Memorable objects are more susceptible to forgetting: Evidence for the inhibitory account of retrieval-induced forgetting

Retrieval-induced forgetting with novel visual stimuli is retrieval-specific and strength- independent

Retrieval-induced forgetting (RIF) is the phenomenon whereby remembering a subset of learned items can reduce memory for other related items. There are two main explanations for this effect: the competition account and the inhibition account. Most research to date has favoured the inhibition account, though two potential confounds have been identified in the evidence for key predictions of the account: (1) Using binary measures of accuracy may make it difficult to detect correlations between the magnitude of RIF and the increase in recall for practised items that is predicted by the competition account (strength dependence), and (2) typical non-competitive restudy may be too weak a form of practice to elicit detectible RIF effects. The present study aimed to test these contentions by adapting the RIF paradigm to allow a more graded measurement of memory strength and a more active form of non-competitive practice. We trained participants (N = 87) to draw sets of novel shapes from memory, using colour as a category cue and overlaid patterns as individual item recall cues. Responses were graded based on the number of features present and items underwent retrieval practice, copying practice (as a more effective form of restudy), or no practice. The results demonstrated RIF in the retrieval practice condition, but no evidence of RIF in the restudy condition, despite a large memory gain for practised items, supporting the notion of retrieval specificity. There was no evidence of strength dependence in any condition. Our results are consistent with the forgetting in this experiment being driven by inhibition.

Bizarreness and Typicality Effects of Color on Object Recognition Memory

The bizarreness effect on object recognition is a strong phenomenon, but its influence has been inconsistent for bizarre object color. In this study, we manipulated three factors in separate experiments to determine whether a color bizarreness effect on object recognition memory would occur and, if not, why. Participants first saw (i.e., learned) object pictures that were either bizarrely or typically colored; they then completed a recognition memory test. In three experiments, we then manipulated (a) degree of color bizarreness (Experiment 1), (b) the orientation task (Experiment 2), and (c) additional demands for object identification (Experiment 3). In Experiment 1, we provided 49 undergraduate participants with object pictures whose colors were typical, moderately atypical, or bizarre and found no color bizarreness effect on recognition memory even for extremely bizarre colors. In Experiment 2, we manipulated the orientation task in that 28 young adult participants expressed their preferences for the pictures on a three-point scale while another 28 participants judged how natural the pictures were. Each orientation task group better recognized typically-colored rather than bizarrely-colored objects (typicality effect). In Experiment 3, we asked 27 young adults to identify the objects during the learning phase to ensure that they paid attention to the objects' bizarre colors; recognition memory was then unaffected by either color bizarreness or typicality. Thus, despite a general bizarreness effect in recognition memory, bizarre colors are less likely to influence object recognition memory.

The relative contribution of shape and colour to object memory

The current studies examined the relative contribution of shape and colour in object representations in memory. A great deal of evidence points to the significance of shape in object recognition, with the role of colour being instrumental under certain circumstances. A key but yet unanswered question concerns the contribution of colour relative to shape in mediating retrieval of object representations from memory. Two experiments (N=80) used a new method to probe episodic memory for objects and revealed the relative contribution of colour and shape in recognition memory. Participants viewed pictures of objects from different categories, presented one at a time. During a practice phase, participants performed yes/no recognition with some of the studied objects and their distractors. Unpractised objects shared shape only (Rp–Shape), colour only (Rp–Colour), shape and colour (Rp–Both), or neither shape nor colour (Rp–Neither), with the practised objects. Interference effects in memory between practised and unpractised items were revealed in the forgetting of related unpractised items – retrieval-induced forgetting. Retrieval-induced forgetting was consistently significant for Rp–Shape and Rp–Colour objects. These findings provide converging evidence that colour is an automatically encoded object property, and present new evidence that both shape and colour act simultaneously and effectively to drive retrieval of objects from long-term memory.

What do laboratory-forgetting paradigms tell us about use-inspired forgetting?

Directed forgetting is a laboratory task in which subjects are told to remember some information and forget other information. In directed forgetting tasks, participants are able to exert intentional control over which information they retain in memory and which information they forget. Forgetting in this task appears to be mediated by intentional control of memory states in which executive control mechanisms suppress unwanted information. Recognition-induced forgetting is another laboratory task in which subjects forget information. Recognizing a target memory induces the forgetting of related items stored in memory. Rather than occurring due to volitional control, recognition-induced forgetting is an incidental by-product of activating items in memory. Here we asked whether intentional directed forgetting or unintentional recognition-induced forgetting is a more robust forgetting effect. While there was a correlation between forgetting effects when the same subjects did both tasks, the magnitude of recognition-induced forgetting was larger than the magnitude of directed forgetting. These results point to practical differences in forgetting outcomes between two commonly used laboratory-forgetting paradigms.