront and no light reaches the objects within the storefront and back out to the observer. How does anti-reflective glass impact the visual presence of a store, display, or building?


When undistracted viewing is desired, finding a solution that provides the minimum colour, contrast, and brightness differential is the answer. In the real world, the architect and designer have limitless options at their fingertips.


Figure 3 is a real life example of a storefront with a high performance anti-reflective coating that has visible light reflectance equal to only 0.5%. It allows display merchandise to be protected from the elements while the colours, textures, and beauty are breathtakingly presented without glare to distract.


Direct Reflection Ratio
DR = Direct Reflection (% of Source)
MI = Max Illuminance (% of Source)
DIR = DR/MI = Direct Reflection Ratio

As previously discussed, monolithic float glass has visible light reflectance of 8%. A maximum of 92% of the outside source light reaches the objects within the storefront.


Additionally, the brightness of the image of the objects as seen by the outside observer has been reduced by another 8% as the light passes again through the glass and another 8% of the visible light reflects back into the store.


Now, let’s calculate the ratio for a storefront with uncoated monolithic float glass:
DIR = DR/MI = Direct Reflection Ratio
Direct Reflection Ratio = 8%/84.6% = 9.5%

In this example, the amount of reflection distracts the observer from the object displayed within the storefront. The direct reflection already peaks at a substantial 8%.


But since the maximum illuminance is only 84.6%, the effect of the reflection is 9.5% of the value of maximum illuminance. When an object is brightly coloured the reflection annoyance is bad enough, but when a darker coloured object with fine detail and nuances is displayed, the “distractibility index” understates the problem.


Now, let’s calculate the ratio for a storefront the uses monolithic anti-reflective glass as shown in the photo:
DIR = DR/MI = Direct Reflectance Ratio
Direct Interference Ratio = 0.5%/99% = 0.51%


In this example, the lower amount of interference does not distract the observer from the object. The difference in “distractibility index” can be significant and the ability to see the item on display is increased dramatically. The two examples show a 1900% difference in harsh glare and bouncing light.


Anti-reflective glass provides this type of benefit. The lower the direct reflection ratio of the anti-reflection glass, the higher the ability of the observer to focus on the objects displayed within the storefront.


This threshold phenomenon is what sets anti-reflective glass types apart. Reflections become unnoticeable when they cause a contrast or colour deviance of less than 0.5%.


In environments where the glass has been designed for high transparency, the light levels are similar on both sides. This is why it becomes important to utilize the lowest reflectivity possible to minimize the chance for distraction.


The difference between 1.0% and 0.5% may not seem like a lot, but it is the difference between a reflection being 100% perceived and nearly imperceptible. In other words, 0.5% is nearly 0% and 1% is 100% - a huge difference in perception for such a small difference in surface reflection.


Figure 4 shows a white block transition within the darker rectangle above. The left most line represents 0% reflectance/contrast whereas the far right line represents 4% for the transition with the line segments shown. 100% of people surveyed saw contrast differences above 1% (third line from the left). To the left of the second line, the white block became completely unseen.


The long and the short of it is that antireflective glass is great when focus needs to be on the objects within the storefront, office, or display and not on the glass. Anti-reflective glass provides beauty by being invisible. It is most valuable when noticed the least. Antireflective glass allows more of what is being looked at to meet the eye. 


The article was based on a lecture presented at the GLASS PERFORMANCE DAYS 2019 Conference, which took place on June 26-28, 2019. Tampere, Finland


James R. Gulnick

– Malm, W. C.: Introduction to Visibility. National Park Service and Colorado State Institute for Research on the Atmosphere, Fort Collins, Colorado, 1999.
– Green, P., & MacDonald, L. W.: Colour Engineering: Achieving Device Independent Colour. Chichester: Wiley, 2002.
– Hunt, R. W. G.: The Reproduction of Colour. Chichester, West Sussex, England: John Wiley & Sons, 2004
– Jennings, B. J., & Barbur, J. L. (2010). Colour detection thresholds as a function of chromatic adaptation and light level. Ophthalmic & Physiological Optics, 30(5), 560-567.
– Pelli, D. G., & Bex, P. (2013). Measuring contrast sensitivity. Vision Research, 9010-14.
– Bocchiaro, P., & Zimbardo, P. G. (2010). Defying Unjust Authority: An Exploratory Study. Current Psychology, 29(2), 155-170. doi:10.1007/s12144-010-9080-z
– Lieberman, M. D. (2006). Neural bases of situational context effects on social perception. Social Cognitive and Affective Neuroscience, 1(2), 73-74. doi:10.1093/scan/nsl015
– McDermott, R. (2007). The lucifer effect: Understanding how good people turn evil – by philip zimbardo.
Political Psychology, 28(5), 644-646. doi:10.1111/j.1467-9221.2007.00597.x
– Mobbs, D., Weiskopf, N., Lau, H. C., Featherstone, E., Dolan, R. J., & Frith, C. D. (2006). The Kuleshov Effect: the influence of contextual framing on emotional attributions. Social Cognitive and Affective Neuroscience, 1(2), 95-106. doi:10.1093/scan/nsl014
– Navarick, D. J. (2012). Historical Psychology and Figure 4. Left to Right Transition from 0% to 10% White and 0% to 4% White the Milgram Paradigm: Tests of an Experimentally Derived Model of Defiance Using Accounts of Massacres by Nazi Reserve Police Battalion 101. Psychological Record, 62(1), 133-154.
– Navarick, D. J. (2009). Reviving the Milgram Obedience Paradigm in the Era of Informed Consent. Psychological Record, 59(2), 155-170.
– Palumbo, L., Ruta, N., & Bertamini, M. (2015). Comparing Angular and Curved Shapes in Terms of Implicit Associations and Approach/Avoidance Responses. Plos One, 10(10). doi:10.1371/journal.pone.0140043
– Reicher, S., & Haslam, S. (2011). After shock? Towards a social identity explanation of the Milgram ‘obedience’ studies. British Journal Of Social
Psychology, 50(1), 163-169. doi:10.1111/j.2044-8309.2010.02015.x
– Russell, N. (2011). Milgram’s obedience to authority experiments: Origins and early evolution. British Journal Of Social Psychology, 50(1), 140-162. doi: 10.1348/014466610X492205.
– Vazquez, E., Gevers, T., Lucassen, M., Weijer, J. V., & Baldrich, R. (2010). Saliency of color image derivatives: a comparison between computational models and human perception. Journal of the Optical Society of America A, 27(3), 613. doi:10.1364/josaa.27.000613


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