Carl Jones

Discrimination of oriented visual textures by poultry chicks

We investigated how poultry chicks discriminate textures of lines sharing a common orientation from textures of variably oriented lines. Stimulus colours along with illumination were adjusted to selectively stimulate different receptor mechanisms. Chicks could discriminate achromatic textures, but not textures isoluminant to the double cones that gave a long vs. medium wavelength chromatic signal, nor an intensity signal for the short and very-short wavelength cones. These results suggest that detection of line orientation and texture discrimination uses an achromatic signal derived either from the double cones, or summed outputs of long and medium wavelength sensitive single cones.

How Life History Influences Population Dynamics in Fluctuating Environments

A major question in ecology is how age-specific variation in demographic parameters influences population dynamics. Based on long-term studies of growing populations of birds and mammals, we analyze population dynamics by using fluctuations in the total reproductive value of the population. This enables us to account for random fluctuations in age distribution. The influence of demographic and environmental stochasticity on the population dynamics of a species decreased with generation time. Variation in age-specific contributions to total reproductive value and to stochastic components of population dynamics was correlated with the position of the species along the slow-fast continuum of life-history variation. Younger age classes relative to the generation time accounted for larger contributions to the total reproductive value and to demographic stochasticity in “slow” than in “fast” species, in which many age classes contributed more equally. In contrast, fluctuations in population growth rate attributable to stochastic environmental variation involved a larger proportion of all age classes independent of life history. Thus, changes in population growth rates can be surprisingly well explained by basic species-specific life-history characteristics.

Colour categorization by domestic chicks.

Spectral stimuli form a physical continuum, which humans divide into discrete non–overlapping regions or categories that are designated by colour names. Little is known about whether non–verbal animals form categories on stimulus continua, but work in psychology and artificial intelligence provides models for stimulus generalization and categorization. We compare predictions of such models to the way poultry chicks (Gallus gallus) generalize to novel stimuli following appetitive training to either one or two colours. If the two training colours are (to human eyes) red and greenish–yellow or green and blue, chicks prefer intermediates, i.e. orange rather than red or yellow and turquoise rather than green or blue. The level of preference for intermediate colours implies that the chicks interpolate between the training stimuli. However, they do not extrapolate beyond the limits set by the training stimuli, at least for red and yellow training colours. Similarly, chicks trained to red and blue generalize to purple, but they do not generalize across grey after training to the complementary colours yellow and blue. These results are consistent with a modified version of a Bayesian model of generalization from multiple examples that was proposed by Shepard and show similarities to human colour categorization.

Population regulation of territorial species: both site dependence and interference mechanisms matter

Spatial patterns of site occupancy are commonly driven by habitat heterogeneity and are thought to shape population dynamics through a site-dependent regulatory mechanism. When examining this, however, most studies have only focused on a single vital rate (reproduction), and little is known about how space effectively contributes to the regulation of population dynamics. We investigated the underlying mechanisms driving density-dependent processes in vital rates in a Mauritius kestrel population where almost every individual was monitored. Different mechanisms acted on different vital rates, with breeding success regulated by site dependence (differential use of space) and juvenile survival by interference (density-dependent competition for resources). Although territorial species are frequently assumed to be regulated through site dependence, we show that interference was the key regulatory mechanism in this population. Our integrated approach demonstrates that the presence of spatial processes regarding one trait does not mean that they necessarily play an important role in regulating population growth, and demonstrates the complexity of the regulatory process.

Validation of a protocol for the assessment of skin temperature and blood flow in childhood localised scleroderma

Background/purpose: Localised scleroderma (LS) is the most common form of scleroderma seen in children, and usually presents unilaterally. Infrared thermography (IRT) and laser Doppler (LD) have both been reported to be useful in assessing the active, inflammatory stage of LS. We developed and validated a protocol using these techniques for the assessment of unilateral LS activity in children.

Generalization of Color by Chickens: Experimental Observations and a Bayesian Model

Sensory generalization influences animals’ responses to novel stimuli. Because color forms a perceptual continuum, it is a good subject for studying generalization. Moreover, because different causes of variation in spectral signals, such as pigmentation, gloss, and illumination, have differing behavioral significance, it may be beneficial to have adaptable generalization. We report on generalization by poultry chicks following differential training to rewarded (T+) and unrewarded (T−) colors, in particular on the phenomenon of peak shift, which leads to subjects preferring stimuli displaced away from T−. The first three experiments test effects of learning either a fine or a coarse discrimination. In experiments 1 and 2, peak shift occurs, but contrary to some predictions, the shift is smaller after the animal learned a fine discrimination than after it learned a coarse discrimination. Experiment 3 finds a similar effect for generalization on a color axis orthogonal to that separating T+ from T−. Experiment 4 shows that generalization is rapidly modified by experience. These results imply that the scale of a “perceptual ruler” is set by experience. We show that the observations are consistent with generalization following principles of Bayesian inference, which forms a powerful framework for understanding this type of behavior.

3D Imaging in Forensic Odontology

This paper describes the investigation of a new 3D capture method for acquiring and subsequent forensic analysis of bite mark injuries on human skin. When documenting bite marks with standard 2D cameras errors in photographic technique can occur if best practice is not followed. Subsequent forensic analysis of the mark is problematic when a 3D structure is recorded into a 2D space. Although strict guidelines (BAFO) exist, these are time‐consuming to follow and, due to their complexity, may produce errors. A 3D image capture and processing system might avoid the problems resulting from the 2D reduction process, simplifying the guidelines and reducing errors. Proposed Solution: a series of experiments are described in this paper to demonstrate that the potential of a 3D system might produce suitable results. The experiments tested precision and accuracy of the traditional 2D and 3D methods. A 3D image capture device minimises the amount of angular distortion, therefore such a system has the potential to create more robust forensic evidence for use in courts. A first set of experiments tested and demonstrated which method of forensic analysis creates the least amount of intra‐operator error. A second set tested and demonstrated which method of image capture creates the least amount of inter‐operator error and visual distortion. In a third set the effects of angular distortion on 2D and 3D methods of image capture were evaluated.

3D imaging for bite mark analysis

Abstract This work describes the investigation into a new 3D capture method for acquisition and subsequent forensic analysis of bite mark injuries on human skin. When documenting bite marks with standard 2D cameras, errors in photographic technique can occur if best practice is not followed. Subsequent forensic analysis of the mark is problematic when a 3D structure is recorded in a 2D space. A 3D image capture and processing system might avoid the problems resulting from the 2D reduction process, simplifying the guidelines and reducing errors. This paper reviews current 2D and three 3D capture methods and proposes a series of benchmarks for system assessment. This is followed by a series of performance evaluations of the existing current 2D and two 3D methods. Further proposed solutions include the design of a system specification for the practical reproducible acquisition of bite mark injuries and a review of the validation process for forensic evidence presented to the courts. The result of this work is that a 3D system is required to produce the correct 3D data of a bite mark and suspect dentition for forensic analysis. Such a system should be practical and consistent if it is to replace the current de facto 2D systems. The MAVIS hardware, for example, can be considered a practical and consistent solution for producing the required 3D image of a bite mark for analysis; however, the MAVIS hardware cannot produce a satisfactory 3D image of a dental cast. At present, a laser scanner is required to produce satisfactory results of a dental cast. Angular distortion and errors created by the user in 2D image capture can hinder the digital measurement process. 3D capture therefore introduces less operator error in the form of angular distortion.

Technical challenges for the construction of a medical image database

Infrared thermal imaging was first made available to medicine in the early 1960s. Despite a large number of research publications on the clinical application of the technique, the images have been largely qualitative. This is in part due to the imaging technology itself, and the problem of data exchange between different medical users, with different hardware. An Anglo Polish collaborative study was set up in 2001 to identify and resolve the sources of error and problems in medical thermal imaging. Standardisation of the patient preparation, imaging hardware, image capture and analysis has been studied and developed by the group. A network of specialist centres in Europe is planned to work to establish the first digital reference atlas of quantifiable images of the normal healthy human body. Further processing techniques can then be used to classify abnormalities found in disease states. The follow up of drug treatment has been successfully monitored in clinical trials with quantitative thermal imaging. The collection of normal reference images is in progress. This paper specifies the areas found to be the source of unwanted variables, and the protocols to overcome them.

Segmentation of Infrared Images Using Stereophotogrammetry

Image Segmentation has historically been a difficult part of Image Analysis in Infrared Imaging. Solutions include using a low-emissivity or cold material as a background or using a separate visual camera to perform image analysis tasks such as with the FLIR One. The proposed method utilises Stereophotogrammetry to obtain a depth map which is subsequently refined and segmented into fore- and background to give an accurate depiction of the object being imaged. The resulting 3D model can then be viewed on a computer for further analysis.