A living object detection system may detect the interaction between an observer and a target object. The system may include an object sensor device, an object classification data unit, and an object detection module. The object sensor device may be attachable to the observer and include an ultrasonic sensor for sensing distance and a passive infrared sensor for sensing temperature. The object classification data unit may store predetermined object classifiers that identifies an object as a living object or non-living object. The object detection module may determine the target object as a living object or a non-living object based on the object classifiers stored in the object classification data unit and on a physical feature set of the target object, where the physical feature set may include distance and temperature parameters.