Which transformations of stimuli are the most disruptive to facial recognition?

In the literature on face recognition, there is a considerable volume of da ta indicating that transforming a face between a familiarization procedure and recognition testing impairs performance. As many: different tyres nf tr ansformations have been shown to produce this effect, it seems tempting to assume that any type of transformation can lead to this performance decreme nt. However to date, there have been no systematic attempts to identify whi ch transformations produce the most impairment in facial recognition. There fore, an experiment was conducted in which subjects viewed facial stimuli d uring the familiarization phase and were then required to perform a memory test with either transformed or unaltered stimuli. The transformations exam ined in this experiment were a disguise (the addition of sunglasses), later al reversal and inversion. Results suggest that inversion produced the larg est decrease in recognition, and the addition of a disguise or lateral reve rsal of the stimuli produced similar, but smaller, detrimental effects.