If presented with a novel and a familiar object, infants strongly prefer to touch and look at novel objects. However, if these objects are then obscured – in the dark, or by an occluding screen – infants tend to reach more in the direction of the familiar objects. Some argue that the familiar objects are represented more strongly by neural networks, whereas the relatively weaker representations of novel objects are more likely to decay in the absence of sensory input, and thus less likely to motivate an infant’s reach.
Similar mechanisms may exist in adults. A review of the literature suggests that familiarity enhances “detection” across an enormous variety of ages, tasks and contexts.
For example, in their 2003 article, Buttle & Raymond review evidence showing that highly familiar words are not subject to the attentional blink effect (a phenomenon in which the second of two rapidly-presented target stimuli cannot be detected). Likewise, subjects are more likely to detect the repetition of a familiar stimulus than an unfamiliar stimulus (i.e., a reduced repetition blindness effect). Finally, visual search is known to be more efficient for familiar than unfamiliar targets (i.e., an upright “2″ is discovered faster than a rotated “2″.)
Buttle & Raymond themselves made a similar discovery. Subjects were faster to detect changes in familiar than less familiar faces, suggesting again that familiarity improves neural processing efficiency.
There are two reasons to believe this familiarity benefit is limited to configural or holistic processing of faces, as opposed to featural processing. First, the familiarity effect was limited to faces presented on the left hemifield; information presented on this side of the visual field is routed to the right hemisphere, which is known to be involved in configurational, relational, and holistic processing. Secondly, the familiarity effect was abolished altogether if inverted faces were used. Configurational face processing is disrupted by the use of inverted relative to upright faces (see here to experience this yourself).
In addition to this standard familiarity effect, subjects were also more accurate to detect changes of any kind if the non-chaning face was highly familiar. In a 2006 study, Chen et al report something similar: subjects were better to detect changes in a display where a familiar but abstract visual shape remained unchanged*. According to Buttle & Raymond, this probably results from subjects more quickly processing the familiar object, thus more quickly realizing that it had not changed, and therefore more quickly allocating attention to the other part of the display.
Jacobsen et al. cover similar ground in the auditory domain. First, consider that scalp electrical activity sharply decreases in voltage when subjects encounter an unexpected sound (this is known as “mismatch negativity”). It turns out that less “deviant” sounds are required to elicit the same amount of mismatch negativity when that sound is embedded in a sequence of familiar sounds, relative to embedding in a sequence of unfamiliar sounds. Similarly, Jacobsen et al. found increased mismatch negativity when deviant sounds are embedded in sequences of familiar relative to unfamiliar sounds.
In summary, “some things never change” when it comes to developmental cognitive neuroscience: across the lifespan, the neural representations of familiar objects seem more durable, easier to activate/process, and easier to maintain than the representations of less familiar objects.
* – Note that Chen et al. did not find overall benefits for familiar objects in change detection. However, this result is probably due to methodological differences; unlike the other studies reported here, Chen et al. compared accuracy on a condition where familiar objects changed into other familiar objects relative to a condition where unfamiliar objects changed into other unfamiliar objects.