Human speech conveys many forms of information, but for some exceptional individuals (synaesthetes), listening to speech sounds can automatically induce visual percepts such as colours. In this experiment, grapheme–colour synaesthetes and controls were asked to assign colours, or shades of grey, to different vowel sounds. We then investigated whether the acoustic content of these vowel sounds influenced participants' colour and grey-shade choices. We found that both colour and grey-shade associations varied systematically with vowel changes. The colour effect was significant for both participant groups, but significantly stronger and more consistent for synaesthetes. Because not all vowel sounds that we used are “translatable” into graphemes, we conclude that acoustic–phonetic influences co-exist with established graphemic influences in the cross-modal correspondences of both synaesthetes and non-synaesthetes.

Voice-induced synesthesia, a form of synesthesia in which synesthetic perceptions are induced by the sounds of people's voices, appears to be relatively rare and has not been systematically studied. In this study we investigated the synesthetic color and visual texture perceptions experienced in response to different types of “voice quality” (e.g., nasal, whisper, falsetto). Experiences of three different groups—self-reported voice synesthetes, phoneticians, and controls—were compared using both qualitative and quantitative analysis in a study conducted online. Whilst, in the qualitative analysis, synesthetes used more color and texture terms to describe voices than either phoneticians or controls, only weak differences, and many similarities, between groups were found in the quantitative analysis. Notable consistent results between groups were the matching of higher speech fundamental frequencies with lighter and redder colors, the matching of “whispery” voices with smoke-like textures, and the matching of “harsh” and “creaky” voices with textures resembling dry cracked soil. These data are discussed in the light of current thinking about definitions and categorizations of synesthesia, especially in cases where individuals apparently have a range of different synesthetic inducers.

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Body mass loss is frequently observed in breeding birds: whether this is an adaptive response to a change in the relative value of body stores and locomotion performance or a consequence of energetic constraint is still in debate. The male alone cares for most nests of the Eurasian dotterel Charadrius morinellus, although females assist at a proportion of nests. Energetic costs are probably high in the dotterel's arctic‐alpine environment and uniparental care restricts the foraging time available to meet these costs, so that incubating dotterel may have to fuel themselves partly using body stores. Nesting male dotterel lost 7.8% of their mass through the incubation period but were 6.8% heavier during periods of high food abundance. Males that were assisted in incubation by a female were 6.7% heavier than uniparental males. We conclude that, since dotterel were heavier when energetic constraints were lifted, mass loss through incubation was principally a consequence of energetic constraint, rather than adaptive mass optimisation.