On Chapter 4, it covers about how our brain recognizes and conceptualize the world. It talks about that world is not same as we see through the eye. Because in our brain, it always reconstructed the data, we receive from the sensations. Therefore, this chapter talks about which sensory systems in our body can accomplish, and how their physical signal change into neural signal so brain can read the data. This chapter is divided into big four different sections such as the visual system, the auditory system, the sensual senses and touch, body position, and balance. Each sections talks about how physical data transform into neuron so data can deliver to our brain. Although for me the most interesting section was 'the visual system'. There are so many examples about how brain can make illusion. Such as the 'Ponzo illusion' more known as railroad tracks illusion, even there are two same lines in the rail road, but the brain thinks that line in the back is longer than the closer one. In this chapter there is lots of knowledge about sensation that related to our brain.