How contrast affects stereoacuity

Stereoacuity and its dependence on contrast were measured at four spatial frequencies separated by 1 octave steps. Using a method of adjustment, observers adjusted the retinal disparity of an aperiodic narrow-band stimulus until it appeared in the depth plane defined by two flanking reference lines. Variations in contrast affected stereoacuity (the standard deviation of ten depth settings), with better performance observed at higher contrasts. Data were fit with straight lines (on a log-log plot), indicating a power-law dependence on contrast; the slope was steeper at lower spatial frequencies. These findings are consistent with the idea that disparity is computed from the responses of size-tuned mechanisms characterized by nonlinear contrast transfer functions. In a second experiment, the effects of interocular differences in contrast on stereoacuity were studied for two conditions. In the first condition, one eye always viewed a high-contrast target while the other eye viewed targets of successively lower contrast; in the second condition, one eye always saw a target of near-threshold contrast while the other eye saw targets of successively higher contrast. When the fixed contrast was high, stereoacuity deteriorated steadily as the interocular difference in contrast increased; the loss of stereoacuity was greatest at the lowest spatial frequency. When the fixed contrast was low, however, small increases in the contrast to one eye had no deleterious effect on stereoacuity. Once interocular contrast settings exceeded a certain difference, stereoscopic acuity began to deteriorate at lower spatial frequencies. These results address the issue of the stage of visual processing at which contrast exerts its influence on stereopsis.     

The Macintosh as a user-friendly laboratory for perception and cognition

We present a radically user-friendly Macintosh laboratory, MindLab, for instruction in perception and cognition. MindLab’s forte is its ability to display pictorial stimuli, including digitized photographs, transferred via the clipboard from Macintosh graphics applications. An experiment is programmed by specifying sequences of event primitives, represented by icons, to which stimuli, temporal parameters, and feedback options are assigned.     

Uncertainty impairs grating detection performance in the cat

Using behavioral techniques, contrast thresholds for detection of grating patterns by the cat were measured under conditions of certainty and uncertainty. For certainty trials, the same combination of spatial and temporal frequencies was presented throughout a test session, whereas with uncertainty, the cat was unable to anticipate which of two spatial (or temporal) frequencies would be presented on a given trial. For most spatiotemporal combinations, uncertainty served to elevate contrast thresholds by almost .3 log units, a finding that parallels the outcome found in human vision. The uncertainty paradigm may provide a useful inferential tool for determining channel bandwidth in cat vision.     

Perceptual Priming by Invisible Motion

When observers see motion that is not really there, they can nonetheless show evidence of motion priming. And when observers do not see motion that is really there, they also show evidence for motion priming. Evidently, the process responsible for establishing motion correspondence is sensitive to contextual information, and this sensitivity is modulated at preconscious levels of visual analysis.     

Contextualizing Gender and Acculturative Influences on Sexual Initiation of Asian Indian Emerging Adults

Although Asian Indians represent one the fastest growing demographics in the United States, no studies exist on the sexual behavior of Asian Indian youth or its association with acculturation. Previous research has demonstrated a link between earlier sexual initiation and subsequent sexual risk and the role of acculturation and sexual initiation in other Asian groups. The present exploratory study examined gender and acculturation with regard to sexual initiation in Asian Indians (n = 37). Results reveal no significant gender differences in sexual initiation and total acculturation scores. Gender differences did emerge for the association among sexual behaviors and the influence of specific areas of acculturation on sexual initiation. Findings suggest that gender and acculturation may be important variables in understanding sexual behavior but that current acculturation measures may be insufficient to adequately assess acculturation levels of Asian Indian youth. Future research should focus on Asian Indians as an understudied minority group.     

Development and evaluation of a scale assessing therapist fidelity to guidelines for delivering therapist-assisted Internet-delivered cognitive behaviour therapy

Internet-delivered cognitive behaviour therapy (ICBT) is often accompanied by therapist emails, but there is limited research on the quality of this therapist-assistance. In this study, an ICBT Therapist Rating Scale (ICBT-TRS) was developed and evaluated to assess whether therapist emails showed fidelity to specific therapist behaviours. Using data from a previous ICBT trial for depression and anxiety, the ICBT-TRS was used to rate 706 emails sent by 39 therapists to 91 randomly selected patients. Emails were rated for adherence (absent/present) and quality (inadequate/competent) on the following behaviours: Builds Rapport, Seeks Feedback, Provides Symptom Feedback, Provides Psychoeducation, Facilitates Understanding, Praises Effort, Encourages Practice, Clarifies Administrative Procedures, and Communicates Effectively. Inter-rater reliability was high. Most behaviours were identified as present in 72–100% of emails, with the exception of Provides Symptom Feedback and Facilitating Understanding which were only present in 54 and 61% of emails. The majority of emails were rated as high quality (88–98% of messages). While not related to symptom improvement, ICBT-TRS ratings were higher when patients were more engaged in ICBT (e.g. log-ins) and among therapists who specialized in ICBT or had a background in Psychology. The ICBT-TRS has potential to facilitate ICBT research and clinical training.     

The relationship between therapeutic engagement,cognitive errors,and coping action patterns: An exploratory study

Aim: This exploratory study examined the relationship between clients’ involvement in therapy and their cognitive errors (CE) and coping action patterns (CAP). Method: Therapy sessions from N = 26 clients were rated for CE and CP using the CE and CAP methods. Client involvement was measured with the Positive and Negative Affect Schedule, as well as the . Results: The CEs’ ‘magnification of the negative or minimisation of the positive’ and ‘labelling’ were associated with measures of affective therapeutic engagement. The coping styles ‘negotiation’, ‘opposition’, ‘submission’, ‘isolation’, ‘support seeking’, ‘information seeking’, ‘delegation’, and ‘escape’ were found to be associated with affective and behavioural dimensions of therapeutic involvement. Conclusions: These findings provide preliminary supporting evidence that CE and CP are related to the extent to which clients engage in the work of therapy. Implications for researchers and therapists are discussed.     

Pattern and flicker detection examined in terms of the nasal-temporal division of the retina

Contrast thresholds for the detection of flicker and the detection of pattern were measured for nasal and temporal retinae of each eye separately. While confirming that these two types of threholds can differ, depending on the spatial frequency, the results provide no support for hemiretinal or hemispheric asymmetries in the distribution of the putative pattern and movement channels.     

On assessing individual differences in rumination on sadness

The Rumination on Sadness Scale (RSS), an individual-difference measure of rumination on sadness, was developed as an alternative to the Ruminative Responses scale of the Response Styles Questionnaire (RRRSQ; Nolen-Hoeksema & Morrow, 1991). Research has shown the RRRSQ to consist of multiple, not highly intercorrelated factors; only I factor explicitly addresses rumination. In Study 1, a 1-factor solution to a principal components analysis was shown to hold for responses to the RSS. The RSS was also shown to be reliable. In Study 2, convergent and discriminant validity of the RSS were assessed. In Study 3, individuals with high RSS scores exhibited more distress regarding current concerns with the introduction of a delay period (to allow them to ruminate) after a sad mood induction.