delivered the opinion of the court:
After a bench trial, defendant, James Kerwin, was found guilty of three counts of aggravated criminal sexual assault in violation of section 12 — 14(b)(1) of the Criminal Code of 1961 (the Code) (Ill. Rev. Stat. 1989, ch. 38, par. 12 — 14(b)(1)). The trial court sentenced him to 15 years’ imprisonment. We affirm.
On appeal, defendant contends: (1) the trial court erred in assessing the credibility of the child witness; (2) defendant received ineffective assistance of counsel; and (3) the trial court considered improper aggravating factors in sentencing defendant.
On August 3, 1989, the State’s Attorney filed an information charging that defendant committed aggravated criminal sexual assault by placing his fingers in the vagina of his nine-year-old daughter, L.K. On December 12, 1989, the State’s Attorney charged defendant with two additional counts, stating that defendant placed his penis in U.K.’s vagina and in U.K.’s mouth. Defendant pleaded not guilty to all three counts but waived a jury, so the matter proceeded to a bench trial. In this appeal, a full recitation of the facts is unnecessary, and relevant facts will be included as we address the individual issues.
On appeal, defendant first contends that the trial court erred in assessing the credibility of the complaining witness, U.K. At trial, she testified that defendant touched her “between her legs” with his fingers, penis and tongue on numerous occasions starting when she. was seven years old and continuing for approximately two years. U.K. also testified that during that time her father made her put her mouth on his penis. In addition to U.K.’s in-court testimony, the trial court viewed two video-taped interviews of U.K. by Cecelia Rumney, youth and victims counselor for the Colorado Springs police department, where U.K. described the incidents of sexual abuse by defendant in greater detail. Defendant testified that although he accepted the fact that U.K. had been sexually abused, he was not the abuser. Defendant further testified that after he and his ex-wife, Rita Emig, had a bitter dispute, she threatened to prove defendant molested U.K. The court also heard testimony on behalf of defendant by Steve and Patrick Kerwin, two of defendant’s three *634sons, L.K.’s fourth-grade teacher, and Steve Kerwin’s girl friend. In reaching its decision, the trial court stated:
“THE COURT: Court, of course, has heard the evidence these last two days. Beginning with the testimony of [L.K.]. Court is convinced beyond a reasonable doubt that the defendant is guilty. There is no way a nine year old girl, girl that age can make up something like that. You know, this Court has been in court long enough, I am not saying I know every time someone is lying to the Court, I don’t.
But, I am confident in this case [L.K.] was telling the truth. You can not, the things that she could testify to are not within the experience of a girl that age, not only just the, the set of acts, but the whole totality of the circumstances. No one comes up with the fact, for instance, that they observe their father masturbating in front of them. It was something that is really not even related to this and yet the father has admitted to having done that when she was in the room, not being aware that she was awake. But, that basically, the whole nature of the case is disgusting. No way a nine year old, eight, nine, ten year old girl is going to come up with that type of evidence unless indeed it happened. There is no way that she is going to testify against her father, particularly especially one to whom she had a close relationship with unless it is true, unless there is some strong reason to try to get back for some reason. And there is absolutely no evidence of that, Court is convinced that the act of digital penetration, the act of penile penetration and the act of touching with the tongue did in fact occur within the period of time that the witness described.”
Defendant argues that the trial court relied upon the unsupported generalization that children cannot make false accusations of sexual assault, failing to assess L.K.’s individual credibility. In support of this argument, defendant cites numerous authorities which attest that children testifying about sexual abuse cannot be presumed credible just by virtue of their age and the subject matter of their testimony. This court does not dispute such an assertion. Clearly, it would be error for a fact finder to generally assume that every child under a certain age is incapable of fabricating incidents of sexual abuse. Although defendant would have us find that the trial court made such an improper assumption in the case at bar, we do not agree. As the State correctly points out, it is not improper for a fact finder to consider the sexual knowledge of the tes*635tifying child witness to determine if the knowledge is appropriate for a child of that age. (People v. Coleman (1990), 205 Ill. App. 3d 567, 563 N.E.2d 1010.) Admittedly, the trial court made some extraneous remarks regarding a nine-year-old girl’s sexual knowledge. Taken in the context in which those remarks were made, however, this court does not find that the trial court failed to properly assess L.K.’s credibility. The trial judge clearly stated: “I am confident in this case [L.K.] was telling the truth.”
A reviewing court has neither the duty nor the privilege to substitute its judgment as to the credibility of witnesses for that of the trier of fact. (People v. Novotny (1968), 41 Ill. 2d 401, 244 N.E.2d 182.) A finding based on the evaluation of the witness’ credibility will be sustained unless it can clearly be said that it was manifestly erroneous. (People v. Nelson (1974), 58 Ill. 2d 61, 317 N.E.2d 31.) In the case before us, the trial court heard testimony in support of defendant as well as L.K.’s testimony. The trial court found L.K.’s testimony to be more credible than defendant’s and defendant’s witnesses. The record shows that the trial court’s decision was affected by L.K.’s detailed account of the incidents of sexual abuse, but we do not find that the trial court relied on unsupported generalizations in its assessment of L.K.’s credibility. Therefore, this court will not disturb the trial court’s verdict.
We next turn to defendant’s contention that he was denied effective assistance of counsel. Defendant argues that defense counsel’s errors prejudiced defendant and denied him a fair trial in that defense counsel failed to object to inadmissible evidence and failed to secure defendant’s ex-wife as a witness.
The constitutionally guaranteed assistance of counsel has not been provided if defendant can prove counsel’s representation fell below an objective standard of reasonableness and that counsel’s shortcomings were so serious as “to deprive the defendant of a fair trial, a trial whose result is reliable.” (Strickland v. Washington (1984), 466 U.S. 668, 687, 80 L. Ed. 2d 674, 693, 104 S. Ct. 2052, 2064; People v. Albanese (1984), 104 Ill. 2d 504, 525, 473 N.E.2d 1246, 1255.) Defendant must establish that “there is a reasonable probability that, but for counsel’s unprofessional errors, the result of the proceeding would have been different.” (Albanese, 104 Ill. 2d at 525, 473 N.E.2d at 1255.) Judicial scrutiny of counsel’s performance must be highly deferential. Strickland, 466 U.S. at 689, 80 L. Ed. 2d at 694, 104 S. Ct. at 2065; Albanese, 104 Ill. 2d at 525, 473 N.E.2d at 1255.
*636Defendant argues that he received ineffective assistance of counsel because defense counsel failed to secure defendant’s ex-wife as a witness and failed to object to inadmissible evidence. In a post-trial hearing, defendant stated that his ex-wife probably would have testified against him. We find no reversible error in defense counsel’s strategy of not calling this adverse witness. Defendant also argues that defense counsel erred in not objecting to portions of the videotaped interview of L.K., expert testimony on post-traumatic stress syndrome, and hearsay testimony by some of the State’s witnesses. A thorough examination of the record reveals that the trial court based its decision on the credibility of L.K.’s testimony. Defendant does not dispute defense counsel’s performance in regard to that evidence. Defendant simply has not established that the result of the proceeding would have been different but for counsel’s errors. Therefore, we do not find that defendant received ineffective assistance of counsel.
Defendant’s final contention is that the trial court relied on improper aggravating factors in sentencing defendant to 15 years’ imprisonment. In sentencing defendant, the trial court considered it an aggravating factor that defendant’s conduct caused and threatened serious harm to L.K. Defendant argues that harm is inherent in the offense of aggravated criminal sexual assault and cannot be considered as an aggravating factor. Defendant’s argument is without merit. The statute under which defendant was convicted requires that the victim be under 13 years of age, that defendant be more than 17 years of age, and that an act of sexual penetration occur. (Ill. Rev. Stat. 1989, ch. 38, par. 12 — 14(b)(1).) Harm is not inherent in the offense. The determination and imposition of a sentence is a matter of considerable judicial discretion, and the standard of review is whether the trial court abused its discretion in imposing the sentence. (People v. Younger (1986), 112 Ill. 2d 422, 427, 494 N.E.2d 145, 147.) The statutory range of imprisonment for a Glass X felony is 6 to 30 years. (Ill. Rev. Stat. 1989, ch. 38, par. 1005 — 8—1.) In addition to the trial court’s consideration of the emotional harm suffered by the minor child, the trial court took into account the mitigating factors that defendant acted under strong provocation and relinquished his parental rights. Since harm is not inherent in the offense for which defendant was convicted, it was not improper for the trial court to consider the emotional harm suffered by the minor child as an aggravating factor. Therefore, we find no abuse of discretion in sentencing defendant to 15 years’ imprisonment.
*637For the foregoing reasons, the judgment of the circuit court of Clinton County is affirmed.
Affirmed.
MAAG,* J., concurs.