What is the difference between detection threshold and identification threshold

Cited by links are available to subscribers only. Figure files are available to subscribers only. Article level metrics are available to subscribers only. Allow All Cookies. Not Accessible Your library or personal account may give you access. A 2 , The topics in this list come from the Optics and Photonics Topics applied to this article. Detection and identification: how are they related? Hyperacuity thresholds of 1 sec: theoretical predictions and empirical validation Stanley A.

Model of human visual-motion sensing Andrew B. View More Temporal mechanisms underlying flicker detection and identification for red—green and achromatic stimuli Andrew B. Spatial and temporal parameters of motion detection in the peripheral visual field Jan J.

Previous Article Next Article. References You do not have subscription access to this journal. Cited By You do not have subscription access to this journal. Figures 6 You do not have subscription access to this journal. Metrics You do not have subscription access to this journal. Scott Carney, Editor-in-Chief. Journal Home. Issues in Progress. The spatial phase of grating stimuli was set to give a zero-crossing at the center of the window so as to avoid any artifacts caused by a noninteger number of cycles within the window.

For all experiments we measured thresholds, in logarithmic units, according to a presentation forced choice ZEST Zippy Estimation by Sequential Testing procedure with auditory feedback regarding the correctness of each response.

Subjects responded by means of a button-press. Twelve healthy subjects mean age, All subjects were experienced at performing psychophysical observations and had normal visual fields as determined by the screening program C—1 test of the FDT Perimeter Humphrey Systems; Welch Allyn.

A minimum sample size for experiment 1 was determined by a paired t -test power calculation Lenth RV []; Java Applets for Power and Sample Size [Computer software]. All participants provided informed written consent, and all procedures were carried out in accordance with the tenets of the Declaration of Helsinki and were approved by our institutional ethics committee. Data collection involved two visits within 1 week, with the ordering of tests counterbalanced.

Each visit involved a period of training to ensure subjects fully understood the tests. Experiment 1: Orientation-Identification versus Detection Thresholds. In this experiment we measured detection thresholds for various stimuli and orientation-identification thresholds.

We used a 2-IFC procedure to measure detection thresholds, in which the interval not to be detected was blank. The beginning of each interval was signaled by an auditory tone.

For Gaussian-windowed stimuli, we measured detection thresholds for diagonal gratings only. The final threshold estimate was taken as the arithmetic mean of the individual estimates for a particular location average of four estimates.

Only one type of stimulus or task type detection or orientation identification was used per run. In experiment 2, we investigated the influence of the type of forced-choice methodology used to determine orientation identification thresholds.

For the 2-AFC methodology, we measured thresholds as outlined in experiment 1. Two threshold estimates at each location were obtained per run, with subjects performing 12 runs for each paradigm in an interleaved and counterbalanced fashion. Average thresholds were therefore obtained from 24 threshold estimates per location. One was condition orientation-identification with four detection conditions: horizontal, vertical, oblique, spatially uniform flicker , and the other was test location central, peripheral.

Gaussian stimuli were analyzed separately with a similar RM ANOVA, differing only in the condition orientation-identification, detection within-subjects factor. Experiment 1: Orientation Identification versus Detection Thresholds. Figure 2 shows the mean threshold values for the conditions investigated. All other comparisons were not significant. Figure 3 shows the results for the orientation-identification thresholds measured with 2-IFC and 2-AFC methodologies filled and unfilled symbols, respectively.

The primary aim of this study was to investigate claims that significant differences existed between detection and orientation-identification thresholds for FD stimuli. In doing so, we found no significant differences, consistent with previous findings 9 10 11 20 in healthy subjects. Our results do, however, contrast with the 0. We found no significant effect of eccentricity on the relationship between detection and orientation-identification thresholds Fig.

When measuring pattern detection thresholds with the 2-IFC task, Quaid et al. We found that detection thresholds for a flickering patch were significantly lower than for an FD stimulus Fig. Therefore, these two stimuli should not be used as alternatives in a conventional 2-IFC experiment, especially if they are presented at identical physical contrasts.

If they are, an observer attempting to maximize his or her performance on the task should simply respond to the least visible interval, thereby resulting in a flicker detection threshold rather than an orientation-identification threshold. This threshold would be significantly lower than FD detection thresholds.

It is curious that Quaid et al. It therefore appears that their subjects adopted a suboptimal strategy for performing the task, possibly to ignore the artifact present in their methodology. The influence of subject criteria on such a suboptimal strategy is unknown. Although our testing was performed at a slightly lower luminance than that used by Quaid et al.

We found that horizontal and vertical gratings had similar detectability Fig. Mechanisms Underlying the Frequency-Doubling Phenomenon.

The mechanisms underlying the FD phenomenon are the subject of debate. Maddess and Henry 2 originally suggested that the phenomenon arose from a subpopulation of magnocellular cells within the retina with nonlinear spatial responses M Y cells , though a more recent physiological study 22 has failed to find evidence for such cells in primates and has argued that nonlinear spatial responses cannot generate an FD effect. Evidence also shows that FD targets are detected by the same mechanisms as those that detect spatially uniform flicker.

Rather, such differences likely reflect the operation of a single mechanism showing low-pass spatial tuning and so are in agreement with previous work.

Most studies investigating FD stimuli have used targets presented in a hard-edged window. Our use of a Gaussian-windowed stimulus reduced the magnitude of these high spatial-frequency artifacts by approximately 1 log unit Fig. Despite differences in high spatial-frequency artifacts, we found the relationship between orientation-identification and detection thresholds was identical when hard-edged or Gaussian-windowed targets were used Fig. That optical defocus affects detection and orientation-discrimination thresholds equally for small and large FD targets 16 suggests our findings regarding edge profile generalizes to the smaller low spatial-frequency FD targets used in the new-generation Humphrey Matrix Perimeter.

We found no significant difference between orientation-discrimination thresholds when using an orientation-discrimination paradigm, as described in experiment 1, or a 2-IFC method similar to that of Quaid et al. Should such a difference have been preserved in the 2-AFC task in our orientation-discrimination paradigm, it would have suggested that orientation-identification thresholds should be, if anything, lower than those found in previous studies.

Therefore, the type of forced-choice methodology could not be used as an explanation of why a difference between absolute and orientation-discrimination thresholds was not found in these studies.

The role of attention in the simultaneous-judgment task used by Vallam and Metha 11 is also difficult to quantify. It should be noted, however, that clear changes in threshold can result if methodologies are incorrectly implemented, as we argue is the case in certain experiments reported by Quaid et al. Implications for Frequency-Doubling Technology Perimetry. Despite potentially conflicting results regarding whether frequency doubling is perceived at detection thresholds, a number of clear conclusions emerge from the literature regarding the use of FD gratings in perimetry.

First, evidence indicates that detection and orientation-identification tasks isolate the same mechanism or mechanisms in healthy observers. Second, the relationship between detection and orientation-identification thresholds remains constant regardless of age or the presence of visual field loss from glaucoma, 10 indicating that detection thresholds continue to isolate the same mechanism as orientation-identification thresholds even in the presence of visual field loss. This conclusion holds despite the small methodological differences between the detection and orientation-identification tasks used by McKendrick et al.

Most subjects see FD gratings as close to doubled at orientation-identification thresholds, however, 11 and this is equally true in areas of visual field damaged by glaucoma, 10 consistent with the idea that perceived spatial frequency does not change as a function of suprathreshold contrast level.

This approach is supported by several physiological studies which strongly indicate that the intensity of retronasally perceived odour compounds is highly dependent on the swallowing action Burdach and Doty, ; Land, Buettner and colleagues Buettner and Schieberle, ; Buettner et al.

Using electroglottography, Hodgson et al. These findings support the statement from Burdach and Doty that swallowing plays a role in retronasal odour perception analogous to that played by sniffing in orthonasal perception. Swallowing not only produces a marked retronasal odour transport and perception , but also introduces a temporal dimension to the stimulus delivery. While there is concordant stimulation in time in the Dalton et al.

Thus the sequence of stimuli is taste first and odour second with a time offset dependent on the mode of retronasal transport, i. This offset leads to the question as to whether taste and smell sensations are perceived sufficiently close in time to induce multisensory integration at the neuronal level. In a similar manner to cross-modal processing of visual and auditory inputs Calvert et al.

The present study was designed to progress knowledge on the sub-threshold integration of taste and smell signals reported by Dalton et al. The first experiment aimed to replicate part of the original study to determine if the same enhancement effects could be observed with a different, and larger, panel.

The second objective was to study the effect of asynchronous taste and odour stimuli on the sensory perception to determine whether integration of taste and smell stimuli was dependent on the mode of stimulation. Panellists aged 34—64 years from the University of Nottingham external sensory panel participated in this study. From the 16 original panellists for experiment 1 14 females , 13 panellists 11 females took part in experiment 2. In experiments 3 and 4, 11 9 females and 6 panellists respectively 4 females were selected on the basis of availability and results obtained in experiment 1.

In order to replicate the experiment of Dalton et al. All solutions were prepared in deionized water. Blanks corresponded to samples containing deionized water only. Detection thresholds for taste and smell stimuli were quantified using a two-alternative, forced choice, transformed up-down staircase procedure Wetherill and Levitt, In each trial, a stimulus was paired with a blank and the subjects were instructed to indicate the sample containing the stimulus correct identifications were recorded as an X, incorrect ones as an O.

Presentation order was randomized within pairs. The 3-down, one-up rule rule number 7 Levitt, was selected to target the To determine an appropriate starting concentration, the procedure described by Wetherill and Levitt was adopted. Solutions with decreasing benzaldehyde concentration were presented until an incorrect response was obtained. This concentration defined the starting level for the staircase procedure.

A run is defined as a decreasing or increasing slope between two numbered peaks. Testing stopped after six runs in experiments 1 and 3, and after four runs in experiments 2 and 4 to minimize the volume of liquid ingested and to avoid problems of motivation with the panellists to carry out further experiments. An initial training session was dedicated to familiarize panellists with the odour and the taste stimuli, the test procedure and to aid determination of the appropriate concentration ranges.

The results from these pre-testing sessions were disregarded. All four experiments were conducted in a similar manner; each consisted of three different trials. First, thresholds for benzaldehyde and for saccharin were determined separately for each panellist. The order of presentation, i.

A threshold for benzaldehyde was then obtained a second time in the presence of saccharin at sub-threshold level, although the way in which the stimuli were combined was specific to each experiment Figure 1.

The panellists were instructed to keep their mouth closed during each sample assessment. Total session time was between 2 and 3 h, including 15 min breaks between trials. Summary of protocols used in Experiments 1—4. Saccharin threshold was determined through a sip and spit procedure. For each pair, the panellist was instructed to take all the first sample into the mouth, swirl it around, spit it out, rinse the mouth with deionized water, then perform the same process with the second sample.

Benzaldehyde threshold was obtained by sniffing 50 ml aliquots of odour stimuli or blanks which were presented in wide-necked ml glass bottles sealed with low-odour plastic screw lids. This type of bottle was especially chosen as it allows a close contact of both nostrils with the sample headspace.

It was assumed that this method, by keeping an overall constant flow rate to the nose, would carry a constant olfactory signal to the brain Sobel et al. Panellists were told to open the first sample bottle, sniff the headspace once, put the lid back on to reduce loss of headspace over time, and then proceed to the second sample. The bottles were regularly shaken between presentations to re-establish equilibrium for the volatile in the headspace.

Two sets of bottles were used for each concentration to enable time for equilibrium to be established. The combination of the two stimuli consisted of holding a 10 ml solution of saccharin in a closed mouth whilst sniffing the benzaldehyde sample Figure 1. Panellists rinsed with deionized water after each sample to remove any tastant from the mouth.

No swallowing was allowed during the entire session. Subjects participated in three replicated sessions. As a control experiment, experiment 1 was repeated, except that panellists simply held water, not saccharin solution, in the mouth to rule out the effect of somatosensory cues.

Experiment 2 was performed in the same way as Experiment 1, except that instead of sniffing the benzaldehyde solution, the volatile was delivered in a solution taken orally so that retronasal delivery was achieved.

For each pair, the panellist was instructed to take the first sample in mouth, swirl it around and swallow it, rinse the mouth with deionized water and swallow the liquid to remove potentially lingering volatiles from the pharyngeal part of the tongue. The panellist then assessed the second sample. The swirling served to ensure that the tastant was in contact with taste receptors whereas the swallowing action was crucial to deliver the volatile via the retronasal route Figure 1.

Subjects participated in two replicated sessions. Individual saccharin and benzaldehyde thresholds were determined using the same procedure described in Experiment 1. The combination trial, however, consisted of spitting out the solution of saccharin before sniffing the benzaldehyde sample, to create a temporal delay Figure 1. Timing between the two tasks was especially important and the subjects were therefore told to unscrew but not remove the lid of the benzaldehyde sample while swirling the liquid in their mouths to reduce time between the spit and sniff steps.

Panellists were particularly instructed to keep the delay between steps as consistent as possible. Panellists rinsed after each sample. Double the amount of liquid was chosen to make the combination trial possible in this experiment. The procedure for the combination trial consisted of taking the whole 20 ml sample in the mouth and then swallowing approximately half of the solution to deliver the benzaldehyde retronasally, while keeping the other half in the mouth. This was done to maintain the presence of saccharin on the tongue throughout the experiment Figure 1 and had been practised by the panel prior to the experiment.

The liquid was subsequently expectorated. The data analysis was conducted similarly for the four experiments. For each sequence obtained, the panellist's threshold was obtained by averaging the concentration level at the peaks and valleys Wetherill and Levitt, Ratios, expressed as percentages between benzaldehyde threshold values obtained in the combination condition and obtained individually, were calculated for each panellist replicates.

Threshold means for benzaldehyde alone and in combination with saccharin were calculated. Figure 2 highlights the overall results for experiment 1 which was a repeat of the original Dalton experiment with synchronous taste and orthonasal smell delivery. There were significant differences between the mean threshold values obtained for benzaldehyde alone and in combination with saccharin but for some panellists there was a decrease and for others there was an increase.

For experiment 1 group X represent subjects demonstrating a decrease in threshold. Group Y represents subjects demonstrating an increase in threshold. Numbers in bars indicate number of the panellists. No significant difference in orthonasal benzaldehyde thresholds was observed when holding water in the mouth, ruling out the effect of any other stimuli other than the presence of saccharin. Due to availability, three panellists from the original panel did not take part in this experiment.

Delivery in this experiment was asynchronous with first taste and then retronasal stimulus delivery Figure 1. Figure 2 highlights the overall results and it is notable that detection thresholds were higher when determined retronasally compare with experiment 1.

Only panellists demonstrating an enhancement effect in experiment 1 participated in this experiment. Delivery in this experiment was asynchronous with taste first followed by orthonasal stimulus delivery Figure 1.

Overall results for experiment 3 are highlighted in Figure 2.