Recent Research Projects

Goal inference for 'irrational' actions

Infants and adults are thought to infer the goals of observed actions by calculating the actions' efficiency as a means to particular external effects, like reaching an object or location. However, many intentional actions lack an external effect or external goal (e.g. dance). We show that for these actions, adults infer that the agents' goal is to produce the movements themselves: Movements are seen as the intended outcome, not just a means to an end. We find that observers infer movement-based goals to explain otherwise mysterious intentional actions: movements that are clearly intentional, but are not an efficient means to any plausible external goal. These findings expand models of goal inference to account for intentional yet 'irrational' actions, and suggest a novel explanation for overimitation as emulation of movement-based goals.

Paper: [Schachner & Carey, 2013; Cognition]
Related Poster:
[Schachner & Carey, 2011; CogSci]

Evolutionary origins of auditory-motor entrainment

The ability to entrain, or align movement, to an external auditory pulse has been repeatedly highlighted as uniquely human. In this line of work, we tested the hypothesis that entrainment evolved as a by-product of vocal mimicry. This hypothesis generates the strong prediction that only vocal mimicking animals should be able to entrain. We report two vocal mimicking nonhuman animals (parrots) that entrain to music, spontaneously producing synchronized movements resembling human dance. Furthermore, we test an extensive comparative data set from a global video database, including hundreds of species both capable and incapable of vocal mimicry. Despite the higher representation of vocal nonmimics in the database and comparable exposure of mimics and nonmimics to humans and music, only vocal mimics showed evidence of entrainment. Thus, entrainment is not unique to humans, and the distribution of entrainment across species supports the hypothesis that entrainment evolved as a by-product of selection for vocal mimicry.

Paper: [Schachner, Brady, Pepperberg & Hauser, 2009]
Supplemental information: [Supplement] [Table] [Video 1] [Video 2]
[YouTube Videos (.zip)]
Related Papers: [Schachner, 2013; Nova Acta Leopoldina NF]
[Schachner, 2012; Empirical Musicology Review]
[Schachner, 2010; Communicative & Integrative Biology]
Related Poster: [Schachner et al., 2008; Neuromusic III]

Infant-directed speech and social preferences

Adults across cultures speak to infants in a specific infant-directed manner, often termed 'musical speech' for its exaggerated prosody and slower, repetitive structure. We investigated whether infants use this manner of speech (infant- or adult-directed) to guide their subsequent visual preferences for social partners. We found that 5-month-old infants encode an individuals' use of infant-directed speech and adult-directed speech, and use this information to guide their subsequent visual preferences for individuals even after the speech behavior has ended. We suggest that use of infant-directed speech may act as an effective cue for infants to select appropriate social partners, allowing infants to focus their attention on individuals who will provide optimal care and opportunity for learning.

Paper: [Schachner & Hannon, 2011; Developmental Psychology]

Related Papers: [Trehub, Hannon & Schachner, 2010; Handbook of Music & Emotion]
Related Poster: [Schachner & Hannon, 2007; Cognitive Development Society]