What is "verbal overshadowing"

n. (context psychology English) That considering something verbally reduces one's visual or other memory of the thing.

Verbal overshadowing is the negative effect of verbal descriptions upon visual recognition. For example, witnesses who take notes or make verbal descriptions are found to be less able to recognise suspects visually in an identity parade. This effect was originally reported by Jonathan Schooler & Tonya Engster-Schooler (1990) The effect has been found in multiple studies but its strength has varied significantly. A recent international replication effort demonstrated that the effect is quite robust but highly sensitive to changes in the timing parameters. The exact mechanism is not certain and there are several hypotheses. One is that the use of written or verbal language interferes with visual memory. Another is that the process of verbal reasoning changes the level of the criteria which determine recognition.