This small scale study replicates an earlier more detailed study ‘the cascade model’ by Humphreys, Riddoch & Quinlan, (1988), comparing recognition times with correct responses to structurally similar (SS) objects and structurally distinct (SD) objects. The purpose of this study was to examine the time differences between recognising SS and SD objects. In order to do so participants were shown 32 simple line drawings (randomly presented 16 SS and 16 SD objects) and using a SUPERLAB computer programme the recognition times of each object were calculated.

The results demonstrated that, in correspondence to Humphreys et al. (1988), reaction times for SS objects were longer than SD objects. Furthermore it was revealed that there was enough data to make a valid statistical analysis on errors and it was found that SD objects resulted in more errors than SS objects. It is considered that response competition and competing information in recognising SS objects is the explanation for it being more difficult and therefore longer to discriminate between compared to SD objects (Gerlach, Law, Gade & Paulson, 1999).

Introduction

The study of perception gives insight to how we construct a conscious representation of our surrounding environment and how we process and use our conscious experience to recognise objects and object relationships (Coren, Ward & Enns, 1994). Object recognition is a complex process and pictures are of important focus in the psychology of perception; this is demonstrated in many studies with the use of simple line drawings (Humphreys et al. 1988; Humphreys & Forde, 2000; Gerlach et al. 1999; Snodgrass & Vanderwart, 1980), these studies collectively, give good understanding in explaining the difficult processes involved in how we interpret and differentiate specific objects.

Knowledge and past experiences enable us to categorize objects according to particular characteristics. This facilitates different representations of different objects and is stored in memory in many forms which are thought to be designed to aid memory recall. Consequently, objects are recognised from impressions, or schemas, and categories with similarities. Collins and Quillian (1969; cited in Hayes, 2000) advocated that impressions are stored hierarchically, from general to specific features and the time taken for identification is dependent on the number of decisions or identification nodes implicated to name an object. They concluded that the more features displayed, the less decisions made and therefore more immediate object recognition.

Humphreys et al. (1988) proposed the ‘cascade model’ and suggested that there are two types of objects in our surrounding environment; the separation is based on perceptual form. It is explained that with natural and artefact categories, most natural objects belong to SS categories and most artefact objects belong to SD categories. By means of the cascade model it is alleged that the information processing to differentiate and name objects is transmitted continuously through a system of three stages; the structural description system, the semantic system and finally the level at which the activation of semantic description extends to phonological description specifying object names, thus leading to a ‘cascade’ of decisions.

The ‘cascade model’ suggests that recognition of SS is a longer process than for SD objects (Humphreys et al. 1988). In support of this suggestion it was also deliberated by Gerlach et al. (1999) that with SS objects, there is response competition and competing information to select from, making it more difficult and longer to discriminate between compared to SD objects. As a means of testing these proposals and in attempt of providing further support, the present experiment intends to some extent replicate, on a smaller more specific scale, the detailed study of the cascade modal by Humphreys et al. (1988).

The primary experimental hypothesis states that the recognition times with the correct response for SS objects will be significantly longer than the recognition times with the correct response for SD objects. The null hypothesis states that there will be no significant difference in recognition times with the correct response between SS and SD objects. Furthermore, on completion of the experiment it was revealed that there was enough data to make a valid statistical analysis on errors and therefore an additional hypothesis is there will be a significant difference in errors between SS and SD objects and a null hypothesis stating there will be no significant difference in errors between SS and SD objects.

Method

Design

The independent variable was the ‘type of object’ displayed (with two levels, SS and SD objects), and the major dependant variable was the average correct ‘recognition time’ (in milliseconds (ms)). On completion of the experiment an additional dependant variable was ‘error rates’ for SS and SD objects. The design utilised to test the hypothesis and analyse the data was a within subjects paired sample, related t-test where outliers (time taken over 1000 ms) were removed for more accurate results.

Participants

Each student carrying out this study selected 2 participants, the total number of participants was 272 mixed gender associates, all of which were na�ve to the psychology of perception and agreed to take part on a voluntary basis.

Apparatus

The running of this experiment was conducted using a computer software programme named SUPERLAB; this programme is designed to run simple psychology experiments. Using this software each participant was shown, on screen, 32 randomised line drawings (see appendix 1) of SS and SD objects (16 of each condition, one at a time) and their response times were calculated. A response table was used by the experimenter to record correct and incorrect responses for further analysis (see appendix 2) and a memory stick was used to save the results.

Procedure

An experimental instructions sheet was read (see appendix 3). A memory stick was inserted into the computer in order to save the collected data and the SUPERLAB programme was started up (see appendix 4). Each participant was read a set of instructions (see appendix 5) before the experiment explaining the procedure they were expected to follow. When each subject was ready they were given a small practice block to make certain they understood the task. On satisfactory completion of the practice run subjects were asked to press the space bar and wait for the display of the ‘fixation cross’. This was the focus point of which participants were asked to gaze upon and wait for the presentation of each line drawing. As soon as a line drawing appeared the computer timer started, each subject was instructed to press the ‘Y’ key the moment they recognised the object (the timer stopped and the screen went blank) and outwardly name the object.

Each name given was noted and recorded in a response table for further analysis (see appendix 2). Again when ready, the participant pressed the space bar for the next object and this course of action was repeated for all 32 experimental objects (randomly presented 16 SS and 16 SD). Each participant was asked if there were any line drawings they found particularly difficult to recognise and name. The data was saved (see appendix 6) as an excel document where it was put in chronological order and all naming errors were removed to calculate the average recognition time for SS and SD objects. All naming errors were reported at the bottom of the excel document. The completed document was submitted for collation with the remainder of the years’ results (see appendix 7).