Information transmission with a multifinger tactual display

In this work, the tactual information transmission capabilities of a tactual display designed to provide stimulation along a continuum from kinesthetic movements to cutaneous vibrations are assessed. The display is capable of delivering arbitrary waveforms to three digits (thumb, index, and middle finger) within an amplitude range from absolute detection threshold to about 50 dB sensation level and a frequency range from dc to above 300 Hz. Stimulus sets were designed at each of three signal durations (125, 250, and 500 msec) by combining salient attributes, such as frequency (further divided into low, middle, and high regions), amplitude, direction of motion, and finger location. Estimated static information transfer (IT) was 6.5 bits at 500 mseC., 6.4 bits at 250 mseC., and 5.6 bits at 125 msec. Estimates of IT rate were derived from identification experiments in which the subject’s task was to identify the middle stimulus in a sequence of three stimuli randomly selected from a given stimulus set. On the basis of the extrapolations from these IT measurements to continuous streams, the IT rate was estimated to be about 12 bits/seC., which is roughly the same as that achieved by Tadoma users in tactual speech communication.     

Information relevance, working memory, and the consideration of alternatives

People routinely focus on one hypothesis and avoid consideration of alternative hypotheses on problems requiring decisions between possible states of the world--for example, on the “pseudodiagnosticity” task (Doherty, Mynatt, Tweney, & Schiavo, 1979). In order to account for behaviour on such “inference” problems, it is proposed that people can hold in working memory, and operate upon, but one alternative at a time, and that they have a bias to test the hypothesis they think true. In addition to being an ex post facto explanation of data selection in inference tasks, this conceptualization predicts that there are situations in which people will consider alternatives. These are:

1. “action” problems, where the alternatives are possible courses of action;

2. “inference” problems, in which evidence favours an alternative hypothesis.

Experiment 1 tested the first prediction. Subjects were given action or inference problems, each with two alternatives and two items of data relevant to each alternative. They received probabilistic information about the relation between one datum and one alternative and picked one value from among the other three possible pairs of such relations. Two findings emerged; (1) a strong tendency to select information about only one alternative with inferences; and (2) a strong tendency, compared to inferences, to select information about both alternatives with actions.

Experiment 2 tested the second prediction. It was predicted that data suggesting that one alternative was incorrect would lead many subjects to consider, and select information about, the other alternative. For actions, it was predicted that this manipulation would have no effect. Again the data were as predicted.     

The durations of attention to alternatives and re-evaluation in choices with two and three alternatives

In two experiments on choice the durations of attention to the alternatives were measured. In experiment 1 each subject chose one from two pictures; in experiment 2 the choice was one from three pictures. In both experiments the subjects understood that they would acquire the picture that they selected. In each experiment higher and lower conflict conditions were induced by offering subjects a choice between alternatives that had been evaluated either equally or disparately. In both experiments a significant relationship appeared between duration of attention and preference order with most subjects looking longest at the alternative that was preferred. In the comparison between conditions this effect was found to be stronger under lower conflict than under higher conflict; this difference reached a significant level in experiment 2. These results are contrary to findings by Gerard (1967), and this matter is discussed. The relevance of the results to other theories is examined. Inferences were drawn from dissonance theory about re-evaluation effects after decision, and evaluation changes were measured in the experiments. After adjustment for measurement regression, the data failed to reveal a significant chronic re-evaluation effect. Contrary to dissonance theory, the re-evaluation effect was weaker in the three-alternative choice experiment than in the two-alternative choice experiment.     

Independent alternatives

Philosophical Studies - Orthodox semantics for natural language modals give rise to two puzzles for their interactions with disjunction: Ross’s puzzle and the puzzle of free choice...     

Information transmission for one-dimensional stimuli: The role of strategies

Important evidence about the information flow between perceptual and motor processes has been obtained from the lateralized readiness potential (LRP) recorded in two-choice go/nogo tasks. Here, we investigated the effect of time pressure on information transmission for one-dimensional stimuli (four squares differing in size). In between- and within-subject designs, respectively, Experiments 1 and 2 showed that under time pressure partial information initiates hand decision and response preparation before complete size information is available. These findings appear to be at odds with the asynchronous discrete coding model. Experiment 3 assessed the mechanisms behind these effects by manipulating the relative difficulty of extracting hand- and go/nogo-specific information from the size of the stimuli. Consistent with asynchronous coding, our results suggest that serial-consecutive processes in extracting partial and full size information may occur also for one-dimensional stimuli. Our data are inconclusive as to the question of discreteness or continuity of information transmission. On a more general level, our data support the notion of flexibility in the coding of perceptual dimensions to adapt performance to environmental conditions.     

Framing effects in decisions with completely and incompletely described alternatives

Earlier research has shown that a variety of judgments depend upon how key sources of information are framed. Framing effects have been extended to include relative evaluations of stimuli with complete and incomplete information. The present study was designed to see if these effects are predictive of discrete choices and to isolate the locus of the framing effect. In Experiment 1 subjects were asked to indicate whether they would take each of a series of gambles described by payoff and probability information or by only one of these values. As predicted, subjects in the positive condition were more apt than subjects in the negative condition to take gambles when probability information was included, but not when it was missing. Subjects in Experiment 2 chose between gambles with complete and incomplete information. Consistent with the earlier findings, subjects in the positive condition were less apt than subjects in the negative condition to choose the gamble with missing probability information. Experiment 3 replicated the results of Experiment 2 while eliminating various psychophysical factors as causes of the framing effect. The way stimuli are framed appears to affect their subjective scale values and this determines both how they are responded to in an absolute sense and how they are compared to other stimuli.     

Selecting K of N alternatives

In some decision contexts (e.g. graduate admissions) the task to select a subset of k distinct alternatives from among the N > k > 1 options available. For moderate values of N and k, the number of possible subsets of size k becomes quite large. Assuming alternatives are evaluated using consistent, though not explicit weights, selecting k, rather than 1, empirically excludes a substantial proportion (more than 80%) of the subsets; unfortunately to the unaided decision maker it is not obvious which subsets should be excluded. The tendency of subjects to select excludable subsets can be called an ‘infeasibility’ bias. The experimental evidence surprisingly shows no ‘infeasibility’ bias, as subjects overwhelmingly chose non-excluded selections.