The current thesis explored the intentional forgetting of different types of facial expression (Angry, Neutral, Happy) within the item-method directed forgetting paradigm (Experiments 1-4). Also, as a manipulation check, Experiment 5 obtained the subjective ratings of valence and arousal for the different types of facial expression used in the previous four Experiments. In summary, a significant directed forgetting effect occurred for Neutral facial expressions; however, a significant directed forgetting effect did not consistently occur for emotional facial expressions (e.g., there was no directed forgetting effect for Angry facial expressions in Experiments 2 and 3, or Happy facial expressions in Experiment 3). These findings are discussed in terms of encoding time as well as valence and arousal, and how these two factors modulate the effect of emotional facial expression on the ability to intentionally forget.

Although forgetfulness is a common and naturally occurring phenomenon, research suggests that it can be intentionally induced using several experimental paradigms. For some individuals, the ability to forget negative thoughts, images, or memories is problematic. That is, the inability to forget may be a source of significant psychological distress (e.g., post-traumatic stress, obsessive-compulsiveness, and depressed mood) that contributes to the maintenance of symptoms of various mental health disorders. The schema-activation hypothesis from Becks (1987) Cognitive Theory of Depression suggest that memories should be more readily brought to mind because they are more readily available through associated activation. Thus, negative memories may be difficult to inhibit (forget), for individuals who are depressed compared to non-depressed counterparts. <p> Indeed, suppression effort (the intentional mental effort to not think about something) often leads to an increase in the very cognitive content targeted for forgetting. For individuals who experience depression or dysphoria, suppression is not effective because the negative cognitive content, which is the hallmark the depressed mood state only serves to maintain or exacerbate the mood state. This raises the question of whether there are alternatives to suppression-like paradigms that may be more efficacious for those who are dysphoric or depressed. Investigating the efficacy of induced-forgetting of negative memories may provide researchers and clinicians with additional avenues to explore the therapeutic potential of induced forgetting as an intervention or preventive strategy in combating depressed mood states. <p>The purpose of the present study was threefold: first, this study examined whether individual differences (e.g., mood state) in a persons ability to call to mind (remember) negative self-relevant memories would affect memory generation time. Second, the implications of differences in mood for the efficacy of two experimental forgetting paradigms Directed Forgetting (DF) and Retrieval Induced Forgetting (RIF) were explored. Finally, individual differences in mental control (i.e., perceived mental controllability, mental control strategies, and rumination as a coping response) were examined in terms of their ability to predict who would be better at remembering and forgetting. <p>University students (N = 103) with high and low levels of symptoms of dysphoria were asked to generate a set of 32 negative memories using cue words. After rating their memories for clarity and negative valance, each set of memories was subject to either a Directed Forgetting or Retrieval-Induced Forgetting procedure. Participants also completed self-report measures of mental control and rumination. Individuals who were dysphoric were similar to those who were non-dysphoric in the amount of time it took to generate a set of 32 negative memories. These results failed to support the tenets of the Schema Activation Hypothesis of Becks (1967) Cognitive Theory of Depression. Subsequent analysis revealed that the act of generating negative memories was mood-inducing, which may have negated the effect of mood on generation time. In terms of the effect of mood on induced-forgetting paradigm efficacy, the analysis yielded several null findings. The insufficient power prohibited the ability to detect small effects. <p>Dysphoric individuals evidenced deficits in forgetting for the directed-forgetting but not the retrieval-induced forgetting paradigm, but only when separate analysis of individual paradigms was undertaken. In this case, the effect of mood on forgetting approached significance for the directed-forgetting paradigm but not the retrieval-induced forgetting paradigm. This suggests that inducing forgetting for those who are dysphoric is more likely to be successful if there is no instruction to forget. Finally, it was predicted that poor perceived mental control, a tendency to ruminate, and the use of mental control strategies would correlate with induced-forgetting. Results suggest that individuals who perceive themselves as poor at controlling mental content, and ruminate about their internal experience of sadness are impaired on recall of negative autobiographic memories when asked to forget them. In contrast, mental control variables were not related to the degree of forgetting using retrieval-practice methodology. The results of this study have implications for future research designed to further explore the therapeutic value of induced-forgetting, particularly for the RIF paradigm. That is, the presence of a retrieval-induced forgetting effect for those who are dysphoric could prove to be a beneficial coping strategy to combat unwanted negative memories. It may be important to study the longitudinal value, as well as explore the potential benefits for other psychologically distressing phenomena in which negative memories are a part (e.g., post-traumatic stress). That cognitive factors, such as mental control and ruminative coping, do not share a relationship with degree of forgetting in the RIF paradigm also bodes well in demonstrating a possible therapeutic advantage for RIF compared to DF. Researchers are advised to consider mood and mental control variables in terms of their potential effects on forgetting paradigm efficacy when selecting their methodology in studies of intentional forgetting. This is particularly important when using a university sample of participants. It is often the case with experimental research, that a university sample is used. Given the higher rates of dysphoria and self-reported depressive symptoms that tend to typify university students and therefore, may be higher than in community-based samples, researchers are cautioned to consider the implications of dysphoria on research outcomes when testing induced-forgetting paradigms.

Although forgetfulness is a common and naturally occurring phenomenon, research suggests that it can be intentionally induced using several experimental paradigms. For some individuals, the ability to forget negative thoughts, images, or memories is problematic. That is, the inability to forget may be a source of significant psychological distress (e.g., post-traumatic stress, obsessive-compulsiveness, and depressed mood) that contributes to the maintenance of symptoms of various mental health disorders. The schema-activation hypothesis from Becks (1987) Cognitive Theory of Depression suggest that memories should be more readily brought to mind because they are more readily available through associated activation. Thus, negative memories may be difficult to inhibit (forget), for individuals who are depressed compared to non-depressed counterparts. <p> Indeed, suppression effort (the intentional mental effort to not think about something) often leads to an increase in the very cognitive content targeted for forgetting. For individuals who experience depression or dysphoria, suppression is not effective because the negative cognitive content, which is the hallmark the depressed mood state only serves to maintain or exacerbate the mood state. This raises the question of whether there are alternatives to suppression-like paradigms that may be more efficacious for those who are dysphoric or depressed. Investigating the efficacy of induced-forgetting of negative memories may provide researchers and clinicians with additional avenues to explore the therapeutic potential of induced forgetting as an intervention or preventive strategy in combating depressed mood states. <p>The purpose of the present study was threefold: first, this study examined whether individual differences (e.g., mood state) in a persons ability to call to mind (remember) negative self-relevant memories would affect memory generation time. Second, the implications of differences in mood for the efficacy of two experimental forgetting paradigms Directed Forgetting (DF) and Retrieval Induced Forgetting (RIF) were explored. Finally, individual differences in mental control (i.e., perceived mental controllability, mental control strategies, and rumination as a coping response) were examined in terms of their ability to predict who would be better at remembering and forgetting. <p>University students (N = 103) with high and low levels of symptoms of dysphoria were asked to generate a set of 32 negative memories using cue words. After rating their memories for clarity and negative valance, each set of memories was subject to either a Directed Forgetting or Retrieval-Induced Forgetting procedure. Participants also completed self-report measures of mental control and rumination. Individuals who were dysphoric were similar to those who were non-dysphoric in the amount of time it took to generate a set of 32 negative memories. These results failed to support the tenets of the Schema Activation Hypothesis of Becks (1967) Cognitive Theory of Depression. Subsequent analysis revealed that the act of generating negative memories was mood-inducing, which may have negated the effect of mood on generation time. In terms of the effect of mood on induced-forgetting paradigm efficacy, the analysis yielded several null findings. The insufficient power prohibited the ability to detect small effects. <p>Dysphoric individuals evidenced deficits in forgetting for the directed-forgetting but not the retrieval-induced forgetting paradigm, but only when separate analysis of individual paradigms was undertaken. In this case, the effect of mood on forgetting approached significance for the directed-forgetting paradigm but not the retrieval-induced forgetting paradigm. This suggests that inducing forgetting for those who are dysphoric is more likely to be successful if there is no instruction to forget. Finally, it was predicted that poor perceived mental control, a tendency to ruminate, and the use of mental control strategies would correlate with induced-forgetting. Results suggest that individuals who perceive themselves as poor at controlling mental content, and ruminate about their internal experience of sadness are impaired on recall of negative autobiographic memories when asked to forget them. In contrast, mental control variables were not related to the degree of forgetting using retrieval-practice methodology. The results of this study have implications for future research designed to further explore the therapeutic value of induced-forgetting, particularly for the RIF paradigm. That is, the presence of a retrieval-induced forgetting effect for those who are dysphoric could prove to be a beneficial coping strategy to combat unwanted negative memories. It may be important to study the longitudinal value, as well as explore the potential benefits for other psychologically distressing phenomena in which negative memories are a part (e.g., post-traumatic stress). That cognitive factors, such as mental control and ruminative coping, do not share a relationship with degree of forgetting in the RIF paradigm also bodes well in demonstrating a possible therapeutic advantage for RIF compared to DF. Researchers are advised to consider mood and mental control variables in terms of their potential effects on forgetting paradigm efficacy when selecting their methodology in studies of intentional forgetting. This is particularly important when using a university sample of participants. It is often the case with experimental research, that a university sample is used. Given the higher rates of dysphoria and self-reported depressive symptoms that tend to typify university students and therefore, may be higher than in community-based samples, researchers are cautioned to consider the implications of dysphoria on research outcomes when testing induced-forgetting paradigms.

Forgetting is an operation which removes information from a set of logical statements, such that a) the language used by the logic is simplified; and b) as much information as possible from the original logical statements are preserved. Forgetting operations are useful in a variety of contexts, including knowledge representation, where it is necessary to have an operation for removing information from knowledge bases; and the problem of relevance, where logical statements are simplified by removing irrelevant information. In this thesis we consider forgetting operations on logic programs with negation-as-failure according to the stable model semantics. There are existing notions of forgetting on logic programs in the literature: the strong forgetting and weak forgetting of Zhang and Foo, and the semantic approach to forgetting introduced by Wang et al. However, these notions are inadequate: the strong and weak forgettings are defined syntactically with no obvious connections to semantic notions of forgetting; while the semantic approach of Wang et al. does not take into account ``hidden'' information encoded in unused rules. The idea of equivalence on logic programs capture the extent of information contained in a logic program. We consider that two logic programs are equivalent iff the two programs contain the same information. For logic programs, there are many different possible notions of equivalence. We look at the well-known notion of strong equivalence and a new notion of equivalence which we call T-equivalence. Associated with each of these equivalences is a consequence relation on logic program rules. We present sound and complete set of inference rules for both consequence relations. We present a novel approach to logic program forgetting which uses as its basis a set of postulates, which are defined relative to a notion of equivalence. We show that if we use T-equivalence as the equivalence relation, then the only possible forgetting operations (up to equivalence) are strong forgetting and weak forgetting. If strong equivalence is used instead, then there are also only two possible forgetting operations (up to equivalence).

Campbell and Phenix (2009) observed retrieval-induced forgetting (RIF) (slower response time) for simple addition facts (e.g., 3 + 4) immediately following 40 retrieval-practice blocks of their multiplication counterparts (3 × 4 = ?). A subsequent single retrieval of the previously unpracticed multiplication problems, however, produced an RIF effect about twice as large for their addition counterparts. Thus, a single retrieval of a multiplication fact appeared to produce much larger RIF of the addition counterpart than did many multiplication retrieval-practice trials. In subsequent similar studies, however, this hyper-RIF effect was not observed (e.g., Campbell & Thompson, 2012). The current studies further investigated hyper-RIF in arithmetic. In Chapter 2 (Experiment 1), composition of operands (unique vs. common) and amount of multiplication practice (6 vs. 20 repetitions of each problem) were manipulated. Participants solved multiplication problems (4 × 7 = ?) and then were tested on their memory for the addition counterparts (4 + 7 = ?) and control additions. Chapter 3 (Experiment 2) attempted an exact replication of Campbell and Phenix. In both studies, hyper-RIF was not observed. The results confirm the basic RIF effect of multiplication retrieval practice on addition counterparts, but cast doubt on the on the reality of the hyper-RIF effect observed by Campbell and Phenix. It is concluded that the hyper-RIF effect reported by Campbell and Phenix is an elusive or non-existent phenomenon; consequently, it cannot at this time be considered an important result in the RIF literature.

In an event-method directed forgetting task, instructions to remember (R) or forget (F) were integrated throughout the presentation of four videos depicting common events (e.g., baking cookies). In a concurrent-instruction paradigm (Experiments 1-5) participants were instructed to remember (R) anything presented when the video border was green and to forget (F) anything presented when the video border was purple. In a post-instruction paradigm (Experiments 6-10) participants were instructed to remember anything preceding a green circle and to forget anything preceding a purple circle. The R or F segments lasted 35 s and were randomly assigned such that each video always contained 4 R and 4 F segments. Participants responded more accurately to cued-recall questions (Experiments 1 and 6) and true-false statements (Experiments 2-5 and 7-10) regarding R segments than F segments although this difference was found only for relatively specific (the woman added 3 cups of flour) as opposed to general (the woman added flour) information (Experiments 5 and 7-10). Participants retain a general representation of the events they intend to forget – even though this representation is not as specific as the representation of events they intend to remember. At encoding, participants were faster to discriminate targets overlaid upon F segments compared to R segments in the concurrent-instruction paradigm (Experiment 3) but were slower to detect targets presented following F compared to R instructions in the post-instruction paradigm (Experiments 6-7 and 9-10). Therefore, whereas both concurrent- and post-instruction paradigms produced comparable effects on subsequent mnemonic performance, the underlying processes are not identical. In the concurrent-instruction paradigm, participants needed to control access to working memory; in the post-instruction paradigm, participants needed to control the contents of working memory. In the former case, we expect that participants minimized processing of F segments while actively rehearsing R segments. In the latter case, we expect that participants engaged one or more active mechanisms associated with the removal of processing resources from the representation of the F segments (functionally terminating rehearsal) while focusing instead on the elaborative rehearsal of the R segments.

Forgetting is an operation which removes information from a set of logical statements, such that a) the language used by the logic is simplified; and b) as much information as possible from the original logical statements are preserved. Forgetting operations are useful in a variety of contexts, including knowledge representation, where it is necessary to have an operation for removing information from knowledge bases; and the problem of relevance, where logical statements are simplified by removing irrelevant information. In this thesis we consider forgetting operations on logic programs with negation-as-failure according to the stable model semantics. There are existing notions of forgetting on logic programs in the literature: the strong forgetting and weak forgetting of Zhang and Foo, and the semantic approach to forgetting introduced by Wang et al. However, these notions are inadequate: the strong and weak forgettings are defined syntactically with no obvious connections to semantic notions of forgetting; while the semantic approach of Wang et al. does not take into account ``hidden'' information encoded in unused rules. The idea of equivalence on logic programs capture the extent of information contained in a logic program. We consider that two logic programs are equivalent iff the two programs contain the same information. For logic programs, there are many different possible notions of equivalence. We look at the well-known notion of strong equivalence and a new notion of equivalence which we call T-equivalence. Associated with each of these equivalences is a consequence relation on logic program rules. We present sound and complete set of inference rules for both consequence relations. We present a novel approach to logic program forgetting which uses as its basis a set of postulates, which are defined relative to a notion of equivalence. We show that if we use T-equivalence as the equivalence relation, then the only possible forgetting operations (up to equivalence) are strong forgetting and weak forgetting. If strong equivalence is used instead, then there are also only two possible forgetting operations (up to equivalence).

I believe art should express things which cannot be easily or entirely explored with words. For me, memory and unconscious mental processes are such matters. Memory is imperfect and impermanent, yet it greatly influences our day-to-day decisions. My memories of fiber art, altered and nostalgic, set me on my path to weaving and the pursuit of fine art. Silent like snowfall: A Retrospective on Memory and Self, explores the memories and concepts behind Silent like snowfall, a woven installation which creates the theoretical space in our minds which houses remnants of memories.

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Attempting to retrieve a target from memory via a retrieval cue can cause competition from the cue's associates, which might block the target. A 1994 study by Anderson, Bjork, and Bjork demonstrated retrieval-induced forgetting for competing associates and suggested that inhibitory control resolving competition causes the forgetting. A 2011 study by Storm, Angello, and Bjork found forgetting for incorrect associates following creative problem solving. This thesis investigated whether such forgetting is also the result of inhibitory control. Competition was manipulated by instructing participants to remember or forget incorrect associates before working on a Remote Associates Test problem. If problem-solving-induced forgetting is caused by inhibition, then to-be-remembered associates should suffer more forgetting than to-be-forgotten associates. Overall, forgetting occurred for incorrect associates participants were instructed to remember and forget. However, the first quartile of trials showed forgetting only for to-be-remembered associates following longer problem solving durations, suggesting a possible role of inhibitory control as an active means to overcome fixation in creative problem solving.