Analysis of weights in multiple observation tasks

Abstract

Multiple observation tasks are often used to investigate observers’ abilities to combine information from different sources or observations. This paper discusses a method for assessing the relative weight given to each observation. First, a theorem that derives the relative weights is stated. A technique for estimating relative weights is then illustrated by analyzing data from a multiple-tone task. In this task, observers listen to a sample of tones drawn from one of two distributions and decide which distribution was sampled. Results show that observers integrate information nonoptimally, attaching greater weight to the first and/or last observations than to observations occurring in the middle of the sequence. The generality of the technique is discussed.

Does a rhythmic context have an effect on perceptual weights in auditory intensity processing?

“…Note that the analysis is concerned with relative weights, for example, the question of whether the level of the first noise segment has a greater influence on the decision than the level of the fifth segment, regardless of the general strength of the association between the segment levels and the decision (cf. Berg, 1989).…”

“…This pattern is observed even if each segment provides the same amount of information concerning the correct response, so that the optimum response strategy would be to weight the level information provided by each temporal segment uniformly (Berg, 1989). Such a primacy effect could reduce the sensitivity of the procedure for detecting a change in the weights caused by the rhythmic context.…”

“…Common as this method is in the study of attention, there exists an alternative approach, which seems more appropriate for studying the direct perceptual consequences of rhythmic attention. In this study's Experiment 1, the influence of individual temporal portions of a longer sound on global loudness judgements (i.e., subjective magnitude) was measured by estimating the perceptual weight (Berg, 1989) each element received. Participants evaluated the overall loudness of a noise fluctuating in level.…”

“…In the rhythm condition, the noise was preceded by a short isochronous sequence of pure tones (rhythmic context sequence). Perceptual weight analysis was used (e.g., Ahumada & Lovell, 1971;Berg, 1989;Lutfi, 1992), for which a random variation is imposed on the individual components of a complex stimulus on each trial. In the present study, the components were the temporal segments constituting the level-fluctuating noise.…”

The optimum decision rules for the oddity task

“…Is the decision rule the optimum one for uncorrelated observations (£2 = 1), or does the observer use the triangular rule expressed by Frijters (I 979b)(£2 = O)? A technique recently suggested by Berg (1989), called the conditional on a single stimulus (COSS), may be useful in trying to answer these questions. We have not attempted to use the technique experimentally, but computer simulations of these two different decision rules suggest that it may be ofvalue.…”