6.1.1 Sensation and perception.

Knowledge is developed through interaction with the material and cultural environments. As we noted the initial processes are mediated by receptor cells for the basic five senses of hearing, vision, smell, touch and taste. All sensation is initiated by some environmental stimulus that carries sufficient energy to excite the nervous system. What we call sensation is the conversion of stimulus energy into neurophysiological processes that create a psychological experience. You taste food from a foreign culture and the sensation may be pleasant or unpleasant dependent on individual preferences and previous sensory experience. However, not all energy that impacts our bodies is brought to our attention. For example some wavelengths are not experienced at all. Our hearing is also limited, whereas dogs possess more acute hearing and smell. The minimum energy required to create a sensation is called the absolute threshold. However, a difference threshold is the minimum change of stimulation required to determine a change in sensation. It is believed that cognition begins with these basic sensory processes.

As we experience the sensory world we gradually build up experience as a reference point for new sensations. Perception involves the organization of association areas in the cortex thereby integrating previous knowledge. Without experience all sensations would be experienced as new and the individual could produce no meaningful pattern from sensory input. Importantly experience creates priming effects as we expect certain feelings associated with past stimuli. Cross-cultural comparisons in the basic areas of sensation and perception show remarkable universal outcomes in various societies pointing to the similarity of the computers we have inherited (Yaroshevski, 1996).

6.1.2 Cultural impact on sensation and perception.

As noted our biological inheritance produces very similar sensation and perception experiences across various cultures. However, as the cultural and material environments differ between societies culture influence perception in some areas. From the outset it is important to understand that there is no one-to-one relationship between physical stimuli and sensation or perception. For example, our brain often fills in and completes sensation where receptors are missing. A case in point is the fact that most of us are not aware of the blind spot in our eyes where no receptors exist in the spot where the optic nerve projects to the brain. The deficit of sensory receptors however, does not cause a deficit in our perception as our brain neatly cover up the lacking information and we experience perception as if we had no blind spot. However, culturally influenced experience can produce illusions for example the famous Mueller-Lyer optical illusion (Segall, Campbell, & Hersokowitz, 1966). Subjects asked to judge two lines of equal length are influenced by whether arrows are pointing toward the line or away with the former line perceived as longer. The most common explanation for cultural affect on this illusionary perception is called the carpentered world theory. Most people in the developed world are accustomed to seeing objects as rectangular in shape with squared corners and not surprisingly Segall et al (1966) found that the optical illusion was stronger in industrialized societies. Further support for cultural influences on perception was found in the research by McGurk and Jahoda (1975) who found that children in different cultures had varying perceptions of spatial relationships. One explanation for cultural differences is that perceptual patterns may be associated with varying rewards that in turn produce preferences. In one study (Broota & Ganguli, 1975) Hindu and Muslim children found punitive stimuli more salient that reward stimuli, whereas children in the U.S. found reward more salient than punishment.

Culture also creates both the presence and absence of certain experiences that in turn affect our ability to perceive the world. The absence of experience has been demonstrated to be a significant factor affecting perception (Blakemore & Cooper, 1970). Cultural groups are exposed to varying environmental conditions salient to perception and experience unique socialization practices that prime perception. Children also learn that certain stimuli are important for adaptation and pay attention to these while ignoring other stimuli less salient. In the long run these varying experiences produce a preference for culturally based sensations and perceptions reflected for example in food or music preferences (Shiraev & Boyd, 2001).