Cryptic Patterning of Avian Skin Confers a Developmental Facility for Loss of Neck Feathering

Vertebrate skin is characterized by its patterned array of appendages, whether feathers, hairs, or scales. In avian skin the distribution of feathers occurs on two distinct spatial levels. Grouping of feathers within discrete tracts, with bare skin lying between the tracts, is termed the macropattern, while the smaller scale periodic spacing between individual feathers is referred to as the micropattern. The degree of integration between the patterning mechanisms that operate on these two scales during development and the mechanisms underlying the remarkable evolvability of skin macropatterns are unknown. A striking example of macropattern variation is the convergent loss of neck feathering in multiple species, a trait associated with heat tolerance in both wild and domestic birds. In chicken, a mutation called Naked neck is characterized by a reduction of body feathering and completely bare neck. Here we perform genetic fine mapping of the causative region and identify a large insertion associated with the Naked neck trait. A strong candidate gene in the critical interval, BMP12/GDF7, displays markedly elevated expression in Naked neck embryonic skin due to a cis-regulatory effect of the causative mutation. BMP family members inhibit embryonic feather formation by acting in a reaction-diffusion mechanism, and we find that selective production of retinoic acid by neck skin potentiates BMP signaling, making neck skin more sensitive than body skin to suppression of feather development. This selective production of retinoic acid by neck skin constitutes a cryptic pattern as its effects on feathering are not revealed until gross BMP levels are altered. This developmental modularity of neck and body skin allows simple quantitative changes in BMP levels to produce a sparsely feathered or bare neck while maintaining robust feather patterning on the body

Sign Theory: A Non-Extensional Theory of Preference

57 pagesA non-extensional theory of preference, called Sign Theory, is proposed and tested. Sign Theory considers preference construction as an evidence-building process, in which local valuation of evidence combines additively to form a global judgment. At the heart of this treatment is the notion that local evaluation generates positive or negative valuation outcomes (signs). Thus, signs are building blocks for preference construction. Study 1 confirmed the notion that valuation processes are based on signs derived from reference points. Studies 2 and 3 demonstrated the robustness and importance of the sign-frequency effect, which shows that the attractiveness of an option is positively related to the number of the positive signs, but negatively related to the number of negative signs. Studies 4 and 5 were designed to reduce the sign-frequency effect. Study 4 provided information about attribute weights to help participants appreciate the part-whole relationship between partitioned attributes and summarized attributes. In Study 5, decision makers were clearly informed about the two display formats of the same information. Nevertheless, in both studies, the presence of sign-frequency effects remained evident