The present investigations were undertaken to compare interspecific communicative abilities of dogs and wolves, which were socialized to humans at comparable levels. The first study demonstrated that socialized wolves were able to locate the place of hidden food indicated by the touching and, to some extent, pointing cues provided by the familiar human experimenter, but their performance remained inferior to that of dogs. In the second study, we have found that, after undergoing training to solve a simple manipulation task, dogs that are faced with an insoluble version of the same problem look/gaze at the human, while socialized wolves do not. Based on these observations, we suggest that the key difference between dog and wolf behavior is the dogs' ability to look at the human's face. Since looking behavior has an important function in initializing and maintaining communicative interaction in human communication systems, we suppose that by positive feedback processes (both evolutionary and ontogenetically) the readiness of dogs to look at the human face has lead to complex forms of dog-human communication that cannot be achieved in wolves even after extended socialization.
Little is known about the development of the sensory systems of wolves. The timing of sensory development in wolves is usually extrapolated from studies on dogs, since they are members of the same species. However, early developmental differences between these two subspecies have already been identified. For example, wolves tend to approach and investigate objects in their environment 2 wk before dogs. These changes in developmental timing may play an important role in the behavioral differences between adult wolves and dogs. The purpose of this study is to compare the development of the sensory systems in wolves and dogs.
Responses of seven wolf pups and 43 dog pups to familiar and novel olfactory, auditory, and visual stimuli were tested weekly from 2–7 wk of age. Eleven wolf pups were also observed for orientation towards auditory and visual stimuli during 2-h sessions, 5 d a week, from 2–8 wk of age. These observations were supplemented by the daily records of caretakers.
The results suggest that wolves and dogs both develop olfaction by 2 wk, audition by 4 wk, and vision by 6 wk on average, despite the 2-wk shift in their ability to explore. This means that when wolves begin to explore at 2 wk, they are blind and deaf, and must rely primarily on their sense of smell. Thus, there is a significant alteration of how these subspecies experience their environment during the critical period of socialization. These findings lead to an alternative explanation for the difference in dogs' and wolves' abilities to form interspecies social attachments, such as those with humans.