The cost of serially chaining two cognitive operations
 

Zhao Fan (1, 2), Krish Singh (3), Suresh Muthukumaraswamy (3), Mariano Sigman (4), Stanislas Dehaene (5) & Kimron Shapiro (6)*

(1) Key Laboratory of Adolescent Cyberpsychology and Behavior, Ministry of Education, 430079 Wuhan, China
(2) Central China Normal University, School of Psychology, 430079 Wuhan, China
(3) Cardiff University, CUBRIC, School of Psychology, CF10 3AT Cardiff, UK
(4) University of Buenos Aires, Physics Department, 1428 Buenos Aires, Argentina,
(5) Coll¨¨ge de France, 75005 Paris, France
(6) Bangor University, School of Psychology, LL57 2AS Bangor, UK

* Corresponding Author: Kimron Shapiro, School of Psychology, Bangor University, Bangor, Wales, UK LL57 2AS
Telephone: +44 (0) 01248 383626 Email: k.shapiro@bangor.ac.uk

Abstract

As Turing (1936) noted, a fundamental process in human cognition is to effect chained sequential operations in which the second operation requires an input from the preceding one. Although a great deal is known about the costs associated with ¡®independent¡¯ (unrelated) operations, e.g., from the classic psychological refractory period (PRP) paradigm, far less is known about those operations to which Turing referred. We present the results of two behavioural experiments, where participants were required to perform two speeded sequential tasks that were either chained or independent. Both experiments reveal the reaction time cost of chaining, over and above classical dual-task serial costs. Moreover, the chaining operation significantly altered the distribution of reaction times relative to the independent condition in terms of an increased mean and variance. These results are discussed in terms of the cognitive architecture underlying the serial chaining of cognitive operations. (Fan, Singh, Muthukumaraswamy, Sigman, Dehaene & Shapiro, 2011, Psychological Research).