The perceived colour of an object depends on its spectral reflection and spectral composition of the illuminant. Upon illumination change, the light reflected from the object also varies. This results in a different colour sensation if no colour constancy mechanism is available to form consistent representations of colours across various illuminants. We explore various colour constancy mechanisms in an agent-based model of foraging bees selecting flower colour based on reward. The simulations are based on empirically determined spatial distributions of various flower species in different plant communities, their rewards and spectral reflectance properties. Simulated foraging bees memorise the colours of flowers experienced as being most rewarding, and their task is to discriminate against other flower colours with lower rewards, even in the face of changing illumination conditions. The experimental setup of the simulation of bees foraging under different photic environments reveals the performance of various colour constancy mechanisms as well as the selective pressures on flower colour as a result of changing light. We compared the performance of von Kries photoreceptor adaptation and various computational colour constancy models based on the retinex theory with (hypothetical) bees with perfect colour constancy, and with modelled bees with colour blindness. While each individual model generated moderate improvements over a colour-blind bee, the most powerful recovery of reflectance in the face of changing illumination was generated by computational mechanisms that increase perceptual distances between co-occurring colours in the scene. We verified the results of our model using various comparisons between modelled bees’ performance and that predicted by our models, as well as exploring the implications for flower colour distribution in a variety of representative habitats under realistic illumination conditions.

No description available.

I work as a textile designer specialised in knitted textiles.In my designs Colours take an essential role.Where Knitting and colours are working as a team in order to reach my aesthetics.My aim is to provide new expressions and possibilities in knitting to the market, having for objective to show a different dimension to knitwear. / Program: Master in Textile Design

The goal of this thesis was to investigate the role of colour in visual selective attention. Previous experiments exploring this topic in tasks where location varied led to mixed results. Some studies only found evidence of colour as a guide to a specific location where selection then takes place (e.g., Nissen, 1985). Others reported an effect, but could not decide clearly if the benefit was due to direct selection of colour in perception (e.g., Humphreys, 1981). One major contributor to the inconsistencies of findings seems to be the confounding of colour and location in these tasks. For that reason the initial paradigm used here was a rapid serial visual presentation (RSVP) task. Previous studies using similar paradigms have found no evidence for direct selection by colour (Poder, 2001; Shih & Sperling, 1996), but in these studies advance colour information was of limited usefulness because it only reduced the set of candidate stimuli by half. To assess an effect of colour in selection similar to the one associated with location, in all experiments reported here valid colour information led to only one item, as is typical in location cuing tasks. The first RSVP experiment explored whether colour certainty improved performance over a colour uncertainty condition. Colour was the defining feature of the target participants had to discriminate. In one condition the target colour was certain; in the other it could be one of two colours. Performance was improved when participants could focus on one colour. Further experiments used colour not as a defining feature of the target but as additional information presented in the form of cues, similar to the typical use of location cues. The participants� task was to discriminate whether a target letter within the RSVP sequence appeared in its upper or lower case version, and an advance cue indicated the colour in which the target letter was most likely to occur. An accuracy benefit of valid colour information was found, supporting the hypothesis that colour cuing allows the direct selection of objects for further perceptual processing. In addition, an effect of invalid colour cues was also observed. Subsequent experiments investigated possible factors influencing the colour cuing effect. Together, task requirements and properties of the stimulus set were shown to have an influence on the effect size, whereas an increase in perceptual load had no impact. Furthermore, the colour cuing effect seems to be due partially to both automatic and strategic processes. In all these experimental variations, benefits of colour cuing remained, indicating that the effect is very robust. Colour cuing effects were also found in a design where location could vary, extending the previous findings from selection in the time domain to selection in space. The two last experiments investigated whether advance colour knowledge would also lead to a performance benefit in single item tasks. No effect of colour cuing was found, indicating that colour information is only helpful in multiple item displays when a selection of one target stimulus among distractor items is necessary.

This thesis investigates language acquisition and evolution, using the methodologies of Bayesian inference and expression-induction modelling, making specific reference to colour term typology, and syntactic acquisition. In order to test Berlin and Kay�s (1969) hypothesis that the typological patterns observed in basic colour term systems are produced by a process of cultural evolution under the influence of universal aspects of human neurophysiology, an expression-induction model was created. Ten artificial people were simulated, each of which was a computational agent. These people could learn colour term denotations by generalizing from examples using Bayesian inference, and the resulting denotations had the prototype properties characteristic of basic colour terms. Conversations between these people, in which they learned from one-another, were simulated over several generations, and the languages emerging at the end of each simulation were investigated. The proportion of colour terms of each type correlated closely with the equivalent frequencies found in the World Colour Survey, and most of the emergent languages could be placed on one of the evolutionary trajectories proposed by Kay and Maffi (1999). The simulation therefore demonstrates how typological patterns can emerge as a result of learning biases acting over a period of time. Further work applied the minimum description length form of Bayesian inference to modelling syntactic acquisition. The particular problem investigated was the acquisition of the dative alternation in English. This alternation presents a learnability paradox, because only some verbs alternate, but children typically do not receive reliable evidence indicating which verbs do not participate in the alternation (Pinker, 1989). The model presented in this thesis took note of the frequency with which each verb occurred in each subcategorization, and so was able to infer which subcategorizations were conspicuously absent, and so presumably ungrammatical. Crucially, it also incorporated a measure of grammar complexity, and a preference for simpler grammars, so that more general grammars would be learned unless there was sufficient evidence to support the incorporation of some restriction. The model was able to learn the correct subcategorizations for both alternating and non-alternating verbs, and could generalise to allow novel verbs to appear in both constructions. When less data was observed, it also overgeneralized the alternation, which is a behaviour characteristic of children when they are learning verb subcategorizations. These results demonstrate that the dative alternation is learnable, and therefore that universal grammar may not be necessary to account for syntactic acquisition. Overall, these results suggest that the forms of languages may be determined to a much greater extent by learning, and by cumulative historical changes, than would be expected if the universal grammar hypothesis were correct.

Architects and others choosingfacade colours using colour samples face difficulties whichprevious research has not addressed. This work aims to aid suchcolour design by exploring three main questions: 1. Is itpossible to survey and map out what colours people perceive onfacades observed under different conditions? If so, whatmethods can be used and it is possible to obtain results ofwider application? 2. How does the perceived colour of a facadevary with changing observation conditions? What is the impactof factors such as light conditions, viewing distance andsurrounding colours? 3. How does the perceived colour of thehouse, in different situations, differ from the colourcorresponding to the specification of the sample used forselection? Are there any recurring tendencies that can bepresented in a practically useful way? The work was based onabout 3600 observations of painted timber and rendered facades,made by both experienced colour researchers and "naïve"school students, with various daylighting conditions, viewingdistances and seasons. Colour specifications and discussions oncolour attributes were made within the conceptual framework ofthe Natural Colour System (NCS). Inherent colour was measuredby comparison with colour samples placed directly on the facadesurface. Six methods for determination of perceived colour weredeveloped and evaluated, along with a method for comparison ofperceived and inherent colour. A combination of all gave themost reliable results. Results showed some recurring tendenciesfor perceived colour to vary with viewing conditions, but thevariations were always smaller than the difference betweenperceived and inherent colour. Consistent variation patternsfor the difference between inherent and perceived colour werefound for both hue and nuance. Most obvious was that perceivedcolour always had less blackness than inherent colour. Possibleexplanations included differences between the outdoor viewingsituation and the standard situation where inherent colour isdefined, and the observer’s acquired sense of what colours"belong" outdoors. A fuller explanation would require furtherstudies such as of colour perception in different lightsituations, and of three dimensional context effects. Resultshave immediate applicability however; suitably illustrated andpublished, the variation patterns found could be of directpractical use in exterior colour design.

In digital environments, colour is used for many purposes: for example, to encode information in charts, signify missing field information on websites, and identify active windows and menus. However, many people have inherited, acquired, or situationally-induced Colour Vision Deficiency (CVD), and therefore have difficulties differentiating many colours. Recolouring tools have been developed that modify interface colours to make them more differentiable for people with CVD, but these tools rely on models of colour differentiation that do not represent the majority of people with CVD. As a result, existing recolouring tools do not help most people with CVD. To solve this problem, I developed Situation-Specific Modelling (SSM), and applied it to colour differentiation to develop the Individualized model of Colour Differentiation (ICD). SSM utilizes an in-situ calibration procedure to measure a particular user’s abilities within a particular situation, and a modelling component to extend the calibration measurements into a full representation of the user’s abilities. ICD applies in-situ calibration to measuring a user’s unique colour differentiation abilities, and contains a modelling component that is capable of representing the colour differentiation abilities of almost any individual with CVD. This dissertation presents four versions of the ICD and one application of the ICD to recolouring. First, I describe the development and evaluation of a feasibility implementation of the ICD that tests the viability of the SSM approach. Second, I present revised calibration and modelling components of the ICD that reduce the calibration time from 32 minutes to two minutes. Next, I describe the third and fourth ICD versions that improve the applicability of the ICD to recolouring tools by reducing the colour differentiation prediction time and increasing the power of each prediction. Finally, I present a new recolouring tool (ICDRecolour) that uses the ICD model to steer the recolouring process. In a comparative evaluation, ICDRecolour achieved 90% colour matching accuracy for participants – 20% better than existing recolouring tools – for a wide range of CVDs. By modelling the colour differentiation abilities of a particular user in a particular environment, the ICD enables the extension of recolouring tools to helping most people with CVD, thereby reducing the difficulties that people with CVD experience when using colour in digital environments.

<p>Architects and others choosingfacade colours using colour samples face difficulties whichprevious research has not addressed. This work aims to aid suchcolour design by exploring three main questions: 1. Is itpossible to survey and map out what colours people perceive onfacades observed under different conditions? If so, whatmethods can be used and it is possible to obtain results ofwider application? 2. How does the perceived colour of a facadevary with changing observation conditions? What is the impactof factors such as light conditions, viewing distance andsurrounding colours? 3. How does the perceived colour of thehouse, in different situations, differ from the colourcorresponding to the specification of the sample used forselection? Are there any recurring tendencies that can bepresented in a practically useful way? The work was based onabout 3600 observations of painted timber and rendered facades,made by both experienced colour researchers and "naïve"school students, with various daylighting conditions, viewingdistances and seasons. Colour specifications and discussions oncolour attributes were made within the conceptual framework ofthe Natural Colour System (NCS). Inherent colour was measuredby comparison with colour samples placed directly on the facadesurface. Six methods for determination of perceived colour weredeveloped and evaluated, along with a method for comparison ofperceived and inherent colour. A combination of all gave themost reliable results. Results showed some recurring tendenciesfor perceived colour to vary with viewing conditions, but thevariations were always smaller than the difference betweenperceived and inherent colour. Consistent variation patternsfor the difference between inherent and perceived colour werefound for both hue and nuance. Most obvious was that perceivedcolour always had less blackness than inherent colour. Possibleexplanations included differences between the outdoor viewingsituation and the standard situation where inherent colour isdefined, and the observer’s acquired sense of what colours"belong" outdoors. A fuller explanation would require furtherstudies such as of colour perception in different lightsituations, and of three dimensional context effects. Resultshave immediate applicability however; suitably illustrated andpublished, the variation patterns found could be of directpractical use in exterior colour design.</p>

Explaining the wide range of animal colouration in the natural world is a key issue in evolutionary biology. Bumble bees are often brightly coloured and show a range of colours and colour patterns in different species as well as considerable variation within species. The large garden bumble bee, Bombus ruderatus, is highly variable in its degree of black (melanic) colouration, with morphs ranging from the familiar yellow and black bands (banded) through intermediate forms to morphs that are totally melanic. The aim of this research was to determine what might be maintaining the colour polymorphism in populations of B. ruderatus in the South Island, New Zealand. Colouration of worker bees was measured using a digital photography method and found to be significantly different across sample sites. To look at potential adaptive functions of body colour in B. ruderatus, three hypotheses of thermoregulation, desiccation tolerance and Müllerian mimicry were tested by comparing patterns of variation in melanism to patterns of variation in climatic variables (temperature, rainfall, humidity) and abundance of conspecifics. In order to address the possibility that selectively neutral processes were more important than selection, the genetic structure of B. ruderatus populations was characterised and compared to the pattern of variation in melanism. The colouration of individuals from the same population collected at different times in the season was compared to evaluate whether body colour was plastic and any support for the genetic basis of melanism in B. ruderatus was also assessed by determining any relationship between relatedness and degree of melanism. The results suggest that differences in the degree of melanism between populations are greater than the differences expected through selectively neutral forces alone and, therefore, that the pattern of variation in melanism is likely a result of selection and/or phenotypic plasticity in addition to gene flow and genetic drift. Although a global model consisting of four climatic variables and the abundance of conspecifics explained a small proportion of the variation in melanism, no support was found for any specific hypothesis relating to the adaptive function for body colour. Instead the results suggest that some combination of factors, most likely including factors not measured in this study, is influencing the frequency of melanic morphs. In addition, there was evidence that body colour was influenced by phenotypic plasticity and that melanism has a low heritability in B. ruderatus. Taken together, these results imply that patterns of melanism across B. ruderatus populations are complex and it is likely that multiple factors are influencing melanism in concert.

No description available.