Ecological validity has typically been taken to refer to whether or not one can generalize from observed behavior in the laboratory to natural behavior in the world. Although common in current discussions of research, the idea of ecological validity has a long history in psychological thought. A brief historical examination of this idea reveals that concerns with ecological validity are evident in multiple dimensions of experimental work, including the nature of the experimental setting, the stimuli under investigation, and the observer's response employed as the measure. One problem with this multidimensionality, however, is that no explicit criteria have been offered for applying this concept to an evaluation of research. One consequence of this problem is that concerns with ecological validity can be raised in most experimental situations. This article includes a discussion of some demands of ecological validity and the nature of these different dimensions, as well as a critical evaluation of research on the development of mobility with respect to these constraints.

In the McGurk effect, perceptual identification of auditory speech syllables is influenced by simultaneous presentation of discrepant visible speech syllables. This effect has been found in subjects of different ages and with various native language backgrounds. But no McGurk tests have been conducted with prelinguistic infants. In the present series of experiments, 5-month-old English-exposed infants were tested for the McGurk effect. Infants were first gaze-habituated to an audiovisual /va/. Two different dishabituation stimuli were then presented: audio /ba/-visual /va/ (perceived by adults as /va/), and audio /da/-visual /va/ (perceived by adults as /da/). The infants showed generalization from the audiovisual /va/ to the audio /ba/-visual /va/ stimulus but not to the audio /da/-visual /va/ stimulus. Follow-up experiments revealed that these generalization differences were not due to a general preference for the audio /da/-visual /va/ stimulus or to the auditory similarity of /ba/ to /va/ relative to /da/. These results suggest that the infants were visually influenced in the same way as English-speaking adults are visually influenced.

Expectancy has long been of interest to psychologists and recently has become the focus of research in musical cognition. Four experiments are reported that investigated the formation of expectancies in musically trained listeners and performers. Experiments 1 and 2 examined the factors underlying the formation of melodic and harmonic expectancies, respectively. Both experiments found evidence for the psychological reality of constructs derived from the music-theoretic literature in expectancy formation. Experiment 3 investigated the generation of expectancies for a full musical context (one containing simultaneous melodic and harmonic information) and found that melody and harmony were perceptually independent, such that they combined additively in expectancy formation for a full musical context. Experiment 4 provided a convergent operation for the earlier studies by having skilled pianists perform their expectations for the same passages. These productions strongly correlated with the perceptual expectancies of Experiments 1-3. Taken together, these studies provide evidence for the existence of musical expectancy, as well as delineating some of the factors affecting its formation.