Effect of stimulus intensity on manual and saccadic reaction time

Reaction time (RT) decreases with stimulus intensity. Hughes and Kesley (1984) demonstrated, however, that the effect of stimulus intensity on simple RT is larger for manual than for saccadic responses. We reexamined this relation under various conditions. The dissociation occurred when the task enabled the generation of exogenous saccades. We found, however, no dissociation if endogenous saccades had to be executed. It is hypothesized that the different effects of intensity result from the simplified neuronal processing of exogenous saccades performed in the direct route from the retina to the superior colliculus.     

Effect of stimulus intensity on lingual vibrotactile fusion thresholds

Lingual fusion thresholds for a two-pulse stimulus were obtained at a 15-dB sensation level and a 35-dB sensation level for 15 subjects (18 to 22 yr.). The 35-dB sensation level provided better temporal resolution thresholds as well as less variable responses.     

A double-response paradigm to study stimulus intensity effects upon the motor system in simple reaction time experiments

A double response paradigm is utilized to study stimulus intensity effects upon the motor system in simple visual and auditory reaction times (RT). Subjects had to respond with both hands simultaneously upon detection of a stimulus. The RT difference of both hands is thereby of special interest, because it is considered that this variable does not contain any sensory latency and therefore allows one to study those processes that follow stimulus detection. It was found that the RT-difference distribution varies with stimulus intensity, which questions the general view that stimulus intensity affects only very early sensory stages in the processing chain. In particular, it was found that the variance of RT difference diminished with increasing stimulus intensity. This finding supports the notion of speeding up the motor process by increasing stimulus intensity. A generalization of a stochastic model by Meijers and Eijkman (1974) and Meijers, Teulings, and Eijkman (1976) is advanced to account for the findings. The central assumption is that more units (e.g., motoneurons) are activated if stimulus intensity is increased. The model’s qualitative predictions are confirmed.     

Latency of the blink reflex and stimulus intensity J

The latency of the eyeblink reflex is inversely related to the intensity of the auditory or visual stimuli used to evoke it. This is true for both mechanical and muscle action potential methods for recording the response.     

Visual acuity and stimulus area

Summary In measuring the distance at which we can observe the fine details of the three stimuli shown in Fig. 3 (striped squares, whose areas are 25, 5 and 1 cm²), we obtain that visual acuity is inversely proportional to the area of the stimulus. Furthermore, visual acuity increases (decreases) in the same way as decreases (increases) the area of the stimulus. This relation should be expressed by an hyperbolic function.

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Zusammenfassung Wenn man den Abstand mißt, aus dem die feinen Einzelheiten der drei gestreiften Quadrate von 25, 5 und 1 cm² in Abb. 3 eben erkennbar sind, ergibt es sich, daß die Sehschärfe umgekehrt proportional der Reizfläche ist, das heißt, daß sie mit zunehmender Reizfläche abnimmt und mit abnehmender zunimmt. Diese Abhängigkeit kann als hyperbolische Funktion dargestellt werden.

     

Consequences of response-contingent change in unconditioned stimulus intensity upon the rabbit (Oryctolagus cuniculus) nictitating membrane response.

In a between-groups design, an instrumental contingency was superimposed on classical conditioning of the rabbit nictitating membrane response. Subjects were exposed to a tonal conditioned stimulus (CS) and, if no conditioned response (CR) occurred, a 5.0-ma. paraorbital electric shock unconditioned stimulus (US). USs of 5.0, 3.3, 1.7, and 0.0 ma., respectively, were contingent on occurrence of a CR in the CS-US interval for subjects in the 4 groups of the experiment. The group exposed to contingent US omission differed from the other 3 groups in percentage CR, onset latency, amplitude, and 2 indices of CR form, and those 3 groups generally did not differ significantly among themselves on these dependent variables. Results were interpreted to be contrary to "law of effect" formulations of classical conditioning.     

Foreperiod and visual stimulus intensity: A reappraisal

The joint effects of stimulus modality, stimulus intensity, and foreperiod on simple RT were investigated. In experiment 1 an interaction was found between stimulus intensity, both visual and auditory, and a variable FP such that the intensity-effect on RT was largest at the shortest FP. Experiment 2 provided a successful replication with smaller and weaker visual stimuli. No interaction was observed with a constant FP, although the visual stimuli were identical and the auditory ones psychophysically equivalent to the visual stimuli of experiment 1.It is proposed that an additive or interactive relationship between stimulus intensity and FP can be inferred only when the mental processes called for by the various uses of FP are simultaneously considered. Another precondition is an adequate sampling of the intensity-continuum with special reference to the retinal size of visual stimuli.     

Reaction time to a second stimulus as a function of intensity of the first stimulus

Reaction time (RT) to the second of two stimuli presented in rapid succession was examined as a function of the intensity of the first stimulus (S₁). It was found that the delay in RT₂ was greater following a dim first stimulus than following a bright first stimulus. The magnitude of this increase corresponded to the difference in RTs to the two intensity levels of S₁. These results support the prediction of a single channel model of response selection. Examination of mean first RTs revealed a general elevation in latency of RT. However, since this increase was not influenced by the inter-stimulus interval (ISI) or by the intensity of the second stimulus (S₂), and since the same increase was found on “catch trials“ where no S₂ was presented, this increase is considered to be a function of change in set in the double response situation.