Jonathan Schooler who discovered that talking about a problem interfered with problem solving by insight. Verbal mediation does not worsen all types of problem solving of course - in older adults, in fact, researchers found that having older adults talk aloud while solving Raven's matrices increased their IQ performance by 11 points.
But verbal overshadowing is a real phenomenon, and another example of counteracting processes of words and images in the brain.
Verbal overshadowing refers to the process by which putting experiences into words can certain aspects of visual and other perceptual memories.
- After viewing a video of a bank robbery, subjects were 64% accurate picking the robber from a line if they relied on vision alone, but only 38% accurate if they gave a verbal description of the robber before searching the lineup.
- After viewing a map with landmarks, only those subjects who had been asked to verbally describe the map had trouble estimating the distances between landmarks. The thought is that words interfered with the spatial image of the map.
- After listening to a spoken phrase, test subjects who were asked to write down everything they heard had a harder time identifying the voice that was used
More recent information about the verbal mediation suggests that individuals with stronger spatial ability are more susceptible to the verbal overshadowing effect...so that means that spatial thinkers may really not want to solve problems with words because it may disrupt their spatial processing and cause them to make more mistakes. In most of the students we see in the clinic where verbal mediation helps, their imagery for the task is weak (like dyslexic students verbalizing spelling words) - so this all makes sense.
In the figure at left, Melcher (2004) found that perceptual training increased the verbal overshadowing effect (in this experiment, subjects were trained on visual discrimination of different mushroom types).
Take-home point for teachers: when we're teaching or demonstrating a lesson, we should be attuned to primary modality we're trying to entrain. Sometimes we need to show and talk less.
Also if our students are spatial experts, we should understand why they don't like to "show their work" and not have it required of them.
Verbal Overshadowing of Spatial Mental Models
Verbal Overshadowing Articles