A computational model to investigate assumptions in the headturn preference procedure.

Christina Bergmann,Louis Ten Bosch,Paula Fikkert,Lou Boves

doi:10.3389/fpsyg.2013.00676

Abstract

In this paper we use a computational model to investigate four assumptions that are tacitly present in interpreting the results of studies on infants' speech processing abilities using the Headturn Preference Procedure (HPP): (1) behavioral differences originate in different processing; (2) processing involves some form of recognition; (3) words are segmented from connected speech; and (4) differences between infants should not affect overall results. In addition, we investigate the impact of two potentially important aspects in the design and execution of the experiments: (a) the specific voices used in the two parts on HPP experiments (familiarization and test) and (b) the experimenter's criterion for what is a sufficient headturn angle. The model is designed to be maximize cognitive plausibility. It takes real speech as input, and it contains a module that converts the output of internal speech processing and recognition into headturns that can yield real-time listening preference measurements. Internal processing is based on distributed episodic representations in combination with a matching procedure based on the assumptions that complex episodes can be decomposed as positive weighted sums of simpler constituents. Model simulations show that the first assumptions hold under two different definitions of recognition. However, explicit segmentation is not necessary to simulate the behaviors observed in infant studies. Differences in attention span between infants can affect the outcomes of an experiment. The same holds for the experimenter's decision criterion. The speakers used in experiments affect outcomes in complex ways that require further investigation. The paper ends with recommendations for future studies using the HPP.

Highlights

Infants begin to acquire what will become their native language long before they produce meaningful speech themselves
The description of the results is split into two parts: First we describe the outcome of internal speech processing in the model in terms of familiarity scores
FAMILIARITY SCORES We first assess whether internal speech processing outcomes in the model can distinguish test sentences that contain familiarized words from sentences with novel words

Summary

Introduction

Infants begin to acquire what will become their native language long before they produce meaningful speech themselves. The HPP is based on the observation that infants tend to turn their heads toward interesting events. The time this headturn in maintained is interpreted as infants’ amount of interest. Jusczyk and Aslin (1995) demonstrated how the HPP can be used to investigate infants’ ability to memorize and recognize speech. Differences in the time the head is turned toward each of the two types of test stimuli indicate that infants process test stimuli with and without familiar words differently. Jusczyk and Aslin interpreted such listening time differences as the ability of the infants to discover that the familiarized words are present in some of the test sentences

Objectives

Methods

Results

Conclusion