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ISBN: 978-972-8939-25-0 © 2010 IADISdesign in 1988 I was referring to perceivable affordances. […].”. Other distinctions between theseapproaches are listed in Table 2 (McGrenere & Ho, 2009).Norman brought the concept to HCI in theTable 2. Comparison of Gibson’s x Norman’s affordancestransition of the 1 st and 2 nd paradigms, when theinfluence of human factors (and cognitivepsychology) and the goal to fit the relationshipbetween the human and computer were dominant.The example of Figure 1c shows that in the 3 rdparadigm, when technologies such as augmented andvirtual reality are present, the distinction betweenphysical and perceived affordances is not so clearanymore. In this example, an interface may beprojected anywhere, but the affordance to touch thedial with one finger is preserved.Gibson’s AffordanceOfferings or action possibilities inthe environment in relation to theaction capabilities of an actorIndependent of the actor’sexperience, knowledge, culture,or ability to perceiveExistence is binary – it exists or itdoes not existNorman’s AffordancePerceived properties that mayor may not actually existSuggestions or clues as tohow to use the propertiesCan be dependent on theexperience, knowledge, orculture of the actorCan make an action difficultor easySince Norman’s view, Hartson (2003), Vyas et al. (2006), Gaver (1991), Stamper (2001), Zhang (2006)among others considered cognitive aspects in their understanding of affordance and continued to expand theconcept including human aspects such as experience, knowledge, culture, and the social characteristic.Gaver (1991), for instance, proposes that a combination of affordance with the perceptual information aperson has about it suggests potentials for action, making interaction easy to learn and use. According to him,“affordances are properties of the world that are compatible with and relevant for the actors’ interaction,which, when perceptible, offer a link between the actors’ perception and action.”. Figure 1d is an example ofan affordance oriented by a particular situation: a washing machine was used to build a dog house, anunusual application that would hardly be afforded without an external motivation. Gaver’s proposal is also inthe transition between the 1 st and 2 nd paradigms, still applied to optimize the human–computer interaction.After years of confusion and misuse of the term by designers as Norman himself states (Norman, 1999),in 2008 he suggested replacing affordance with the term signifier. He argues that “the perceivable part of anaffordance is a signifier, and if deliberately placed by a designer, it is a social signifier” and asks to “forgetthe term affordances: what people need, and what design must provide, are signifiers. Because most actionswe do are social, the most important class of these are social signifiers. […] Social signifiers replaceaffordances, for they are broader and richer, allowing for accidental signifiers as well as deliberate ones,and even for items that signify by their absence.”. To exemplify, Norman (2008) describes the situationwhere the absence of people on a train platform may be a social signifier indicating that the train has alreadyleft. The social signifier includes culture and experiences, similarly to Stamper’s social affordance idea.Figure 1a. Physicalaffordance of a portablecomputerFigure 1b. Perceivedaffordance: highlight of abutton (www.paypal.com)3.2 Stamper’s Social AffordanceFigure 1c. Ex. of a gesture andaugmented reality UI (MITMedia Lab, 2010)Figure 1d. Example ofspecific perceivedaffordance (Street use,2010)To Stamper (2004), “All organisms, including human agents construct their perceptions of the only worldthey can know through their actions; they have to discover (or be taught, or inherit by instinct) whatinvariant repertoires of behaviour the world affords them (= the affordances); then they populate theirreality with those affordances that help them to survive”. Stamper associates the physical affordances withGibson's definition – linked to properties of the physical environment. They are social in nature, because theyare dependent on the knowledge that has been built up and handed down from generation to generation in asociety. Social affordances are repertories of behavior tuned to the social environment, valid for a certaincommunity, with a start and finish time, and a starting and finishing authority (Gazendam & Liu, 2005).186