Virtual human analogs to rodent spatial pattern separation and completion memory tasks

Spatial pattern separation (SPS) and spatial pattern completion (SPC) have played an increasingly important role in computational and rodent literatures as processes underlying associative memory. SPS and SPC are complementary processes, allowing the formation of unique representations and the reconstruction of complete spatial environments based on partial spatial information. We present two novel computerized navigational tasks as human analogs of well-established rat SPS and SPC tasks. Results from these tasks show that human participants are sensitive to increasing SPS and SPC demands. Specifically, memory accuracy decreased with decreasing separation distance between target and foil locations in the SPS task and with decreasing number of distal spatial cues in the SPC task. These tasks set the stage for valuable future directions, including the use of these tasks with imaging and clinical populations.     

Intraclass correlation associated with therapists: estimates and applications in planning psychotherapy research

It is essential that outcome research permit clear conclusions to be drawn about the efficacy of interventions. The common practice of nesting therapists within conditions can pose important methodological challenges that affect interpretation, particularly if the study is not powered to account for the nested design. An obstacle to the optimal design of these studies is the lack of data about the intraclass correlation coefficient (ICC), which measures the statistical dependencies introduced by nesting. To begin the development of a public database of ICC estimates, the authors investigated ICCs for a variety outcomes reported in 20 psychotherapy outcome studies. The magnitude of the 495 ICC estimates varied widely across measures and studies. The authors provide recommendations regarding how to select and aggregate ICC estimates for power calculations and show how researchers can use ICC estimates to choose the number of patients and therapists that will optimize power. Attention to these recommendations will strengthen the validity of inferences drawn from psychotherapy studies that nest therapists within conditions.     

Comparison of age and time-to-death in the dedifferentiation of late-life cognitive abilities

The dedifferentiation hypothesis proposes that specific cognitive abilities become more highly associated with general ability in old age as a result of increasing biological constraints on fluid intelligence. There is limited evidence for the hypothesis, and research has not tended to clearly distinguish age dedifferentiation from ability differentiation and other age-related phenomena. The present study examined age dedifferentiation using a structural equation model that controlled for ability differentiation, along with linear and quadratic effects of age. Time-to-death was examined as an alternative time metric to chronological age, as it may better represent biological constraints. The Canberra Longitudinal Study community-based cohort, consisting of 896 Australian adults aged 70 and over, provided data from 687 decedents who were followed for up to 17 years. Results indicated little support for the age dedifferentiation hypothesis, with only two of seven cognitive tests showing significant age dedifferentiation. The time-to-death metric showed more evidence of dedifferentiation, with four of the seven tests exhibiting dedifferentiation. However, after excluding participants with possible cognitive impairment, all of the dedifferentiation effects were attenuated to nonsignificance. Age dedifferentiation effects may therefore reflect dementia and other mortality-related pathology rather than being an inevitable outcome of advanced age. Alternative developmental theories for cognitive function must better account for the diversity of late-life abilities and pathology.     

The effect of education on the onset and rate of terminal decline

Differences in the time of onset and magnitude of terminal decline were examined in three cognitive domains: processing speed, episodic memory, and global function. In addition, cognitive reserve was investigated by testing whether education affected the onset or rate of decline across these domains. Eight hundred ninety-six community-dwelling Australian adults aged ≥ 70 years were assessed up to four times over 12 years, with vital status followed for 17 years. For each of the cognitive measures, a series of change point models were fitted across the 20 years before death to find the optimal point at which terminal decline was distinguished from preterminal decline. Change points were then assessed separately for high- and low-education groups. The change points were 8.5 years for processing speed (95% CI: 6.0-11.2 years), 7.1 years for global function (6.2-9.3), and 6.6 years for episodic memory (5.3-7.1). The rate of decline was two to four times greater in the terminal phase relative to the preterminal phase, depending on the domain. Increased education changed the terminal decline effect differently for each of the three tests, either by significantly hastening the onset of terminal decline and decreasing the rate of decline, or by increasing the rate of either preterminal or terminal decline. Analyses were repeated excluding participants diagnosed with dementia, with no substantive change to the outcomes. In conclusion, the rate and onset of terminal decline varied somewhat across cognitive domains. Education affected terminal decline differently across the domains, but this modification was not consistent with the predictions of cognitive reserve theory.     

Neural theory for the perception of causal actions

The efficient prediction of the behavior of others requires the recognition of their actions and an understanding of their action goals. In humans, this process is fast and extremely robust, as demonstrated by classical experiments showing that human observers reliably judge causal relationships and attribute interactive social behavior to strongly simplified stimuli consisting of simple moving geometrical shapes. While psychophysical experiments have identified critical visual features that determine the perception of causality and agency from such stimuli, the underlying detailed neural mechanisms remain largely unclear, and it is an open question why humans developed this advanced visual capability at all. We created pairs of naturalistic and abstract stimuli of hand actions that were exactly matched in terms of their motion parameters. We show that varying critical stimulus parameters for both stimulus types leads to very similar modulations of the perception of causality. However, the additional form information about the hand shape and its relationship with the object supports more fine-grained distinctions for the naturalistic stimuli. Moreover, we show that a physiologically plausible model for the recognition of goal-directed hand actions reproduces the observed dependencies of causality perception on critical stimulus parameters. These results support the hypothesis that selectivity for abstract action stimuli might emerge from the same neural mechanisms that underlie the visual processing of natural goal-directed action stimuli. Furthermore, the model proposes specific detailed neural circuits underlying this visual function, which can be evaluated in future experiments.     

Reallocating attention during multiple object tracking

Wolfe, Place, and Horowitz (Psychonomic Bulletin & Review 14:344?C349, 2007) found that participants were relatively unaffected by selecting and deselecting targets while performing a multiple object tracking task, such that maintaining tracking was possible for longer durations than the few seconds typically studied. Though this result was generally consistent with other findings on tracking duration (Franconeri, Jonathon, & Scimeca Psychological Science 21:920?C925, 2010), it was inconsistent with research involving cuing paradigms, specifically precues (Pylyshyn & Annan Spatial Vision 19:485?C504, 2006). In the present research, we broke down the addition and removal of targets into separate conditions and incorporated a simple performance model to evaluate the costs associated with the selection and deselection of moving targets. Across three experiments, we demonstrated evidence against a cost being associated with any shift in attention, but rather that varying the type of cue used for target deselection produces no additional cost to performance and that hysteresis effects are not induced by a reduction in tracking load.     

Etchemendy on Squeezing Arguments and Logical Consequence: a Reply to Griffiths

Owen Griffiths has recently argued that Etchemendy’s account of logical consequence faces a dilemma. Etchemendy claims that we can be sure that his account does not overgenerate, but that we should expect it to undergenerate. Griffiths argues that if we define the relationship between formal and natural language as being dependent on logical consequence, then Etchemendy’s claims are not true; and if we define the relationship as being independent of logical consequence, then we cannot assess the truth of the claims without further information. I argue that Griffiths misconstrues Etchemendy’s theory and overstates the first horn of the dilemma: Etchemendy does see the relationship as being dependent on logical consequence, but that does not mean that his claims are not true.     

Exploring the psychometric properties of the CES-D-10 and its practicality in detecting depressive symptomatology in 27 low- and middle-income countries

The Center for Epidemiological Studies Depression-10 (CES-D-10) scale is known for its good psychometric properties in measuring depressive symptoms, however, some researchers question its applicability across various settings. This study explored the factor structure of the CES-D-10 in low- and middle-income countries (LMICs). This cross-sectional survey consisted of 16,723 university students across 27 LMICs that completed self-report instruments assessing socio-demographic information and depressive symptoms using the CES-D-10. Data analysis included: exploratory factor analysis, item response theory and differential item functioning. Results indicate that a two-factor model (depressive affect and positive affect) had the best fit for this population and accounted for 52% of the total observed variance with an internal consistency, α = .77 for the depressive affect items and α = .57 for the positive affect items. The graded response model (GRM), however, indicated that the depressive affect factor had a good fit, unlike the positive affect factor. The depressive affect factor was found to consistently model depression for females better than males. Relative to their Asian counterparts, African, Caribbean and South American participants of similar depressive affect responded differently on all items of the depressive affect factor. The depressive affect factor seems most ideal for LMICs and shows gender and cross-cultural variability.     

Profile of cognitive deficits and associations with depressive symptoms and intelligence in chronic early‐onset schizophrenia patients

Cognitive deficits in several domains have been demonstrated in early‐onset schizophrenia patients but their profile and relation to depressive symptoms and intelligence need further characterization. The purpose was to characterize the profile of cognitive deficits in chronic, early‐onset schizophrenia patients, assess the potential associations with depressive symptom severity, and examine whether cognitive deficits within several domains reflect intelligence impairments. This study compared attention, visual‐construction, aspects of visual and verbal memory, and executive functions in chronic, early‐onset schizophrenia patients (mean age = 20.7 years) (N = 18) and healthy controls (N = 38). Schizophrenia diagnoses were established at the time of the patients' first clinical presentation during childhood or adolescence and were confirmed five years later. In the chronic phase of early‐onset schizophrenia, significant deficits were observed in all specific cognitive functions. The profile of cognitive deficits was jagged, and visual‐construction, attention, and one aspect of verbal memory (verbal stories recall) were differentially impaired. Deficits of visual recall, visual recognition, and executive functions were accounted for by deficits in intelligence, while this was not the case for deficits of verbal recall of stories or attention. No significant associations were observed between the severity of cognitive deficits and that of depressive symptoms. Chronic, early‐onset schizophrenia is characterized by a broad and jagged profile of cognitive deficits. Deficits of attention and verbal recall of stories appear not to be accounted for by deficits in intelligence, and the severity of cognitive deficits seems independent from that of depressive symptoms     

The Incan Quipus

Quipus, knotted structures of woollen or cotton cords, were used as a bureaucratic tool in the Inca state. In the absense of a writing system, numerals and possibly other pieces of information were encoded on the quipus by tying knots into elaborately structured coloured cords. Though interpretation of the quipu contents is far from complete, some information on Inca mathematics can be deducted from the analysis of ancient specimen, especially when combined with the results of anthropological and linguistic research in contemporary Andean societies. In this paper, the quipus are introduced, their structure is explained, and some results on mathematical concepts of the Incas are presented based on a comparison of mathematical and anthropological literature on the subject.