Preference for novel photographs of faces was tested in 5-to 7 -month-old infants following three different proactive interfering conditions that replicated those in which retroactive interference had previously been demonstrated by Fagan (1973). One group of infants was presented with three successive presentations of upside-down caricatures of faces prior to the familiarization and novelty test, whereas the other two groups experienced three successive presentations of either upside-down or upright photographs of faces. Consistent with demonstrations of retroactive interference, preference for novelty existed following presentation of the rotated caricatures but not following rotated photographs. However, contrary to the effects due to retroaction, upright photographs did not lead to a preference for novelty. This differential disruption of preference for novelty is discussed as indicating either the existence of proactive interference in which the effects of perceptual similarity are different from those of retroaction, or the presence of a differential release from proactive interference that does not operate in retroaction.Using the paired-comparison test of preference for novelty, Fagan (1970Fagan ( , 1973 demonstrated that infant recognition memory is quite robust, lasting over a period of 2 weeks following a 2-min exposure to a to-beremembered stimulus. Furthermore, he demonstrated several parallels between infant and adult memory phenomena, including differential forgetting due to retroactive interference and the elimination of interference effects if the presentation of the interfering event was delayed for 3 h following the initial recognition test-an effect consistent with the consolidation theory proposed by Hebb in 1949.Directly relevant to the current investigation was Fagan's demonstration that delayed recognition of photographs of human faces by 21-to 25-week-old infants was disrupted by presentation of upside-down photographs of similar faces following the initial familiarization period. However, disruption was not created by upside-down line drawings of faces or by presentation of upright photographs of similar faces. He hypothesized that this pattern of differential disruption indicated interference related to the degree of perceptual similarity between the photographs employed in the test of preference for novelty and the interfering stimuli-with the line drawings being less Copyright 1990 Psychonomic Society, Inc. similar than rotated photographs, and the upright photographs being highly similar. This interpretation is consistent with the Skaggs-Robinson hypothesis (Robinson, 1927) of interference in adult recall, in which interference varies as a function of stimulus similarity.In the present experiment, we investigated differential disruption of memory in infants in a procedure analogous to that which produces proactive interference in adults (Underwood, 1957;Whitely, 1936). We reasoned that if memory in human infants is analogous to memory in older children and adults, then proactive int...