Prepositions

Prepositions

Up to this point in teaching, the student has made several gains. Some of these gains, such as being able to identify and label concrete objects, may be viewed as relatively simple, whereas other gains, such as learning to express basic wants and needs and using language as it applies to abstract concepts such as colour, shape, and size, are considered more complex. Now, in acquiring prepositions, the student is taught certain abstract spatial relationships among objects or events. The Prepositions Program is potentially one of the most difficult programs for the student to master.

By means of the Prepositions Program, most students eventually learn that two objects can be described in terms of the spatial positions they possess relative to one another. For example, the student may learn to understand statements such as 'Place the pillow on the bed,' 'Put the milk inside the refrigerator,' or 'Please put a plate under your sandwich.' Many students also learn to express prepositional relationships, such as 'He is inside the house,' 'Trees have roots below ground,' 'Planes fly above the ground,' and '1 am standing on top of the stairs.' Equally important, many students learn to request certain arrangements, such as telling another person to sit close to her or to place a doll inside the toy house.

Psychologists and educators attribute many advantages to the acquisition of prepositional relationships. The acquisition of prepositions can help students orient themselves in space as well as in relation to other persons. These gains may aid in the student's development of individual boundaries, such as self-image or personal identity. Although behavioural psychologists do not use terms like self-image and personal identity, the concepts they represent are often used in everyday conversation such as when a person speaks of 'seeing herself in relation to another,' 'feeling outside the family,' and the like. An individual who is familiar with relationships among objects, individuals, and personal boundaries will converse more easily with others than persons who are not familiar with such relationships. Another advantage of learning prepositions is that prepositional relationships may later facilitate mastery of temporal or causal relationships

We begin this program by teaching the receptive identification of prepositional relationships. Once the receptive portion of the Prepositions Program is mastered, students are taught to express, or verbally describe, such relationships. The strategy of introducing novel material using receptive language prior to expressive language is a model adhered to in the preceding chapters. However, maintaining flexibility is important given that some students learn novel material more readily through the expressive format than the receptive format.

It is of the utmost importance that each team member working with the student acquires a thorough knowledge of discrimination learning procedures (Chapter 16) before the current program is introduced.

Receptive Prepositions

In the initial steps of this program, the student is taught to position an object in relation to another object. For example, the student is taught to respond correctly to your instruction 'On top' by placing an object, such as a block, on top of another object, such as a box or a bucket positioned upside down. The following materials are needed to teach prepositions: a small block, various small items (e.g., a toy car, figurines, a beanbag), a box or a bucket, two chairs, and a table of a size such that the student can place objects on top of it, climb on top of it, and fit underneath it.

Begin by having the student sit in front of the table and across from the teacher. Place a 12- to 20-inch tall bucket or box upside down on the table in front of the student. Note that the following steps all conform to the steps outlined in discrimination learning. Because it is difficult for most students to master prepositions, the steps involved in this program are described in some detail.

Step 1

Hand the student a block and mass trial SD1 ('On top'). Prompt the correct response by manually guiding the student to pick up the block, move the block toward the top of the upside-down bucket, and then release the block on top of the bucket. Reinforce. Begin fading the prompt by guiding the student's hand until it is positioned above the bucket and then letting go of the student's hand so that he releases the block independently. Fade the prompt further by guiding the student's hand toward the bucket and then letting go of his hand such that he needs to raise the block above the bucket and release it independently. Continue fading the prompt until the student picks up the block from the table and completes the entire action without assistance.

For some students, the teacher may want to employ a pointing prompt to aid the student's correct placement of the block. Do this by presenting SD1 ('On top') while pointing to the top of the bucket. The pointing prompt may help to bridge the gap between manually prompted trials and unprompted trials. If the student fails during prompt fading, go back a few steps and reinstate the level of prompting necessary to regain the student's success. Then begin the prompt fading process again. Be careful not to use inadvertent prompts such as looking at the top of the bucket while giving the SD or during the student's response. Place mastery at 5 out of 5 or 9 out of 10 unprompted correct responses.

Step 2

Perform mass trials of SD2 ('Beside') following the same procedures used for SD1 ('On top'). The use of the word 'beside' as SD2 should help to facilitate the discrimination between SD1 and SD2 because these SDs are composed of words that sound different from one another and consist of a different number of words. The placements of SD1 and SD2 are physically distinct from one another as well, which will further aid the student's discrimination between SD1 and SD2.

Immediately after presenting SD2, prompt the student's correct response by manually guiding him through the motions of placing the block beside the bucket. If further prompt-

ing is necessary after the manual prompt is faded, prompt by pointing to the correct location. Once the student performs 5 out of 5 or 9 out of 10 unprompted correct responses, go on to Step 3.

► Step

Within 2 seconds of completion of a correct response to SD2 ('Beside'), present SD1 ('On top') and simultaneously prompt the student's correct response. Fade the prompt and, after 3 correct responses in a row, switch to SD2 ('Beside'). Prompt the response, fade the prompt over successive trials, and secure 3 unprompted correct responses in a row before switching back to SD1 ('On top'). Next, alternate between SD1 and SD2 after 2 successive unprompted correct responses and then after 1 unprompted correct response. Provide an informational 'No' and withhold reinforcement for errors. As the teacher alternates between SD1 and SD2 and reinforces correct responses while not reinforcing incorrect responses, the SD1-R1 and SD2-R2 associations are strengthened and the SD1-R2 and SD2-R1 relationships are weakened. As the correct associations strengthen, randomly intermix SD1 and SD2 to prevent a win-stay or lose-shift pattern of responding. Set mastery at 9 out of 10 or 19 out of 20 unprompted correct responses.

Once mastery of the discrimination between SD1 and SD2 is achieved, we recommend that this discrimination be generalized across several team members and different locations around the house over the next 3 or 4 days. This is consistent with earlier recommendations concerning the first discrimination and newly established discriminations achieved within a program. This first discrimination should be solidified because doing so facilitates the student's acquisition of new prepositional relationships.

Select a third preposition that is as different from the first two as possible. 'Next to' may not be easily discriminated from SD2 ('Beside') due to its similarity in positioning. 'Under' may be more discriminable although the student may be distracted by the need to use two hands to complete the response to this SD: one hand to lift up the bucket and the other hand to put the block underneath the bucket. Finally, 'Behind' is not a good choice for SD3 given that it sounds fairly similar to SD2 and the student cannot observe the eventual placement of the block. 'In front' may be the best choice for SD3 given that only one hand is required for performing the response, the words composing the SD sound different from the former SDs, and the placement of the stimuli will be observable and relatively discriminable from SD1 and SD2.

► Step 4

Present mass trials of SD3 ('In front'). Prompt the correct response (placing the block in front of the bucket) and reinforce as done in Steps 1 and 2. Gradually fade the prompt(s). Once SD3 is mastered (5 out of 5 or 9 out of 10 unprompted correct responses), intermix SD3 with SD1 ('On top'). Once the intermixing of SD3 with SD1 is mastered (9 out of 10 or 19 out of 20 unprompted correct responses), move on to intermixing SD3 with SD2.

In addition to practicing these new discriminations, be sure to practice the SD1-SD2 discrimination, which may have been partially lost in establishing SD3. Note also that we recommend stopping at three prepositions at this time and further strengthening the student's mastery of these prepositions by introducing the next phase of the Program: Generalizing Prepositions Across Objects.

Generalizing Prepositions across Objects

Up to this point, the student has gone through several steps of the Prepositions Program. The student first learned to place an object (a block) on top of another object (a bucket). The student was then taught to position the block beside the bucket and discriminate between placing the block on top of and beside the bucket. The student was also taught to place the block in a third position ('In front') in relation to the bucket. Finally, the student learned to discriminate the third position from the first two.

Despite all this training, it is likely that the student will need further help in discriminating prepositions when different objects are used and different teachers present the instructions. That is, the student may have been inadvertently reinforced for attending to a very specific and idiosyncratic feature of a particular object or to certain auditory or visual cues unique to a particular teacher. To avoid such a narrow understanding of prepositional relationships, we recommend introducing new teachers (e.g., family members) and extending the number and variety of objects to be placed and objects to be referenced for placements. To facilitate the illustration of steps needed to accomplish this skill, we use the term placement object to refer to the object that is placed (moved into position) and the term target object to refer to the object that receives the placement object. In the previous section, the block was the placement object and the bucket was the target object. In the following steps, the target object may be varied by using such items as a different looking bucket, then a shoebox, and then a big coffee mug. Similarly, the original placement object (the block) may be varied by using such items as animal figures, toy cars, spoons, and beanbags.

Prior to beginning the steps presented below, the student should have been taught to identify (e.g., point to or touch) the new target and placement objects by following the procedures described in the Receptive Identification of Objects Program (Chapter 17).

Step 1

Generalize placement objects. Using the bucket as the target object, change the placement object to, for example, a toy car, then a beanbag, and then an animal figurine. Once the student is able to position novel placement objects on top, beside, and in front of the target object on the first trial, move on to the next step.

Step 2

Position two or more placement objects in front of the student (e.g., a toy car and the original block) so they are side by side, about 8 to 10 inches apart. As a pre-training step, make certain the student can correctly identify (by pointing to or touching) each object when they are displayed concurrently on the table. Next, instruct the student to place one of these two objects on top of the bucket. For example, instruct, 'Car on top,' emphasizing the word 'car' to facilitate the student's correct response. Prompt if necessary (e.g., with a position prompt), reinforce, and fade the prompt. Once the student achieves mastery (5 out of 5 or 9 out of 10 unprompted correct responses) with 'Car on top' as the SD, change the SD to 'Block on top' and establish correct responding. Finally, randomly rotate 'Car on top' and 'Block on top' by following discrimination learning procedures.

Step 3

Slowly increase the number of placement objects displayed concurrently on the table from two to five or six, first making certain that the student can identify each one of them receptively. Vary the instructions as needed to form the appropriate SDs for each of the different objects.

Step 4

Teach the second and third prepositions ('Beside' and 'In front') while retaining the same placement objects and target objects used in Steps 1 and 2 of this section. The student now must identify the correct placement object and discriminate among prepositions. This is an example of a simultaneous discrimination and shows how the program progresses in complexity in a gradual manner, which an appropriate manner is considering the difficulties most students experience when attempting to master prepositional relationships. Set mastery at 5 out of 5 or 9 out of 10 unprompted correct responses in trials that involve the random rotation of the placement objects and the three locations ('On top,' 'In front,' and 'Beside').

Step 5

Generalize target objects. Using the same placement objects introduced in previous steps, change the target object by removing the bucket and replacing it with a box. Note that the student should have previously mastered receptive identification of both the bucket and the box. Once mastery is achieved (5 out of 5 or 9 out of 10 unprompted correct responses) using the box as the target object, go on to Step 5.

Step 6

Position two target objects (the bucket and the box) side by side on the table (about 1 foot apart) and place one of the placement objects (e.g., the block) on the table such that it is equidistant from both the bucket and the box. Teach the student to place the block on top of the box in contrast to on top of the bucket, emphasizing the words 'bucket' and 'box' in their respective instructions to help facilitate the discrimination.

After mastery is reached using the block as the placement object, add a second placement object (e.g., a toy car) and teach the student to discriminate among the four possibilities: SD1 ('Block on top of bucket),' SD2 ('Car on top of bucket'), SD3 ('Block on top of box'), and SD4 ('Car on top of box'). Once the student masters the discriminations among these SDs, teach the second preposition ('Beside'). At this stage, there are eight discriminations ('Block on top of bucket,' 'Block beside bucket,' 'Block on top of box,' 'Block beside box,' and the same positions but involving the car). Further discriminations may be taught by introducing the third preposition ('In front'). Mastery of these discriminations necessitates that the student makes a triple discrimination; that is, the student must choose between target objects, placement objects, and prepositions.

It was earlier advised that generalization training should be employed across teachers and environments after the first discrimination (between 'On Top' and 'Beside') was mastered. The same advice should be followed after each discrimination. With increasingly large numbers of prepositions, there is a concomitant increase in risk of interference from idiosyncratic expressions and teaching styles across teachers. Be patient and proceed gradually. Generalization training will solidify the discriminations, facilitate their functional and practical properties, and improve the student's recall.

Areas of Difficulty

With this program, the student is confronted with very difficult learning tasks. It is important to keep in mind that even for those students who move relatively quickly through the beginning stages of this program, mastery of the discriminations may take some time.

Sometimes a teacher gets carried away when teaching a particular program, such as prepositions, and involves the student in that program at the expense of other programs. A fast-moving learner may make a promising (and, to the teacher, reinforcing) start; only to become overwhelmed by all the various combinations and permutations involved in using several placement objects, several target objects, and several prepositions. It is therefore important to set aside a limited amount of time for teaching prepositions once the basic steps are mastered. It is essential to intermix sessions of prepositions with sessions of easier tasks, such as nonverbal imitation and matching, as well as tasks placed on the maintenance schedule. Through the intermixing of programs that help the student succeed, a high level of motivation is maintained, boredom is averted, and frustration is reduced.

Individual differences among students are as pronounced in the Prepositions Program as they are in any other program. Students vary enormously in their rate of acquisition of the receptive prepositions presented thus far. Our experience is that a small minority of students master the use of receptive prepositions by the end of 1 month. Many students, however, do not master receptive prepositions even after 2 years of intensive teaching.

Some students experience considerable difficulty with the initial discrimination in the Prepositions Program. If this occurs, intermix SD1 ('On top') with a contrasting stimulus that may later facilitate the SD1-SD2 discrimination. The contrasting stimulus could be chosen from the Nonverbal Imitation Program or any of the receptive language programs. In addition, the response to the contrasting stimulus should be kept simple (e.g., imitating your clapping hands or touching the table).

To use a contrasting stimulus to facilitate the student's discrimination, first present SD1 ('On top') and reinforce the correct response. Then introduce a contrasting stimulus (SDCS) that is nonverbal in nature (e.g., imitation of your clapping hands), intermixing SD1 and SDCS according to the discrimination learning paradigm. Once the student masters the intermixing of SD1 ('On top') and SDCS in random rotation, you may want to further facilitate the acquisition of the target discrimination by introducing an SDCS that, like SD1, has a verbal component. For example, contrast SD1 with an SDCS such as 'Touch nose.' This contrast should be more difficult than the contrast between SD1 and the nonverbal imitation SDCS because both SDs contain auditory cues. Subject SD1 and the new SDCS to discrimination learning procedures until the student performs correctly in 5 out of 5 or 9 out of 10 unprompted trials. Once the student can discriminate SD1 from a contrasting stimulus, return to the SD1-SD2 discrimination.

Another potentially helpful procedure for the student who has difficulty with the initial discrimination is using two different placement objects for each of the first two prepositions and then fading out one of these objects. For example, use a red block for 'On top' and a white block for 'Beside,' or use a block for 'On top' and a beanbag for 'Beside.' The target object (a bucket) should be kept constant. Any deviation (of colour, size, or shape) in stimuli that may facilitate the student's discrimination is considered to function as a prompt. As always, the disadvantage of using prompts involves teaching prompt dependency.

Therefore, fade all prompts as soon as possible and remember to keep an eye out for inadvertent prompts. For example, after giving the SD, do not inadvertently prompt the correct response by looking toward the area in which the placement object should be positioned. Although it may be tempting to encourage the student through the use of such prompts, remember that, once mastery of a skill is reached without prompts, it is easier for the student to acquire new skills within the program.

A problem that can occur when only two responses are targeted at a time is that the student may fall into a win-stay and lose-shift pattern of responding. In other words, if the student gets one response wrong and misses out on reinforcement, the student may switch to the other response on the next trial without listening to your instructions. To prevent such a pattern from occurring, adhere to random rotation once this step is reached in discrimination learning.

Other problems may occur because of the stimuli themselves. For example, a particular toy used as a placement object may invite self-stimulation. Another possibility is that the response the student learned with the block and bucket in the first hours of treatment (placing a block in the bucket) may interfere with correct responding in future programs that involve these same stimuli. If either of these problems occurs, replace the block with a beanbag; change the bucket to a box, or both.

For some students, it may be easier to position them.' selves in relation to an object rather than position two objects in relation to each other (see the later section, 'Receptive Prepositions In Vivo'). For example, the student may have less difficulty learning to place him on top of or under a table than placing a block on top of or under a bucket.

If all else fails, withdraw the Prepositions Program for a month or more and then reintroduce it at a later time. This is good advice for students who encounter serious difficulty in any program. Sometimes intervening programs facilitate mastery of later or reintroduced programs.

Expressive Prepositions

We advise that you begin teaching receptive prepositions in vivo as the receptive prepositions using objects format nears mastery. However, we introduce the early stages of the expressive format at this point because the prior mastery of receptive prepositions may facilitate the student's acquisition of expressive prepositions. Regardless of which format is started first, we suggest that you practice receptive prepositions in vivo between sessions of expressive prepositions.

The student should have mastered verbal imitation and made significant progress in expressive labelling (Chapters 22, 23, and 24, respectively) before beginning the expressive component of the Prepositions Program. Begin by teaching the student to verbalize the prepositional relationships taught in the receptive format, and initially keep the expressive labels simple (e.g., 'On top'). Later, by adding verbs such as 'is,' you can start teaching sentence structure (e.g., 'Block is on top of bucket'). These sentences can then be built upon through the addition of pronouns, extended to an in vivo format, and generalized to everyday life as expressed in sentences such as 'I am standing on top of the table,' 'I am sitting between Mom and Dad,' and 'My school is next to the park.'

There are at least two ways to approach the teaching of expressive prepositions. You can give the receptive instruction first (e.g., 'On top') and then ask the student, 'Where is it?' and teach the student to answer, 'On top.' Alternatively, you can delete the receptive phase and present the student only with the physical arrangement (e.g., with the block on top of the bucket) and then ask, 'Where is it?' prompting the correct verbalization and reinforcing as described in the expressive labelling programs. We outline the steps for teaching the latter procedure first.

Step 1

Start the expressive component of this program by arranging the teaching environment in the same manner and with the same stimuli used in teaching receptive prepositions. Distinctly place the block on top of the bucket and then give the verbal SD ('Where is it?'). Immediately after giving SD1, prompt and reinforce the student for responding with a short label (e.g., 'On' or 'On top'). Mass trial SD1 and systematically fade the prompt. Place mastery at 5 out of 5 or 9 out of 10 unprompted correct responses.

Step 2

Place the block beside the bucket and give the instruction 'Where is it?' Immediately after giving SD2, prompt the correct response 'Beside.' Mass trial SD2 while systematically fading the prompt. Place mastery at 5 out of 5 or 9 out of 10 unprompted correct responses.

► Step 3

Intermix SD1 and SD2 according to discrimination learning procedures. Place mastery at 9 out of 10 or 19 out of 20 unprompted correct responses. Once the discrimination is established between SD1 and SD2 in this controlled environment, strengthen the discrimination over the next 2 to 3 days by extending it across persons and environments. Also, generalize the first expressive prepositions by using different objects as was done in the receptive format. Once the student demonstrates mastery of the SD1SD2 discrimination, introduce SD3 using the procedures described in Steps 1 and 2. Once SD3 is mastered in mass trials, intermix it first with SD1 and then with SD2. Finally, teach the student to discriminate among all three SDs.

Up to this point, a maximal prompt has been used: You have directly prompted the correct response by stating, 'On top,' 'Beside,' and so on. As mentioned earlier, however, your receptive instruction may also prompt the student's expressive label. At some point into the program, you may probe such a prompt by giving the student the placement object and presenting the receptive SD 'On top' in a loud voice. Immediately after the student's correct placement, quickly ask, 'Where is it?' If the student fails to respond correctly, consequate the response and then prompt the next trial by saying, 'On top,' fading this prompt over subsequent trials. We recommend using receptive instructions as prompts at some stage in learning since this kind of prompt is less intrusive than a full verbal prompt and is more likely to be used in everyday life.

A minority of students (approximately 2 out of 10) master an additional three to four expressive prepositions within the same week of having mastered the first two prepositions. However, for the majority of students, we recommend holding off on new prepositions, introducing them one at a time and intermixing them after the first three prepositions are generalized across persons and environments and practiced in vivo. By following this advice, the gains made are transferred to a student's everyday environment and serve the functional purpose of helping the student achieve better adjustment in day-to-day living. This adjustment, in turn, will likely reinforce and maintain the student's mastery of prepositions.

Receptive Prepositions in Vivo

We recommend that you start the Prepositions Program with a 'contrived' environment (with a block, a bucket, and the student seated at a table) in order to simplify the teaching environment and achieve better control over the variables involved in the teaching situation. For this part of the program, the student should participate more actively in prepositional relationships. Start this task in the receptive format by asking the student to position herself in relation to some object. For example, the student may be asked to place herself on top of the table, beside the table, in front of the table, and under the table. This skill is then extended to other items, such as a bed, a chair, and another person. To start, you and the student should stand approximately 2 to 3 feet apart, side by side, in front of the student's table.

Step 1

Present SD1 ('On top') and physically prompt the student to climb on top of a low table. Reinforce the response. Help the student down from the table. Then repeat SD1, fading the prompt over subsequent trials. It may be helpful to gradually transfer to a less intrusive prompt, such as pointing to the top of the table, which is easier to administer and fade than a physical prompt. Mass trial SD1 and place mastery at 5 out of 5 or 9 out of 10 unprompted correct responses.

Step 2

Present SD2 ('Under') and prompt the correct response as done in Step 1. Fade the prompt. Place mastery at 5 out of 5 or 9 out of 10 unprompted correct responses.

Step 3

Intermix SD1 and SD2 according to discrimination learning procedures. Place the criterion for mastery at 9 out of 10 or 19 out of 20 unprompted correct responses. Once the two prepositions 'On top' and 'Under' in relation to the table are mastered, generalize these prepositions from the table to other target objects. For example, teach the two prepositions in relation to a chair, a bed, and other objects in the house that allow for the teaching of 'On top' and 'Under.' We recommend solidifying the mastery of these

two receptive prepositions over the next several days, generalizing them across team members, before going on to additional in vivo receptive prepositions (e.g., beside, behind, in front). Some students enjoy being actively involved in learning and thus may be more motivated to learn through in vivo formats.

Expressive Prepositions in Vivo

Once the student masters two or three receptive prepositions in vivo, begin teaching their expressive counterparts. The SD for expressive prepositions in vivo consists of the question 'Where are you?' and the student's position in relation to a target object, such as a piece of furniture (e.g., a table). The teaching situation should be arranged in the same manner that was used to teach receptive prepositions in vivo.

Step 1

Give the receptive instruction 'On top' in a loud and clear voice or place the student on top of the table. Once the student is in position, present the verbal component of SD1 ('Where are you?'). If necessary, prompt the correct response by using a full verbal prompt, requiring only the short verbal response 'On top' at this point. Reinforce the response. Repeat the trial. Remember to remove the student from the table between trials and position him on top of the table with each presentation of SD1. Bring to the mastery criterion of 5 out of 5 or 9 out of 10 unprompted correct responses.

Step 2

Instruct the student, 'Under,' or place him under the table. Next, present the verbal component of SD2 ('Where are you?') and immediately prompt the student's response. Reinforce. Set mastery at 5 out of 5 or 9 out of 10 unprompted correct responses.

Step 3

Intermix SD1 and SD2 according to discrimination learning procedures. Once discrimination between SD1 and SD2 is mastered, generalize it across teachers. Then introduce the third expressive preposition (e.g., 'Beside') using the procedures just described.

In the beginning stages of teaching the student to label prepositions, do not require a complex answer. An example of a complex response is 'I am standing on top of the table.' By requiring such an answer, you may inadvertently attempt to teach two behaviours at the same time (i.e., expressive prepositions and sentence construction), a procedure that is likely to interfere with the student's mastery of prepositions. It is the prepositions themselves (e.g., on top, under, beside) that are targeted in the Prepositions Program; sentence construction should be taught separately. Thus, in the initial stages, require only the most important element (i.e., the actual preposition) and teach the student to elaborate on the answer in sentence form at a later stage.

Generalizing In Vivo Prepositions

When generalizing prepositions, the student should be taught to answer questions such as 'Where are you?' while she is in various environments. To achieve generalization, walk the student to different positions in relation to individual objects (e.g., a table, a chair, a bed, a car) and give the SD ('Where are you?'). Prompt the correct answer if necessary. It may be helpful at this point to use the receptive mode as a prompt for the expressive mode. For example, give the SD ('Sit inside the car') and, once the student is in position, present the SD ('Where are you?'). Verbally prompt the correct answer if necessary. Again, remember that all prompts must be systematically faded. That way, when asked, 'Where are you?' in everyday situations, the student is able to provide the correct answer independently. Generalize prepositions one at a time and teach the student to discriminate among them in different settings by following the methods described earlier in this chapter and in the discrimination learning chapter.

Concluding Comments

We have advised teaching two or three prepositions involving everyday objects in the receptive, expressive, and in vivo formats. Once these few prepositions are mastered, we recommend teaching one new preposition per month so that ample time is left to solidify the student's mastery of these prepositions and to teach the many other programs the student needs to master. Prepositions are abstract concepts, and mastery of prepositions may conceivably facilitate the student's later acquisition of other abstract concepts, such as pronouns and causeeffect relationships. No empirical data as of yet, however, suggest that such transfers of learning occur.