Perceptual selectivity is influenced by different factors. Among them some external factors may be as follows:
- Intensity: High intensity increases the changes of selection. If the message is bright, if sentences are underlined. It gets more attention than in normal case. The greater the intensity of stimulus, the more likely, it will be noticed. An intense stimulus has more power to push itselfto our selection, filters then does the weak stimulus.
- Size: The principle of size says that the larger the object, the more is the probability that is perceived. Size attracts the attention of the individual. A full page spread advertisement attracts more attention than a few lines in a classified section. The reason is not difficult to see. The size establishes dominance and enhances perceptual selection.
- Frequency/Repetition: The repetition principle states that a repeated external stimulus is more attention-getting than a single one. It is for this reason that advertisers go for repetitious advertising to gain the customers' attention to their product.
- Contrast: As per contrast principle, the external stimuli, which stands out against the background will receive more attention. For example, plant safety signs with black lettering or a yellow background or white lettering on a red background are more attention attracting.
- Status: Status held by an individual also influences his/her perception about things or events. Researches suggest that people with high status often exert more influence on the perception of an individual as compared to those holding low status.
- Movement: The movement principle says that people pay more attention to a moving object than the stationery ones. People will be attracted more by a running train than one standing on the platform.