Biomedical subjects

Steven J Haase

Publications and source records attributed to Steven J Haase.

6 recordsLinked to original sources

PubMed2006

Exclusion failure does not demonstrate unconscious perception II: evidence from a forced-choice exclusion task.

Systematic failure to perform exclusion (making a response that opposes the participant's natural inclinations) for briefly displayed, masked words has been interpreted as evidence of unconscious perception. The present study required participants to make a forced-choice exclusion after viewing masked word targets. The forced-choice exclusion task was properly performed in all experiments, in contrast to previous studies that have utilized stem-completion as a dependent variable. The exclusion failure effects interpreted as unconscious perception in earlier studies appear to be caused by an insensitive dependent variable (stem-completion) rather than unconscious perception.

Choice Behavior↗

PubMed2006

Polarity effect in electrovibration for tactile display.

Electrovibration is the tactile sensation of an alternating potential between the human body and a smooth conducing surface when the skin slides over the surface and where the current is too small to stimulate sensory nerves directly. It has been proposed as a high-density tactile display method, for example to display pictographic information to persons who are blind. Previous models for the electrovibration transduction mechanism are based on a parallel-plate capacitor in which the electrostatic force is insensitive to polarity. We present experimental data showing that electrovibratory perceptual sensitivity to positive pulses is less than that for negative or biphasic pulses and propose that this disparity may be due to the asymmetric electrical properties of human skin. We furthermore propose using negative pulses for insulated tactile displays based on electrovibration because their sensory thresholds were found to be more stable than for waveforms incorporating positive pulses.

Adult↗

PubMed2005

Unconscious perception or not? An evaluation of detection and discrimination as indicators of awareness.

Most investigations of unconscious perception use a dissociation design in which an awareness variable (e.g., detection) is compared with a perceptual processing variable (e.g., identification). Unconscious perception is inferred when the awareness variable lacks sensitivity to the stimulus but evidence of perceptual processing is still obtained. In two studies we examined the relationship between word identification and detection (Study 1) or discrimination (words vs. nonwords; Study 2) with a variety of techniques. In both studies, dissociations suggestive of unconscious perception occurred when the data were examined with subjective threshold approaches, but these differences disappeared when the variables were compared with techniques derived from signal detection theory (SDT). These results do not support unconscious perception in subjective threshold paradigms. In addition, detection appears to be the most sensitive and appropriate task for assessing stimulus awareness, provided that several SDT assumptions are met.

Awareness↗

PubMed2004

Valid distinctions between conscious and unconscious perception?

In this commentary, we discuss the strengths and limitations of Snodgrass, Bernat, and Shevrin's (2004) theory of unconscious perception. Our commentary centers on the value of signal detection theory (SDT) to understanding the unconscious perception controversy, a value that Snodgrass et al. for the most part agree with (i.e., that most approaches to studying unconscious perception are invalid because they have confounded the criterion for detection with the criterion for awareness). However, we believe that their model relies on a somewhat restricted application of SDT. We discuss how SDTcan be better applied to provide the necessary tests to validate their model.

Humans↗

PubMed2003

Pattern identification and perceived stimulus quality as a function of stimulation waveform on a fingertip-scanned electrotactile display.

The effect of stimulation waveform on pattern perception was investigated on a 49-point fingertip-scanned electrotactile (electrocutaneous) display. Waveform variables burst frequency (F), number of pulses per burst (NPB), and pulse repetition rate (PRR) were varied in a factorial design. Contrast reduction was used to limit performance of perceiving a 1-tactor gap defined within a 3 x 3 tactor outline square. All three variables accounted for significant variations in performance with higher levels of F and NPB and lower levels of PRR, leading to better performance. In addition, we collected qualitative data on each waveform, and the qualitative differences were related to performance (e.g., waveforms perceived as having a more localized sensation were correlated with better pattern identification performance than those waveforms perceived as more broad). We also investigated the effect of stimulation contrast on pattern perception.

Adult↗

PubMed2003

Pattern identification as a function of stimulation current on a fingertip-scanned electrotactile display.

Two studies were conducted to determine the effect of stimulation current on pattern perception on a 49-point fingertip-scanned electrotactile (electrocutaneous) display. Performance increased monotonically from near chance levels at the lowest sub-threshold current levels tested to approximately 90% at the highest comfortable current levels. This suggests the existence of a tradeoff between spatial performance and usable "gray scale" range in electrotactile presentation of graphical information.

Adult↗