Simon Dennis

A Context Noise Model of Episodic Recognition Memory

Item noise models of recognition assert that interference at retrieval is generated by the words from the study list. Context noise models of recognition assert that interference at retrieval is generated by the contexts in which the test word has appeared. The authors introduce the bind cue decide model of episodic memory, a Bayesian context noise model, and demonstrate how it can account for data from the item noise and dual-processing approaches to recognition memory. From the item noise perspective, list strength and list length effects, the mirror effect for word frequency and concreteness, and the effects of the similarity of other words in a list are considered. From the dual-processing perspective, process dissociation data on the effects of length, temporal separation of lists, strength, and diagnosticity of context are examined. The authors conclude that the context noise approach to recognition is a viable alternative to existing approaches.

What is free association and what does it measure

This paper reports the results of a study of free association in which participants were asked to produce the first two words to come to mind. The findings were used to estimate the reliability of indices of strength and set size for different types of items and to model free association as a retrieval task. When confined to first responses, reliability was generally high for both indices, particularly for words with smaller sets of associates and stronger primaries. When second responses were included, reliability declined. A second response added new but weak items to the set, and, when the primary associate was not produced on the first opportunity, it tended not to be produced on the second. Relative to when multiple responses are requested, first-response free association provides more reliable indices of the relative strength and set size for a word’s strongest associates. A model of free association assuming that a strength distribution underlies each response provided a good fit to the data.

Interactive Internet search: keyword, directory and query reformulation mechanisms compared

This article compares search effectiveness when using query-based Internet search (via the Google search engine), directory-based search (via Yahoo) and phrase-based query reformulation assisted search (via the Hyperindex browser) by means of a controlled, user-based experimental study. The focus was to evaluate aspects of the search process. Cognitive load was measured using a secondary digit-monitoring task to quantify the effort of the user in various search states; independent relevance judgements were employed to gauge the quality of the documents accessed during the search process. Time was monitored in various search states. Results indicated the directory-based search does not offer increased relevance over the query-based search (with or without query formulation assistance), and also takes longer. Query reformulation does significantly improve the relevance of the documents through which the user must trawl versus standard query-based internet search. However, the improvement in document relevance comes at the cost of increased search time and increased cognitive load.

Toward a theory of human memory: Data structures and access processes

Starting from Marrs ideas about levels of explanation, a theory of the data structures and access processes in human memory is demonstrated on 10 tasks. Functional characteristics of human memory are captured implementation-independently. Our theory generates a multidimensional task classification subsuming existing classifications such as the distinction between tasks that are implicit versus explicit, data driven versus conceptually driven, and simple associative (two-way bindings) versus higher order (threeway bindings), providing a broad basis for new experiments. The formal language clarifies the binding problem in episodic memory, the role of input pathways in both episodic and semantic (lexical) memory, the importance of the input set in episodic memory, and the ubiquitous calculation of an intersection in theories of episodic and lexical access.

Brief Report: Further Evidence of Sensory Subtypes in Autism

Distinct sensory processing (SP) subtypes in autism have been reported previously. This study sought to replicate the previous findings in an independent sample of thirty children diagnosed with an Autism Spectrum Disorder. Model-based cluster analysis of parent-reported sensory functioning (measured using the Short Sensory Profile) confirmed the triad of sensory subtypes reported earlier. Subtypes were differentiated from each other based on degree of SP dysfunction, taste/smell sensitivity and vestibular/proprioceptive processing. Further elucidation of two of the subtypes was also achieved in this study. Children with a primary pattern of sensory-based inattention could be further described as sensory seekers or non-seekers. Children with a primary pattern of vestibular/proprioceptive dysfunction were also differentiated on movement and tactile sensitivity.

Probabilistic inference in human semantic memory

The idea of viewing human cognition as a rational solution to computational problems posed by the environment has influenced several recent theories of human memory. The first rational models of memory demonstrated that human memory seems to be remarkably well adapted to environmental statistics but made only minimal assumptions about the form of the environmental information represented in memory. Recently, several probabilistic methods for representing the latent semantic structure of language have been developed, drawing on research in computer science, statistics and computational linguistics. These methods provide a means of extending rational models of memory retrieval to linguistic stimuli, and a way to explore the influence of the statistics of language on human memory.

Web searching: a process-oriented experimental study of three interactive search paradigms

This article compares search effectiveness when using query-based Internet search (via the Google search engine), directory-based search (via Yahoo), and phrase-based query reformulation-assisted search (via the Hyperindex browser) by means of a controlled, user-based experimental study. The focus was to evaluate aspects of the search process. Cognitive load was measured using a secondary digit-monitoring task to quantify the effort of the user in various search states; independent relevance judgements were employed to gauge the quality of the documents accessed during the search process and time was monitored as a function of search state. Results indicated directory-based search does not offer increased relevance over the query-based search (with or without query formulation assistance), and also takes longer. Query reformulation does significantly improve the relevance of the documents through which the user must trawl, particularly when the formulation of query terms is more difficult. However, the improvement in document relevance comes at the cost of increased search time, although this difference is quite small when the search is self-terminated. In addition, the advantage of the query reformulation seems to occur as a consequence of providing more discriminating terms rather than by increasing the length of queries.

A Memory-Based Theory of Verbal Cognition.

The syntagmatic paradigmatic model is a distributed, memory-based account of verbal processing. Built on a Bayesian interpretation of string edit theory, it characterizes the control of verbal cognition as the retrieval of sets of syntagmatic and paradigmatic constraints from sequential and relational long-term memory and the resolution of these constraints in working memory. Lexical information is extracted directly from text using a version of the expectation maximization algorithm. In this article, the model is described and then illustrated on a number of phenomena, including sentence processing, semantic categorization and rating, short-term serial recall, and analogical and logical inference. Subsequently, the model is used to answer questions about a corpus of tennis news articles taken from the Internet. The models success demonstrates that it is possible to extract propositional information from naturally occurring text without employing a grammar, defining a set of heuristics, or specifying a priori a set of semantic roles.

Human hippocampus represents space and time during retrieval of real-world memories

Significance The rodent hippocampus contains neurons that code for space on the scale of meters, a discovery that was recently awarded a Nobel Prize. However, it remains unclear whether humans harness similar representations for memory at the scale of their lives. Our results reveal that the human hippocampus represents the spatial and temporal location of memories for real-life events at scales of up to 30 km and a month of time. They further suggest that real-world representations of space and time are more intimately entwined in the hippocampus than previously thought, validating the relevance of decades of rodent studies for human memory and providing a potential mechanism for how we weave the episodic memories of our lives. Memory stretches over a lifetime. In controlled laboratory settings, the hippocampus and other medial temporal lobe brain structures have been shown to represent space and time on the scale of meters and seconds. It remains unclear whether the hippocampus also represents space and time over the longer scales necessary for human episodic memory. We recorded neural activity while participants relived their own experiences, cued by photographs taken with a custom lifelogging device. We found that the left anterior hippocampus represents space and time for a month of remembered events occurring over distances of up to 30 km. Although previous studies have identified similar drifts in representational similarity across space or time over the relatively brief time scales (seconds to minutes) that characterize individual episodic memories, our results provide compelling evidence that a similar pattern of spatiotemporal organization also exists for organizing distinct memories that are distant in space and time. These results further support the emerging view that the anterior, as opposed to posterior, hippocampus integrates distinct experiences, thereby providing a scaffold for encoding and retrieval of autobiographical memories on the scale of our lives.

The Development of Episodic Memory Items, Contexts, and Relations

Episodic memory involves the formation of relational structures that bind information about the stimuli people experience to the contexts in which they experience them. The ability to form and retain such structures may be at the core of the development of episodic memory. In the first experiment reported here, 4- and 7-year-olds were presented with paired-associate learning tasks requiring memory structures of different complexity. A multinomial-processing tree model was applied to estimate the use of different structures in the two age groups. The use of two-way list-context-to-target structures and three-way structures was found to increase between the ages of 4 and 7. Experiment 2 demonstrated that the ability to form increasingly complex relational memory structures develops between the ages of 4 and 7 years and that this development extends well into adulthood. These results have important implications for theories of memory development.