Effects of Trial-Specific Verbal Descriptions on Matching-to-Sample Performances of Children and Adults

Transcription

1 EUROPEAN JOURNAL OF BEHAVIOR ANALYSIS 2008, 9, NUMBER 1 (SUMMER 2008) 29 Effects of Trial-Specific Verbal Descriptions on Matching-to-Sample Performances of Children and Adults Diana Moreno, Olivia Tena, Rosa María Larios, María Luisa Cepeda, Hortensia Hickman, Patricia Plancarte, Rosalinda Arroyo Facultad de Estudios Superiores Iztacala - UNAM and Daniel T. Cerutti Duke University Effects of verbal descriptions of stimulus relations on second-order identity matching were evaluated by arranging a sentence-completion requirement prior to matching a comparison to a sample stimulus. Sixteen college students (X=19 years) and 16 elementary school children (X=10 years) participated. Three experimental groups at each age were exposed to variants in the sentence completion format: descriptions of (1) matching contingencies, (2) relevant stimulus dimensions, or (3) choice performance. A control group had no exposure to sentences. Effects of verbal descriptions were evaluated on acquisition and transfer of matching. Across ages, experimental groups demonstrated higher accuracy during training and transfer tests. Between ages, adults matched more accurately than children; only control children never matched above chance. These findings are discussed in terms of the influence of verbal behavior on the acquisition and transfer of inductive repertoires in humans. Key words: Stimulus relations, matching-to-sample, second-order identity, inductive learning, transfer, verbal behavior, children, adults, humans. Human performances on schedules of reinforcement and conditional discrimination tasks have both revealed important influences of verbal behavior (e.g., Lowe, Beatsy, & Bentall, 1983; Matthews, Catania, & Shimoff, 1985; Devany, Hayes, & Nelson, 1986; Lowe, Harzem, & Hughes, 1987; Hayes, 1989; Horne & Lowe, 1996; Wulfert, Dougher, & Greenway, 1991; Cabello, Luciano, Gómez, & Barnes-Holmes, 2004). These experiments increasingly point to interactions between We are grateful for the technical assistance in programming the experiment lent by Carlos Martínez. Questions may be directed to the first author at, Facultad de Estudios Superiores Iztacala - Universidad Nacional Autónoma de México, Avenida de los Barrios No 1, Los Reyes Iztacala, Tlalnepantla Estado de México, C.P dianam@campus.iztacala.unam.mx 29 verbal and nonverbal behavior as a critical factor in understanding human behavior but the precise nature of this interaction and the appropriate methods for studying them remain a matter of debate (Shimoff, 1986). There are two main approaches to the problem. In the first, a participant is presented with a task and later asked to introspectively report on how they performed the problem (Critchfield & Perone, 1990; Ribes & Martínez, 1990). This approach is correlational, leaving open many questions about whether the post-session verbal behavior was actually occasioned by the nonverbal behavior or the post-session questionnaire (Shimoff, 1986). In the second approach, a participant s verbal behavior is manipulated like

2 30 Diana Moreno et al. any other independent variable and its effect on nonverbal behavior is directly measured (e.g., Catania, Matthews & Shimoff, 1982; Horne & Lowe, 1996). Qualitative differences in the matching-tosample performances of humans and other species have implicated significant contributions of verbal factors (Wulfert Dougher, Greenway, 1991; Dugdale & Lowe, 2000). In matchingto-sample, a participant is required to match a comparison stimulus to a sample stimulus on the basis of a conditional relation. In an identity relation, a sample is matched with the identical comparison (e.g., matching the letter A to A ); in a symbolic relation, a sample is matched with an arbitrarily related comparison (e.g., matching the uppercase A to a lowercase a ). With human participants, the training of symbolic relations can give rise to deductive emergent relations (Sidman, 1994). For example, after training matching of the comparison a to the sample A, humans typically demonstrate symmetry by matching A to a without further training (Sidman, Rauzin, Lazar, Cunningham, Tailby, & Carrigan, 1982). Failures of symmetry in nonhuman subjects have led to theories that humans provide the same names for samples and related comparisons, rendering them interchangeble (see review by Horne & Lowe, 1996). Support for naming theories in symbolic behavior is provided by findings that symmetry is more likely to emerge when names for symbolic stimuli are explicitly trained (Dugdale & Lowe, 1996). In addition, Wulfert et al. (1991), found that participants who verbally described relations between stimuli were more likely to show symmetry than participants who simply described stimuli. The learning of purely inductive stimulus relations as in generalized identity matching or concept learning has led to a different assumption about potential interactions between verbal and nonverbal behavior. Identity matching of a limited set of stimuli might be based on stimulus names but generalized identity matching, like a generalized repertoire of imitation (Baer, Peterson, & Sherman, 1967), may be too open-ended to be described by anything else than a general rule (e.g., Skinner, 1957, argued that abstraction was necessarily verbal). The possibility that verbal behavior interacts with identity or similarity relations between stimuli led studies in which verbal description of matching responses accompanied matching trials (Cepeda, Hickman, Moreno, Peñalosa, & Ribes, 1991; Fjelistrom, Born, & Baer, 1988; Ribes, Domínguez, Tena, & Martínez, 1992; Ribes & Rodríguez, 2001). Cepeda et al. (1991) presented college students with a mixed identity-similarity matching task (similarity relations are those in which stimuli are matched on the basis of shared features such as in a concept: e.g., Brown, 1989). Trials in the training phase consisted of matching stimuli along one of several dimensions, including color and form. Transfer tests following training included stimuli with novel dimensions such as number and size (for an analysis of identity generalization test procedures see Dube, McIlvane, & Green, 1992). In the experimental group, participants matching responses were preceded by unreinforced choices between multiple-choice statements describing the correct comparison; control participants matched without statements. Experimental participants showed the highest accuracy in matching and transfer, this suggest that simple verbal descriptions of matching responses could influence acquisition and generalization of inductive repertoires (for contrary examples in which verbal behavior interferes with inductive learning see Brown, 1989; Reber, 1976). Findings that descriptions of matching responses augmented identity and similarity matching performances led to questions about how a more complete description of the sample-comparison relations might influence matching (Hickman et al. 2001; Ribes, Moreno, & Martínez, 1995; Tena et al. 1997). Ribes et al. (1998) addressed this question with college students by employing a sentence-completion format superimposed on identity and similarity matching. In the experimental group, matching-to-sample trials were preceded by questions about trials such as, When appears above and appears below, I choose. Questions for experimental groups either asked about instances of matching or the class that

3 Descriptions of Matching 31 was being trained, while control participants had no questions. Accuracy between groups in participants final performances showed no effect of the type of question but control participants learned more slowly and were less accurate in transfer tests. However, Hickman et al. (2001) found that completing sentences describing the matching rule resulted in higher levels of matching and transfer accuracy than completing sentences describing instances of matching, corresponding to the findings of Wulfert et al. (1991) in the learning of deductive stimulus relations. If more general descriptions of matching are more likely to promote accurate performances and transfer, it follows that participants with more highly developed abilities to describe relational contingencies should also show more accurate matching abilities (Ribes, Cepeda, Hickman, Moreno, & Peñalosa, 1992; Tena, et al. 1997). In the case of deductive stimulus relations, experiments provide repeated demonstrations showing that relations such as symmetry are more likely to be found in participants with more advanced language skills (Devany, Hayes, & Nelson, 1986; Horne & Lowe, 1996; Wulfert et al. 1991). Tena et al. (1997) studied the case of inductive relations by relating college students abilities to describe the rules of Uno (Comercial y Facturera, S.A.: D.F., Mexico), a popular children s game involving identity matching of colors and numbers, to accuracy and transfer of identity and similarity relations. The findings paralleled those of Hickman et al. (2001) by showing that participants who described the game with general rules achieved higher levels of matching and transfer than participants who described the game by providing illustrative instances. Differences in execution and transfer in inductive matching tasks extend to experiments comparing children and adults. For example, Ribes et al. (1992) studied the effect of training matching to groups of college students and elementary-school children by presenting visual demonstrations of the matching performance, spoken instructions, or by combining visual demonstration with spoken instruction. Adults performed more accurately in training and on transfer tests presenting new stimuli with the same dimensions as trained stimuli (intradimensional tests) and novel dimensions (extradimensional tests); children showed marginal transfer in intradimensional tests and none in extradimensional tests. Of greater interest was the effect of training procedures. Adults benefited most from joint verbal-visual training while children benefited most from visual training alone. This finding suggests that spoken descriptions of matching contingencies can disrupt children s learning. To date, experiments on inductive matching tasks show that participants level of verbal development and the kind of verbal descriptions occasioned by a task influence both accuracy and transfer (Hickman et al. 2001; Ribes et al. 1992; Tena et al. 1997). Previous experiments found that adults perform more accurately when required to generate general descriptions of contingencies (Hickman et al. 2001), while children show interference by verbal instructions for matching (Ribes et al. 1992). The present experiment examined the effect of trial-specific questions pertaining to identity and similarity matching of stimulus relations in children and adults. In matching of stimulus relations, the sample stimulus consists of a pair of stimuli related by a dimension such as color, form, or symbol within a stimulus. The matching response involves choosing one of several pairs of comparison stimuli showing the identical relation, but different in form, color, or symbol to the sample, while distracter pairs showed other relations. For example in matching an identity relation, a sample consisting of two yellow squares with horizontal lines would be matched to a comparison consisting two purple circles with X s (i.e., both sample and comparison show an identity relation). In matching a similarity relation, a sample relating two stimuli by the color red but not their form or symbol would be matched to two blue stimuli with different forms and symbols (i.e., both sample and comparison show similarity in color). The question addressed by the present study was about whether matching of stimulus relations would be affected by controlling a par-

4 32 Diana Moreno et al. ticipant s abstraction of the matching problem s dimensions (Skinner, 1957). Abstraction was manipulated by presenting trial-specific questions about the basis of matching comparisons to samples. Three groups of adult and child participants were exposed to variations in multiple-choice question format as described in Table 3. The questions required participants to describe (1) matching stimulus dimensions, (2) relevant contingencies (cf., Fjelstrom, Born, & Baer, 1988), or (3) choice performance (cf., Hickman et al. 2001; Ribes et al. 1995). Table 3 provides an English-language translation of the Spanish questions used in the study with sample answers. Each type of question specifies a different level of abstraction entailed in matching of stimulus relations. A group design was employed to study this question because of its developmental nature (e.g., Bentall, Lowe, & Beasty, 1985), and because findings of previous conditional-discrimination studies, also employing groups, suggesting that instructional training procedures influence behavioral outcomes in ways that may not be reversible (e.g., Fjelistrom, Born, & Baer, 1988; Wulfert et al. 1991; Ribes et al. 1995; Hickman et al. 2001; Ribes et al. 2001). Method Participants Adult participants were 16 first- and secondsemester psychology students (3 males and 13 females) studying at UNAM-Iztacala, with a mean age of 19 years (range years, SD The student s coursework had not included learning about matching-to-sample behavior. Recruitment advertisement for students described the experiment as a study in learning. Child participants were 16 elementary school children (7 males and 9 females) attending a local mexican public school, with a mean age of 10 (range of years, SD.512), and were recruited for the study by their teachers. Children were informed that the study was a game in which they could earn food treats. College students received extra course credit for participation; children received candy. Participants were randomly assigned to experimental or control groups. Sessions were run daily except on weekends and in rare instances of absence from school. Setting and Apparatus Sessions were conducted in a sound-proof experimental room equipped with a table and chair, located on the UNAM Campus. A microcomputer placed on the table presented stimuli and collected data via the keyboard and computer mouse. Tasks were programmed with Toolbook software (Asymetrix Corp.: Bellevue: WA). Multiple-choice questions and matchingto-sample stimuli were presented on a VGA (33 cm diagonal) graphics monitor; responses to questions and stimuli mere made by pointing with the mouse and pressing the mouse button. Participants sat at the table facing the computer. Design Table 1 specifics the experimental conditions and transference tests sequence for each group. Procedure Participants were presented with a test for matching identity and similarity relations before and after exposure to procedures containing multiple-choice questions. Tests presented the relational matching task without multiplechoice questions and were used to measure the effect of training with questions. Following the training with questions, but prior to the post-test, three transfer tests were presented. The tests examined (1) intradimensional transfer with novel colors, shapes, and symbols, (2) extradimensional transfer with the same shapes and symbols but substituting size differences for colors, and (3) extrarelational transfer involving the training stimuli matched according to a difference relation. In matching a difference relation, a sample consisting of two stimuli with different colors, shapes, and symbols would be matched to a comparison consisting of two other stimuli with different colors, shapes, and symbols. The characteristics of stimuli in each condition are summarized in Table 2. General characteristics of the matching task remained the same throughout testing

5 Descriptions of Matching 33 Table 1. This table specifics the experimental conditions and transference tests sequence for each group. Groups DIM GROUP Adults and children Pretest Training Conditions Four sessions of 20 trials each one with feedback Matching repsonse plus refered texts to stimulus dimensions Transfer Tests One session of 20 trials each test without feedback Postest CONT GROUP Adults and children 20 Trials Similarity and Identity Shape, color and symbol without feedback Matching response plus refered texts to matching contingencies Intradimension Test Extradimension Test Extrarelation Test 20 Trials Similarity and Identity Shape, color and symbol without feedback PER GROUP Adults and children Matching response plus refered texts to choice performance CTRL GROUP Adults and children Without text, only matching response Table 2. Stimulus characteristics in training and test conditions. Condition Relation No Size (mm) Pre- and Post-Test Identity, Similarity red, yellow, purple STIMULI Colors Shapes Symbol circle, triangle, square X, Training Identity, Similarity red, yellow, purple circle, triangle, square X, Intradimension Test Identity, Similarity gray, green, brown diamond, pentagon, trapezoid >,! Extradimension Test Identity, Similarity 12 10, 18 gray circle, triangle, square X, Extrarelation Test Difference red, yellow, purple circle, triangle, square X, and training phases (with the exception of the multiple-choice training condition described below). Trials were initiated with the simultaneous presentation of a sample on the upper section of the screen, consisting of a horizontally-arranged pair of stimuli, and six pairs of comparison stimuli on the lower section of the screen. The six comparison stimuli, also horizontally-arranged pairs of stimuli, were presented in two rows of three stimulus pairs. All stimulus pairs were presented in individual black boxes to emphasize the groupings of stimuli. Participants chose between comparisons by placing the mouse pointer on a stimulus pair defined by a box and clicking the mouse button. There was no feedback during pre-post-, and transfer tests. During training conditions, correct choices were followed by Correct!

6 34 Diana Moreno et al. message and incorrect choices by Wrong! message. Feedback messages appeared on the lower section of the screen for two seconds. There was no correction procedure to repeat trials with errors. There was no inter-trial interval separating trials. Pre- and Post- Transfer Tests. Relational matching test sessions presented 30 trials in extinction and without a correction procedure. Participants were instructed that the first session required them to choose the stimulus pair at the bottom of the screen they felt best matched it. Sample stimulus pairs related form, color, and symbol, the relations of each type were presented in random order during the session. The five distracter stimuli were chosen randomly, the only exclusionary criterion was that they did not illustrate the relation displayed by the sample. Test sessions were preceded by a practice trial with instructions (English-language translations from Spanish are presented here). The instructions for the task were divided into four screens that were advanced by clicking the mouse button, as instructed. On the first screen, participants were informed: Seven pairs of figures will appear on the screen, one at the top of the screen and six at the bottom of the screen. Move the mouse pointer to the square that says Next Page for an example--just OBSERVE THE DISPLAY. The second screen displayed a typical matching trial as described above for the general task. When the participant cliking the mouse button on the Next Page button, the third screen displayed a typical matching trial screen. A button on the lower right screen requested the participant to View the next instruction. On the next page, participants were informed: Choose a pair of the figures below that best matches the upper pair by pointing to it with the mouse and clicking the left button of the mouse. You will not be informed if your choice is correct or incorrect. Move the mouse pointer to the square that says Next Page to practice. Clicking the mouse on the Next Page button produced a sample trial. A response to any of the samples erased the page and a final message appeared informing the participant that she could practice again or start the session. Relational Matching Training with Questions. The session following the pre-test exposed participants to the relational matching training procedure that included multiple-choice questions. Participants were informed that they would now receive feedback for their choices of comparison stimuli. Correct choices now produced the Correct! ; while incorrect choices produced the Wrong! message. Multiple-choice questions appeared in the middle portion of the screen, between the sample stimulus and comparisons. The question formats and sample answers are presented in Table 3. The correct answer to a question and distracter answers were presented below the question. There were seven distracters for the Table 3. Types of multiple-choice questions and sample answers for the three experimental groups and control group. Group Question Format Stimulus Dimensions The figures above similar in and different in (e.g., color (DIM GROUP) and symbol; form). Matching Contingences (CON GROUP) Choice Performance (PER GROUP) Control Group (CTRL GROUP) If are above, then (e.g., two figures with the same color, shape, and symbol; two figures with the same color, shape, and symbol). If appear above, I choose (e.g, : two figures with the same color, shape, and symbol; two figures with the same color, shape, and symbol) Without text, only matching response

7 Descriptions of Matching 35 Stimulus-Dimensions group, and 12 distracters for each of the Matching-Contingencies and Choice Performance groups (approximately twice as many distracters were required for these groups because Spanish grammar requires different articles and adjectives to correctly complete the first and second part of the question). Answers to questions were made by pointing and clicking on the answers with the mouse. Each question required the participant to select two texts, one for the first part of the question and a second for the second part of the question (see Table 3). There were no scheduled consequences for participant s answers to the multiple-choice questions. After selecting answers, participants were required to match one of the six pairs of comparison stimuli to the sample. Only the three experimental groups were presented with multiple-choice questions; control participants were only required to match comparison to samples with feedback for correct and incorrect matches (see Figures 1, 2 and 3). Training was conducted for four sessions of 20 trials each. At the end of each session the screen indicated the total number of correct answers for the session. Training sessions with multiple-choice texts were preceded by a practice trial with instructions. The instructions for the task were divided into four screens that were advanced by clicking the mouse button, as instructed. On the first screen, participants were informed: Seven pairs of figures will appear on the screen, one at the top of the screen and six at the bottom of the screen. In addition, a question and a series of answers to choose from will appear in the center of the screen. Move the mouse pointer to the square that says Next Page for an example--just OBSERVE THE DISPLAY. The second screen displayed a typical matching trial. The third screen provided instructions for choosing answers to the multiple-choice Figure 1.- Shows one typical trial to DIM Group (Stimulus Dimensions).

8 36 Diana Moreno et al. question and executing the matching response. Participants were informed: You must complete the questions by moving the mouse pointer to an answer that best fits and clicking the left mouse button. Remember that you must choose an answer for each blank. After answering, choose a pair of the figures below that best matches the upper pair by pointing to it with the mouse and clicking the left button of the mouse. In each trial you will be informed if your choice is correct or incorrect. Move the mouse pointer to the square that says Next Page to practice. The fourth screen contained a practice trial that required the participant to select answers to a question and to make a matching response. As in the actual training condition, feed back was arranged for the matching response but not for text selection. A sample response cleared the screen and allowed the participant to review the practice trial or start the session. Transfer Tests. At the end of the four training sessions the participants were presented with the three transfer tests described. Transfer tests consisted of 20 trials each and were presented sequentially on three separate days. The intradimensional test consisted of presenting examples of the training stimulus relations (identity and similarity) but with new figures, colors and symbols. The extradimensional test employed the training figures, symbols, and stimulus relations (identity and similarity) but the stimuli were now all the same shade of gray and appeared in two sizes (color was replaced by size). In the extrarelational test a novel relation of difference was presented using the training figures, colors, and symbols. Participants did not receive any feedback during transfer tests but they were informed of how many correct answers they had made after a session. Instructions for the three tests were the same as for the pre-test and post-test. Results The effect of different types of texts on relational matching is shown in Figure 4. This Figure 2.- Shows one typical trial to CON Group (Matching Contingences).

9 Descriptions of Matching 37 figure plots mean percent correct for adults and children in the four groups. Post-test results are shown in this figure indicate significant improvement in accuracy as a result of training in all but the control children. The effect of training conditions on relational matching was further evaluated by comparing pre-test and post-test accuracy with a three-way analysis of variance with two between- and one within- participant factors (age x group x test). In between- participant comparisons, there was a significant main effect for age [F(1,24)=17.10, p<0.001], a significant main effect for training condition [F(3,24)=6.42, p<0.005], and a significant interaction between age and group [F(3,24)=5.06, p<0.01]. In within- participant comparisons, there was a main effect for test [F(1,24)=398.98, p<0.001], no significant interaction between age and test, a significant interaction between groups and test [F(3,24)=5.76, p<0.005], and a three-way interaction between age, groups, and test [F(3,24)=13.32, p<0.001]. The last interaction suggested that training conditions had different effects on adults and children. Differences in test results were investigated by carrying out eight post-hoc comparisons (Scheffé, 95% confidence) for each of the pre- and post-test performances at each age. As suggested by Figure 1, these tests show a reliable difference in test results in all but the control children. Figure 5 shows the effect of training on matching response. Likewise the effect of training on response of matching was evaluated by comparing PER, DIM, CON and CTRL accuracy with a two-way analysis of variance with one between and one within participants factors (age x group). In between- participants comparisons, there was a significant main effect for age [F (1,30) = , p <.002], and age and group significant interaction [F (1,30) = , p <.000]. In within participant comparisons there was a main effect for group [F (3,90) = , p <.000], and a significant interaction between age and group [F (3,90) = 2.629, p <.05]. Once again, this interaction shows that training conditions had different Figure 3.- Shows one typical trial to PER Group (Choice Performance).

10 38 Diana Moreno et al. Figure 4. Shows mean percentage correct in Pretest and Postest for Dim, Per, Con and Ctrl Groups. effects in adults and children. A significant main effect was found between CTRL group and DIM group [F (1,30) = , p <.000], and CTRL group and PER group [F (1,30) = , p <.000], there was no significant difference between CTRL group and CON group. These different effects suggest that the performance is better when stimulus dimensions (DIM group) and choice performance (PER group) were described, than just matching response (CTRL group). Figure 6 shows the effect of training on transfer test, in terms of mean percent correct for adults and children. The effect of training conditions on relational matching was further evaluated by comparing intradimensional, extradimensional and extrarelational tests accuracy with a three-way analysis of variance with two between- and one within- participant factors (age x group x tests). In between- participant comparisons, there was a significant main effect for group [F(1,24)= 4.208, p<0.016], a significant main effect for age [F(1,24)=29.038, p<0.000], and a significant interaction between age and group [F(1,24)= 4.190, p<0.01]. In within- participant comparisons, there was not a Figure 5. Shows mean percentage correct during training for Dim, Per, Con and Ctrl Groups. Figure 6. Shows mean percentage correct in Training and Transfer tests, Intradimensional Test (INTRA-D), Extradimensional Test (EXTRA-D) and Extrarelational Test (EXTRA- REL) for Dim, Per, Con and Ctrl Groups.

11 Descriptions of Matching 39 main effect for test. No a significant interaction between age and test, and group and test. However, there was a significant interaction between extrarelational test group and age and extradimensional test [F(3,3)= 3.253, p<0.03]. Discussion This study explored acquisition and transfer differences in second order matching task, between children and adults who completed sentences by choosing texts referring to (a) stimulus dimension; (b) stimulus relations and (c) to own behavior. The impact of the completed sentences as verbal behavior effects, was shown by the substantial increase from the pretest to posttest correct responses in experimental children and adults groups. Particularly, the children control data support this since their posttest correct responses were so few, which points out the assumption about potential interactions between verbal and nonverbal behavior, in terms of abstraction behavior as Skinner (1957) argued. In the same way, the control groups performances during training and test sessions (see Figures 5 and 6), showed differential effects between adults and children participants, since the acquisition and transfer correct responses in the first one was identical in all experimental and control adults groups, whereas the children s performance in the control group were below of chance level in all training and test sessions. Ribes et al. (1992), Tena et al. (1997) and Hickman et al. (2001), point out that this differences are related with differential level of verbal development, while in children seems to be necessary an explicit training in described relations between verbal stimulus to show emergent behavior (like Wulfert et al. 1991; and Dugdale & Lowe, 1996), adults showed the verbal competence of abstraction without any explicit self-report training aid as completed questions choosing texts would be. In others words, contrary to children, adults did not required an external abstraction control of the matching-to-sample dimensions task (Skinner, 1957), but when this control was introduced (like the guesses questions), it did not interfere with matching performance and inductive generalization. Reber (1976) found adult s performance deteriorated when was exposed to explicit instructions. In the Reber s explicit instructions he asked at participants to identify rules from a complex system so they would be able to solve a memorization problem. He did not introduce verbal self-reports as in the present study. Our data showed that children benefited from choosing texts descriptions as rule-like conditions, in this sense we consider that some functional differences between instructions and descriptions as rule-like must be explored in terms of their impact of performance at different tasks (Cerrutti, 1989; Ribes & Martínez, 1990; Hickman, Morales, Cepeda, & Tena, 1990; Tena, 1994). The differences founded are attributable to experimental conditions and age. Ribes et al. (1995, 1998) found that adults matching accuracy was not affected by the kind of text introduced in the experimental conditions. However, in the present study, the differences on performance may be explained in terms of the nature of the texts used. All three kinds of text alluded to some kind of relation between stimuli pairs and differentiated one from the other kind of verbal responses displayed to be chosen (stimulus dimensions, stimulus relations and the own behavior). Relational texts similarly impacted subjects performance despite the verbal response they chose, so it seems necessary to explore the effect of self-report by controlling both the incomplete text and the class of textual options to be chosen. The kind of matching task also has to be considered in terms of its instructional possibilities. By example, in the second order-matching task each trial showed the rule to matching through a pair of stimuli. This pair of stimuli functioned like an instructional array and these make possible the generalization to new stimulus dimensions and instances. So, it can be said that adults subjects showed an inductive stimuli-function learning by matching stimuli relations (Hayes, 1989). Results confirm the relevance of verbal behavior on human subjects matching per-

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