Enhanced spatial ability in aged dogs following dietary and behavioural enrichment

We examined the benefits of a broad spectrum antioxidant diet and enrichment comprised of physical exercise, environmental stimulants and cognitive testing, on spatial memory performance in beagle dogs. Both aged (N=48) and young (N=16) beagle dogs (Canus familiaris) were tested yearly on a three-component delayed non-match to position spatial task for three consecutive years. The results showed that young enriched animals acquired the task in fewer sessions, made fewer errors, responded slower and made fewer positional responses, compared to aged enriched animals. An analysis restricted to aged animals revealed that antioxidant administration and enrichment resulted in fewer errors, slower responses and decreased positional responses, particularly in Year 3. Finally, cohort differences emerged, which exemplify the significance of early environmental intervention. Aged dogs that were housed with other animals and exposed to an outdoor environment in early development displayed greater benefits from both interventions. These findings indicate that long-term dietary intervention and enrichment can buffer age-associated cognitive decline.     

Susceptibility to induction of long-term depression is associated with impaired memory in aged Fischer 344 rats

The current study employed aged and young male Fischer 344 rats to examine the relationship between long-term depression (LTD), age, and memory. Memory performance was measured on two tasks that are sensitive to hippocampal function; inhibitory avoidance and spatial discrimination on the Morris water maze. The slope of the extracellular excitatory postsynaptic field potential was recorded from CA3-CA1 synapses in hippocampal slices. Low frequency stimulation (LFS) induced a modest LTD only in aged animals under standard recording conditions. The decrease in synaptic transmission examined only in aged animals correlated with memory scores on the spatial task and LTD was not observed in aged animals with the highest memory scores. LTD induction was facilitated by increasing the Ca(2+)/Mg(2+) ratio of the recording medium or employing a paired-pulse stimulation paradigm. Age differences disappeared when LFS was delivered under conditions of elevated Ca(2+)/Mg(2+) in the recording medium. Using multiple induction episodes under conditions which facilitate LTD-induction, no age-related difference was observed in the maximum level of LTD. The results indicate that the increased susceptibility to LTD induction is associated with impaired memory and results from a shift in the induction process. The possible relationship between LTD and memory function is discussed.     

Opposing effects of age and reading ability on pseudoword priming

Repetition priming refers to the facilitation of stimulus processing due to prior processing of the same or similar stimulus, and is one of the most primitive ways in which experience and practice can affect performance. Previous studies have produced contradictory results regarding the stability of repetition priming across development. Drawing on models of word priming that suggest decreased priming with increased reading ability, the present experiment investigated the possibility that null effects of age in priming are due to opposing effects of age and reading ability on priming magnitude. Forty-eight participants between 7 and 22 years old read aloud primed and unprimed pseudowords, after completing a reading ability assessment. In line with predictions, the magnitude of priming for pseudowords increased with increased age when reading ability was controlled, and decreased with increased reading ability when age was controlled. Moreover, neither the age nor ability effect was significant when tested without the other. Results were not influenced by explicit memory for primed pseudowords. Thus, the present experiment provides evidence for developmental increases in word priming, as well as a potential explanation for the lack of developmental effects in previous studies.     

A new dynamical model of brainstorming: Linear, nonlinear, continuous (simultaneous) and impulsive (sequential) cases

In this paper, we extended the linear dynamical model of [Brown, V., Paulus, P. B. (1996). A simple dynamic model of social factors in group brainstorming. Small Group Research, 27, 91-114] on two accounts. First, we modelled the sequential type brainstorming using impulsive differential equations by treating each category as an impulse and tested its validity in the two experiments that investigated and demonstrated the beneficial effects of sequential priming and memory in individual brainstorming. Finally, we considered the nonlinear case of brainstorming in writing or brainwriting where dyads exchanged their ideas in a written format and that eliminated negative factors occurring in oral brainstorming (e.g., evaluation apprehension, free-riding, production blocking) and enhanced the upward performance matching, and conducted the second experiment in order to test its validity in this paradigm with the effects of sequential priming and memory. Comparisons showed good agreement between results of experiments and those of the mathematical model.     

Counterfactual thinking and confidence in blackjack: A test of the counterfactual inflation hypothesis

This research tests the idea that repeatedly generating counterfactual thoughts in response to recurring events can lead to impairments in memory for actual outcomes (i.e., counterfactual inflation hypothesis). Participants (N = 56) played 40 games of blackjack and listed their thoughts after each win. They were instructed to list evaluative counterfactuals, reflective counterfactuals, or any thoughts that came to mind following each loss. Because reflective counterfactuals focus only on the alternatives to reality, and not in addition to reality (like evaluative counterfactuals), they were expected to lead to the greatest degree of overestimations of performance and confidence for future blackjack playing. The results confirmed this hypothesis, and also demonstrated that the relationship between thought-listing instructions and confidence for the future was mediated by overestimations of performance. Thus, repeatedly generating reflective counterfactual thoughts appears to lead to a special case of imagination inflation with dysfunctional implications for future confidence and risk-taking.     

A model of working memory capacity in the radial-arm maze task

The radial arm maze is one of the most commonly used tests for assessing working memory in laboratory animals. However, to date, there exists no quantitative method of estimating working memory capacity from performance on this task. Here, we present a mathematical model of performance on the radial arm maze from which we can derive estimates of capacity. We derive explicit results for the two most commonly used measures of performance as functions of number of arms in the maze and memory capacity, assuming a uniform random search. We simulate random non-uniform search strategies. Comparing our model to previous experiments, we show that our model predicts a working memory capacity in the range of 3-9 at the level of performance observed in these experiments. This estimate is within the typical estimate of human working memory capacity. Performance of rats on large mazes (e.g. 48 arms) has been used as evidence that the working memory capacity of rats may be significantly larger than that of humans. We report that memory capacity in the range 3-9 is sufficient to explain the performance of rats in very large radial mazes. Furthermore, when we simulate non-uniform random search strategies observed in the experiments, the resulting estimates do not differ significantly from those assuming a uniform random search. We conclude that a list-based model of working memory with modest capacity is more powerful than previously expected.     

Sibling differentials in power and memory conformity

How much a person conforms to another person's memory report can depend on the power and credibility of this person, even if these factors are manipulated by the experimenter. The aim of the current study was to establish whether memory conformity is also affected by power in pairs involving natural power differentials, in this case siblings. Pairs of adult siblings were shown 50 photographs of faces and then given a recognition test where one partner had to answer before the other. The findings showed that what one sibling reported affected what the other one reported. Contrary to our expectations, however, there was no significant difference in conformity between the younger and the older sibling. The implications of these findings are discussed.     

Two are better than one: comparison influences infants' visual recognition memory

Despite a large literature on infants’ memory for visually presented stimuli, the processes underlying visual memory are not well understood. Two studies with 4-month-olds (N = 60) examined the effects of providing opportunities for comparison of items on infants’ memory for those items. Experiment 1 revealed that 4-month-olds failed to show evidence of memory for an item presented during familiarization in a standard task (i.e., when only one item was presented during familiarization). In Experiment 2, infants showed robust memory for one of two different items presented during familiarization. Thus, infants’ memory for the distinctive features of individual items was enhanced when they could compare items.     

Voters, Emotions, and Memory

In this paper we argue that emotional response to information encountered in campaigns has implications for the likelihood of remembering that information at the time of the vote. Most voting models are built on what voters remember—whether it is the placement of candidates on issues, or opened ended responses to prompts. That recall of memory is biased is well-known, but the extent to which those biases are driven by affective response to candidate information has not been studied. Using dynamic process tracing, we examine voters' emotional responses, information search, and candidate evaluations during a simulated presidential primary campaign. By manipulating anxiety and the amount of incongruent information that voters encounter, we can detect the direct influence of affect in information processing. We find evidence that voters are more likely to remember information that generates any affective reaction as opposed to information for which the subjects report no emotional response. However, we find little evidence that anxiety has a special role, compared to enthusiasm or anger, in increasing the likelihood that an individual item is remembered. This challenges a primary contention of the theory of Affective Intelligence that anxiety leads to more memories for campaign information.