Separate and joint scaling of perceived odor intensity ofn-butanol and hydrogen sulfide

To determine which combination of scaling method and experimental procedure is optimal for measuring perceived odor intensity, the intensity perception of one odorous substance was scaled both separately and together with a second odorous substance in the same session. The methods used were magnitude estimation with and without a standard reference and cross-modal matching with finger span. The results show that separate and joint scalings ofn-butanol and H₂S give identical scales, regardless of scaling method. Different results are obtained in magnitude estimations with a homoquality, a heteroquality, and no standard. From these results, one would not expect to find a single true power function independent of method. Cross-modal matching with finger span may be the best choice for odor intensity scaling, since it results in the widest response range, thereby giving the best resolution.     

Apparent causality affects perceived simultaneity

The present research addresses the question of how visual predictive information and implied causality affect audio–visual synchrony perception. Previous research has shown a systematic shift in the likelihood of observers to accept audio-leading stimulus pairs as being apparently simultaneous in variants of audio–visual stimulus pairs that differ in (1) the amount of visual predictive information available and (2) the apparent causal relation between the auditory and visual components. An experiment was designed to separate the predictability and causality explanations, and the results indicated that shifts in subjective simultaneity were explained completely by changes in the implied causal relations in the stimuli and that predictability had no added value. Together with earlier findings, these results further indicate that the observed shifts in subjective simultaneity due to causal relations among auditory and visual events do not reflect a mere change in response strategy, but rather result from early multimodal integration processes in event perception.     

An interaction model for odor quality and intensity

The perceived intensity and quality of binary odor mixtures are studied in relation to bow their components are perceived when presented separately. Subjects judged the perceived intensity and quality of 6 concentrations of pyridine, 6 concentrations ofn-butanol, and their 36 possible combinations. The results show that the perceived intensity of the mixture can be predicted from the perceived intensity of its components presented separately (R _A andR _B) by the Euclidian arithmetic model. The maximum probability of identifying a mixture as a “mixture” is reached whenR _A andR _B are equally strong. An interaction model for mixtures that relates perceived intensity and quality is presented and tested. The test reveals that both the perceived intensity of a mixture and the probability that it will be identified as the one or the other component can, by a simple interaction model, be successfully predicted fromR _A andR _B.     

Adrenergic modulation of olfactory bulb circuitry affects odor discrimination

A rodent's survival depends upon its ability to perceive odor cues necessary to guide mate selection, sexual behavior, foraging, territorial formation, and predator avoidance. Arguably, the need to discriminate odor cues in a complex olfactory environment requires a highly adaptable olfactory system. Indeed, it has been proposed that context-dependent modulation of the initial sensory relay could alter olfactory perception. Interestingly, 40% of the adrenergic innervation from the locus coeruleus, fibers that are activated by contextual cues, innervates the first relay station in the olfactory system (the main olfactory bulb). Here we utilize restricted pharmacological inhibition of olfactory bulb noradrenergic receptors in awake-behaving animals. We show that combined blockade of alpha and beta adrenergic receptors does not impair two-odor discrimination behavior per se but does impair the ability to discriminate perceptually similar odors. Thus, contextual cues conveyed by noradrenergic fibers alter processing before the second synapse in the olfactory cortex, resulting in tuning of the ability to discriminate between similar odors.     

Contextual utility affects the perceived quality of explanations

Are explanations of different kinds (formal, mechanistic, teleological) judged differently depending on their contextual utility, defined as the extent to which they support the kinds of inferences required for a given task? We report three studies demonstrating that the perceived “goodness” of an explanation depends on the evaluator’s current task: Explanations receive a relative boost when they support task-relevant inferences, even when all three explanation types are warranted. For example, mechanistic explanations receive higher ratings when participants anticipate making further inferences on the basis of proximate causes than when they anticipate making further inferences on the basis of category membership or functions. These findings shed light on the functions of explanation and support pragmatic and pluralist approaches to explanation.     

Physicochemical characteristics and supraliminal odor intensity: Reply to Mitchell

The rate of growth (exponent) of the psychophysical function for odor intensity depends upon the physicochemical properties of odorous substances. Although no single property is able to predict rate of growth, a model developed by Dravnieks and Laffort that combines three basic properties has been quite successful. The results of intra-O comparisons of the relative exponents for various odorants have withstood the test of replication, i.e., variation among Os has usually not been a serious problem. In the future, comparisons of the exponents obtained from one laboratory to another would be aided considerably by inclusion of a standard odorant in all scaling studies.     

The duration and perceived intensity of sucrose taste

Thirty-two subjects judged the perceived intensity of each of four concentrations of sucrose over 2 min. Stimuli were either sipped and expectorated or flowed over the subject’s extended tongue. Ratio judgments on a line scale and category ratings were made. Sixteen of the subjects had had extensive training in judging the sensory attributes of food products, and another group of 16 subjects were untrained. The perceived intensity of sucrose rose to a peak within 5 or 10 sec, and then declined over 2 min. In both the sip and the flow conditions, the taste disappeared completely for 26 of 32 subjects. Stronger concentrations were perceived as having greater peak intensities and longer lasting taste. The differences between concentrations were enhanced when sipped rather than flowed over the tongue. Judgments of intensity and duration were largely unaffected by the training level of subjects and the use of different rating scales.     

Psychostimulant medication and perceived intensity in hyperactive children

Adult ratings of children's activity, based on impressionistic scales, are good indicators of psychostimulant medication effects. These ratings seldom correlate with objective indicators, however, and their behavioral referents are poorly understood. Two separate studies tested the hypothesis that intensity of child behavior, as perceived by others, would differentiate medicated and unmedicated states. College student subjects assessed randomized videotaped segments of children's behaviors. The perceived intensity of hyperactive children's responses decreased with medication, while there were no medicationrelated changes in either gross motor locomotion or off-task behaviors. In a test for observer sensitization or expectancy, the results for subjects who were looking for medication effects did not differ from those for uninformed subjects.This research was supported in part by NIMH grant 29475 and NIDA grant 01070. We thank Andy Christensen and Carol Whalen for helpful comments.     

Watch this! Observed tool use affects perceived distance

Recent research has shown that being able to interact with an object causes it to be perceived as being closer than objects that cannot be interacted with. In the present study, we examined whether that compression of perceived space would be experienced by people who simply observed such interactions by others with no intention of performing the action themselves. Participants judged the distance to targets after observing an actor reach to an otherwise unreachable target with a tool (Experiment 1) or illuminate a distant target with a laser pointer (Experiment 2). Observing either type of interaction caused a compression of perceived space, revealing that a person’s perception of space can be altered through mere observation. These results indicate that shared representations between an actor and observer are engaged at the perceptual level easily and perhaps automatically, even in the absence of cooperation or an observer’s own intention to interact.     

Temporal context affects the perceived time of visual events

We investigated whether the moment at which an event is perceived depends on its temporal context. Participants learned a mapping between time and space by watching the hand of a clock rotating a full revolution in a fixed duration. Then the hand was removed, and a target disc was flashed within a fixed-interval duration. Participants were to indicate where the hand would have been at the time of the target. In three separate experiments, we estimated the disruption from a distractor disc that was presented before or after the target disc, with a variable time between them. The target was either revealed at the end of the trial or cued beforehand, and in the latter case, was cued by either color or temporal order. We found an attraction to the presentation time of the distractor when both events were attended equally (target revealed at the end). When the target was cued beforehand, the reported time was under- or overestimated, depending on whether the nature of distractor had to be decoded (precued by color) or not (precued by order). In summary, the perceived time of an event is always affected by other events in temporal proximity, but the nature of this effect depends on how each event is attended.

     

The effect of color intensity and appropriateness on color-induced odor enhancement

Coloring solutions has been shown to increase perceived odor intensity. In Experiment 1, subjects rated the odor intensity of red strawberry and green mint solutions that had four levels of color intensity. Ratings of strawberry odor peaked at the medium color intensity and ratings of mint odor increased monotonically with color intensity. Thus, color-induced odor enhancement can increase with increasing color intensity but need not. Experiment 2 found that the color intensities producing maximum odor enhancement in Experiment 1 are not always the ones perceived as most appropriate for the odorants. Using different odors, Experiment 3 found that color intensity has some influence on the strength of the color-induced odor enhancement and color appropriateness has little. The presence or absence of color in the solution seems to be the most important variable.     

Monocular motion adaptation affects the perceived trajectory of stereomotion

Perceived stereomotion trajectory was measured before and after adaptation to lateral motion in the dominant or nondominant eye to assess the relative contributions of 2 cues: changing disparity and interocular velocity difference. Perceived speed for monocular lateral motion and perceived binocular visual direction (BVD) was also assessed. Unlike stereomotion trajectory perception, the BVD of static targets showed an ocular dominance bias, even without adaptation. Adaptation caused equivalent biases in perceived trajectory and monocular motion speed, without significantly affecting perceived BVD. Predictions from monocular motion data closely match trajectory perception data, unlike those from BVD sources. The results suggest that the interocular velocity differences make a significant contribution to stereomotion trajectory perception.     

Surrounding motion affects the perceived locations of moving stimuli

The perceived position of an object is determined not only by the retinal location of the object but also by gaze direction, eye movements, and the motion of the object itself. Recent evidence further suggests that the motion of one object can alter the perceived positions of stationary objects in remote regions of visual space (Whitney & Cavanagh, 2000). This indicates that there is an influence of motion on perceived position, and that this influence can extend over large areas of the visual field. Yet, it remains unclear whether the motion of one object shifts the perceived positions of other moving stimuli. To test this we measured two well-known visual illusions, the Fröhlich effect and representational momentum, in the presence of extraneous surrounding motion. We found that the magnitude of these mislocalizations was altered depending on the direction and speed of the surrounding motion. The results indicate that the positions assigned to stationary and moving objects are affected by motion signals over large areas of space and that both types of stimuli may be assigned positions by a common mechanism.