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Human body movements are especially effective in eliciting imitative responses. This thesis aims to establish why this is the case, and fundamentally, what this suggests about the mechanisms mediating imitation. Chapter 1 outlines theories which can account for this imitative bias, and highlights issues upon which these theories can be distinguished. Chapter 2 establishes whether the finding that responses are executed faster in response to stimuli of the same action type reflects an automatic tendency to imitate observed actions. On the basis of evidence to support this hypothesis, Chapters 3 and 4 use this reaction time measure to investigate imitation mechanisms. Chapter 3 addresses whether the human imitative bias emerges through top-down modulation of imitation mechanisms, on the basis of knowledge about whether stimuli are of human origin, or through perceptual properties of stimuli. These experiments suggest that automatic imitation effects are larger with human stimuli than robotic stimuli, but are unaffected by beliefs about stimulus identity, indicating that the imitative bias is driven by perceptual properties of stimuli. Chapter 4 asks why the perceptual properties of human stimuli are especially effective in eliciting imitative responses. On the basis of evidence suggesting that training can modulate imitation of robotic stimuli, this chapter supports the hypothesis that the imitative bias results from greater opportunity for associative learning with human stimuli. Chapter 5 investigates whether visuotactile integration can be modulated through training, in a similar way to visuomotor integration. By recording event-related brain potentials in response to tactile stimulation following visuotactile training, Chapter 5 indicates that visuotactile integration is modulated following training, but there are some differences in the influences of training with human and non-human visual stimuli. In summary, the results of the experiments reported in this thesis support the hypothesis that the human imitative bias emerges because of perceptual properties of human stimuli and greater opportunity to form associations between these stimuli and matching responses. These findings are consistent with the Associative Sequence Learning model of imitation. Visuotactile integration may also be understood with reference to associative learning.