The structure of sequential effects

Abstract

There is a long history of research into sequential effects, extending more than one hundred years. The pattern of sequential effects varies widely with both experimental conditions as well as for different individuals performing the same experiment. Yet this great diversity of results is poorly understood, particularly with respect to individual variation, which save for some passing mentions has largely gone unreported in the literature. Here we seek to understand the way in which sequential effects vary by identifying the causes underlying the differences observed in sequential effects. In order to achieve this goal we perform principal component analysis on a dataset of 158 individual results from participants performing different experiments with the aim of identifying hidden variables responsible for sequential effects. We find a latent structure consisting of 3 components related to sequential effects—2 main and 1 minor. A relationship between the 2 main components and the separate processing of stimuli and of responses is proposed on the basis of previous empirical evidence. It is further speculated that the minor component of sequential effects arises as the consequence of processing delays. Independently of the explanation for the latent variables encountered, this work provides a unified descriptive model for a wide range of different types of sequential effects previously identified in the literature. In addition to explaining individual differences themselves, it is demonstrated how the latent structure uncovered here is useful in understanding the classical problem of the dependence of sequential effects on the interval between successive stimuli.

Sequential Effects in SNARC

“…The pattern of results shown in Fig. 8 is known from the literature to be characteristic of 2AFC tasks with a very short response-stimulus interval (RSI) 29 , 30 and is thought to be associated with a response processing conflict in situations where there are delays in processing due to ageing or very high task demands 20 , 29 , 30 . This is a somewhat surprising finding as our experiment made use of a 1000 ms RSI, whereas profiles similar Fig.…”

“…However, sequential effects similar to those identified in RT have been observed in a multitude of different experimental measures, such as the point of subjective equality in psychophysical tasks 13 , 14 , event-related potentials in EEG 15 – 17 and prediction probability 18 . In addition, there is evidence for the existence of two components of sequential effects: one perceptual in origin and associated with the sequence of stimuli and another of motor origin and associated with the sequence of responses 13 , 17 , 19 , 20 .…”

“…Take the sequence XYXY for instance: applying the exponential filter to such a sequence results in p ( x t +1 = Y ) > p ( x t +1 = X ) since the two Y’s in the sequence were observed more recently than the X’s, despite the fact that the sequence is clearly alternating. However, in many circumstances humans not only display a sensitivity to alternations, but can even be more sensitive to alternations than repetitions 11 , 20 . In order to model this sensitivity to alternations several models include another type of exponential filter, similar in every respect to that in Equation ( 1 ) but applied to a binary sequence where each event represents either a repetition or alternation of the primary stimuli 22 , 24 .…”

Further tests of sequence-sensitive models in a modified Garner task using separable dimensions

“…Garner task with separable dimensions should be the same across the control, correlated, and filtering tasks. We might expect these sequential effects to look like the patterns associated with repetitions and alternations in simple 2AFC tasks (Gökaydin et al, 2016;Jones et al, 2013). Furthermore, Garner interference with integral dimensions arises in part due to the contributions of previous-to-current item similarity and due to the different configurations of similarity across tasks.…”

“…For instance, even if selective attention renders the correlated, control and filtering conditions equivalent to one another, one would still expect to see repetition effects as observed in the integral control task. One would also likely expect complex patterns of repetitions and alternations as demonstrated in several 2AFC tasks (Cho et al, 2002;Gökaydin, Navarro, Ma-Wyatt, & Perfors, 2016;Jentzsch & Sommer, 2002;Jones, Curran, Mozer, & Wilder, 2013;Soetens, Boer, & Hueting, 1985). In those tasks, there are two items, each associated with a separate response; the results are well-explained by assuming that people simultaneously learn about the base rates of each stimulus along with the rate of alternations (Jones et al, 2013).…”