Allocentric Perception in Primates - and the Role of Vision in the Evolution of Thought
This thesis explores the evidence of allocentric visual processing in primates with the purpose of illuminating a proposed co-evolution of more advanced visual perception and cognition in humans and closely related primates. The thesis is divided into three distinct parts, that in turn deal with three different aspects of this task. Part I reviews the last twenty years of research into the two visual systems hypothesis, proposed originally by Ungerleider and Mishkin in 1982, that separated the human visual system into two discrete subsystems named the dorsal and ventral streams. Different models for the functional subdivision of the human visual system are reviewed and discussed. The ventral stream is considered to handle allocentric visual processing, and is only found in primates, and it is argued that this is a prerequisite for visual object recognition and conscious sight, making this neurological pathway a stepping stone in the evolution of our cognitive systems. Part II considers the behavioural evidence of allocentric perception in different species of primates by linking such perception to different behavioural and cognitive abilities, and proposes a model to interpret the available data and guide further research into the visual capabilities of apes and monkeys. Part III discusses why allocentric perception is an important factor in the evolution of human cognition, and considers some more specific cognitive capabilities that could have evolved from the benefits of having allocentric visual processing.