Weber's Law influences numerical representations in rhesus macaques (Macaca mulatta)

We present the results of two experiments that probe the ability of rhesus macaques to match visual arrays based on number. Three monkeys were first trained on a delayed match-to-sample paradigm (DMTS) to match stimuli on the basis of number and ignore continuous dimensions such as element size, cumulative surface area, and density. Monkeys were then tested in a numerical bisection experiment that required them to indicate whether a sample numerosity was closer to a small or large anchor value. Results indicated that, for two sets of anchor values with the same ratio, the probability of choosing the larger anchor value systematically increased with the sample number and the psychometric functions superimposed. A second experiment employed a numerical DMTS task in which the choice values contained an exact numerical match to the sample and a distracter that varied in number. Both accuracy and reaction time were modulated by the ratio between the correct numerical match and the distracter, as predicted by Weber's Law.     

Creating partially deleted objects for perception research

Line drawings are commonly used in perception research. A basic strategy used in such research is to remove portions of the line drawings in order to determine what features of an object are important for recognition. However, it is important to monitor the amount of contour and type of information that are deleted when one is making partially deleted or fragmented objects. With the Image Fragmenting Program, researchers can use random or manual contour deletion strategies to create fragmented objects while controlling for the amount of contour removed from the images.     

Comparison of behavioral and cognitive-behavioral one-session exposure treatments for small animal phobias

This study evaluated the efficacy of behavioral and cognitive-behavioral one-session exposure treatment procedures with and without programmed generalization for participants with small animal phobias. Forty participants were randomly assigned to the treatment and generalization conditions. Both treatments produced significant improvements from pre-test to post-test and these results were maintained for 1 year. The treatment effect sizes ranged from large to very large across behavioral, self-report, and subjectively rated measures. Participants in the behavioral treatment condition reported that the treatment was significantly more intrusive than participants in the cognitive-behavioral treatment group. The programmed generalization condition did not produce additional measured benefit. The results are discussed in terms of the overall effectiveness of one-session exposure treatment components for small animal phobias.     

The measurement of curiosity as a feeling of deprivation

Curiosity as a feeling of deprivation (CFD) reflects feelings of uncertainty and tension that motivate information-seeking and problem-solving behavior. Twenty-seven CFD items were administered to 321 participants (248 women, 73 men) along with other measures of curiosity and other personality traits such as anxiety, anger, and depression. Factor analyses of the CFD items identified 3 factors from which 5-item subscales were developed: (a) a need to feel competent, (b) intolerance experienced when information is inaccessible or inadequate, and (c) a sense of urgency to solve problems. Moderately high correlations of the CFD scales with other measures of curiosity provided evidence of convergent validity, whereas divergent validity was demonstrated by minimal correlations of the CFD scales with the other personality traits.     

Positive affectivity and lifestyle in adulthood: do you do what you feel?

There is much evidence for the adaptive value of positive affect. Empirical work examining different facets of positive affect and their consequences for psychological adaptation remains sparse, however. This study (young, middle-aged, and older adults; N = 293) investigated the links between two dimensions of positive affect (positive involvement and pleasant affect) and two lifestyles (hedonic and growth related), each indicated by general value orientations, self-reported everyday activities, and activity aspirations. Structural equation models showed that pleasant affect and positive involvement constitute distinct dimensions evincing different age trends and relating differentially to hedonic and growth-related lifestyles. Specifically, pleasant affect, but not positive involvement, was related to a hedonic lifestyle, whereas positive involvement, and not pleasant affect, was associated with a growth-related lifestyle. These findings underline the importance of considering two dimensions of positive affect--pleasant feelings and positive involvement--separately when studying the link between affect and lifestyle.     

College students, tattoos, and sexual activity

This research examined the association of having a tattoo and engaging in premarital sexual intercourse. Data gathered from a convenience sample of 450 college students indicated that tattooed respondents were substantively and significantly more likely to be sexually active than nontattooed college students. Tattooed men became sexually active at a significantly earlier age than nontattooed men but no such difference was found between tattooed and nontattooed college women.     

Involuntary retrieval in alphabet-arithmetic tasks: Task-mixing and task-switching costs

This study explores the effects of memory retrieval in task switching. To this end, item-specific stimulus-to-task mappings were manipulated in two alphabet-arithmetic experiments. Letter-stimuli were presented and the responses were verbal letter names. The task was either to name the next letter in the alphabet, (e.g., C D, task plus), or to name the preceding letter (e.g., C B, task minus). The mapping of individual stimuli to the two tasks (and thus to responses) was either consistent (CM) or varied (VM). In Experiment 1, performance was worse for VM items relative to CM items, indicating item-specific task-mapping effects. These task-mapping effects also contributed to mixing costs (i.e., worse performance in mixed-task blocks than in pure-task blocks) but not to switch costs (worse performance in task-switch trials than in repeat trials within mixed blocks). Experiment 2 manipulated pure and mixed tasks between-participants, and the data again showed differential effects of the task-mapping manipulation on mixing costs and switch costs. This suggests that, in these memory-dependent, alphabet-arithmetic tasks, interference due to involuntary task (and/or response) retrieval primarily increases general multi-task effects, such as maintaining activation of the current task.     

Effects of response selection on the task repetition benefit in task switching

A task switch typically leads to worse performance than a repetition does. This shift cost can be reduced with sufficient task preparation time, but a residual cost usually remains. We propose that a large part of this residual cost is caused by an activation bias produced by response selection processes in the preceding trial. In our experiments, we manipulated response selection requirements using a go/no-go methodology. The residual shift cost disappeared after no-go trials, suggesting that response selection is crucial to establish an activation bias for the current category-response rules and that this bias persists into the next trial. A comparison with a go-only group confirmed this analysis by revealing no differences in preparatory strategy due to the inclusion of no-go trials. In addition, no-go trials had no significant effects on subsequent trials in a single-task experiment, suggesting that no-go trials are not coded as a task different from go trials and that there is no inhibition of the prepared task in a no-go trial. We thus conclude that a persisting activation bias of response rules plays a major role in task switching.     

Linking inhibition to activation in the control of task sequences

Inhibition of abandoned tasks in task switching can be inferred when a worse performance is found withn− 2 task repetitions (ABA sequences) than with nonrepetitions (CBA sequences). Recent evidence has shown that this inhibition effect decreases with long intertrial intervals (i.e., response-cue intervals, RCIs). Two alternatives have been proposed to account for this decrease. One alternative attributes the observed decrease to the decay of inhibition itself. The other alternative proposes that decay of the activation of competing tasks reduces the interference and leads to less inhibition. To decide between these alternatives, we manipulated RCI trialwise. The results favor the decay-of-activation account as an explanation for the decreased inhibition effect. This links the amount of inhibition to the activation level of the competing tasks, whereas evidence for the decay of inhibition remains weak.     

Perception of words and non-words in the upper and lower visual fields

The findings of previous investigations into word perception in the upper and the lower visual field (VF) are variable and may have incurred non-perceptual biases caused by the asymmetric distribution of information within a word, an advantage for saccadic eye-movements to targets in the upper VF and the possibility that stimuli were not projected to the correct retinal locations. The present study used the Reicher-Wheeler task and an eye-tracker to show that, using stringent methodology, a right over left VF advantage is observed for word recognition, but that no differences were found between the upper and the lower VF for either word or non-word recognition. The results are discussed in terms of the neuroanatomy and perceptual abilities of the upper and the lower VF and implications for other studies of letter-string perception in the upper and the lower VF are presented.