Although it is a commonplace that small animals are more abundant than large ones, few attempts have been made to quantify this and none for non-mammalian species. This study uses estimates of animal density and body mass culled from 12 journals published between 1961 and 1978 to test and extend Damuth's relationship between population density and body size of herbivorous mammals. In general, his analysis is supported, for density usually declines roughly as W and poikilotherms maintain higher densities than homeotherms. However the residual variation is higher than Damuth's regressions might suggest and significant differences exist among animal groups. In particular, birds maintain much lower, and aquatic invertebrates much higher abundances than a general curve for all species would suggest. Carnivores are significantly rarer than herbivores. These relationships may be used to compare the average relative contributions of species of different size to community structure and function. Such relations also provide a necessary basis both for more complete empirical analyses of the determinants of animal abundance and for the construction of more realistic conceptual models in theoretical ecology.

Two groups of 20 infants aged 0; 3 experienced either conversational turn taking or random responsiveness of an adult. All infant vocalizations were counted and then each was categorized as a speech-like (syllabic) sound or a nonspeech-like (vocalic) sound. The results of this experiment indicated that turn taking caused changes in the quality of infant vocal sounds. When the adult maintained a give-and-take pattern, the infant produced a higher ratio of syllabic/vocalic sounds. The effect of turn taking on infant vocalizations was discussed in terms of its possible adaptive value for adult responsiveness.

The present research was designed to systematically examine consonant errors made by severely disabled readers in an attempt to clarify the nature of their underlying disability. In our first study, three groups of disabled readers were compared to both age-and reading-level matched controls on their performance reading a list of 96 one-syllable nonsense words. As predicted, subjects in all five groups made many more phonetic feature substitutions than orientation reversal substitutions. This is consistent with previous work indicating that reading errors typically result from linguistic-rather than visual-processing difficulties. Further, subjects from all three reading disabled groups, but not from the control groups, made more consonant addition errors than any other error type. A qualitative, post-hoc analysis of the errors suggested that these additions were quite systematic for the reading disabled subjects. The second study was designed as a replication and extension of the first. Results were consistent with those obtained in Study 1. These results are discussed with reference to the possible underlying cause(s) of severe reading disability.